Jivan S. Parab
Vinod G. Shelake
RajanishK.Kamat
Gourish M. Naik
A Hands on Approach
EXPLORING C FOR MICROCONTROLLERS
Exploring C for Microcontrollers
A Hands on Approach
JIVAN S. PARAB
Goa University
India
VINOD G. SHELAKE
Shivaji University
Kolhapur, India
RAJANISH K. KAMAT
Shivaji University
Kolhapur, India
and
GOURISH M. NAIK
Goa University
India
4y Springer
A C.I. P. Catalogue record for this book is available from the Library of Congress.
ISBN 978-1-4020-6066-3 (HB)
ISBN 978-1-4020-6067-0 (e-book)
Published by Springer,
P.O. Box 17, 3300 AA Dordrecht, The Netherlands.
www. springer, com
Printed on acid-free paper
All Rights Reserved
© 2007 Springer
No part of this work may be reproduced, stored in a retrieval system, or transmitted
in any form or by any means, electronic, mechanical, photocopying, microfilming, recording
or otherwise, without written permission from the Publisher, with the exception
of any material supplied specifically for the purpose of being entered
and executed on a computer system, for exclusive use by the purchaser of the work.
Contents
Foreword ix
Preface xiii
Acknowledgments xvii
1
Microcontrollers: Yesterday, Today, and Tomorrow 1
1.1 Denning Microcontrollers 1
1.2 Eagle's View: Microcontrollers and Other Competing Devices 2
1.3 Vignettes: Microcontrollers 3
1.4 Microcontroller Applications 5
1.5 Growth Economics 7
1.6 The Major Players in the Microcontroller Chip Market 8
1.7 Architectural Trends 10
1.8 Jump Starting Your First Embedded System Project 14
1.9 Execution of Embedded System Project: Is it a
Gordian's Knot? 16
2
Integrated Development Environment 19
2.1 Getting Familiar with the IDE 19
2.2 Working with Keil IDE 20
2.3 Development Flow for the Keil IDE 21
3
Art of C Programming for Microcontrollers 29
3.1 Familiarizing with Your Compiler Capabilities 29
3.2 Whether to Use Headers or Not? 30
3.3 Basic C Program Structure 34
3.4 Differences from ANSI C 34
vi Contents
Exploring the Capabilities of On-Chip Resources Programming 37
for I/O Ports, Interrupts and Timer/Counter
4.1 Importance of Ports 37
4.2 Simple Ideas for Port Expansion 46
4.3 LED Interfacing 46
4.4 Relevance of LEDs in Today's Lightening Industry 48
4.5 Different Programs for LED Interfacing 48
4.6 More Projects on LED Interfacing to Microcontrollers 51
4.6.1 Running LEDs 51
4.6.2 Running Bicolor LED 51
4.6.3 Interfacing 6 LEDs
Using 3 Microcontroller Pins by 51
4.6.4 The LED Dimmer Demoboard 51
4.6.5 Fading RGB LED 52
4.6.6 LED Moving Font 52
4.7 DIP Switch Interfacing: Getting Input to Your
Embedded System 52
4.8 LCD Interfacing 54
4.9 Interrupts in Microcontrollers 57
4.9.1 Writing ISRs in C 58
4.9.2 A Word about Interrupt Latency 63
5
Hyperterminal-Based Control 69
5.1 Hyperterminal 69
5.2 Packet-based Control Scheme 69
5.3 Mechanism and Lots of Possibilities 70
5.4 Application 1: Packet-based Interface for LEDs 71
5.5 Application 2: Packet-based Interface for Stepper
Motor Control 74
5.6 Application 3: Home Automation from PC HyperTerminal 78
6
Embedding Microcontroller in Routine Applications 85
6.1 Application 1: Podium Timer 85
6.2 Application 2: Front Desk Notifier 90
6.3 Application 3: Cafeteria Food Alert/Microcontroller-based
Menu Card 94
6.4 Application 4: Chimney Sentinel 100
6.5 Application 5: Who's First Timer 104
Contents vii
6.6 Application 6: Counting Cars 110
6.7 Application 7: Anonymous Voting 114
6.8 Energy Efficient Lighting Using Microcontroller 119
7
Microcontroller-based Measurement and Control Applications 123
7.1 Application 1: Reading a PWM Waveform Using
Microcontroller 123
7.2 Single Set-point On/Off Controller 127
7.3 Application 3: I 2 C Interface with Serial EPROM 133
8
Securing Your Embedded System Application 139
8.1 Security Challenges in Embedded Systems 139
8.2 Application 1: Authentication for Your Embedded
System Application 140
8.3 Application 2: Timeout Waiting for Input Data 144
References 151
Index 155
Foreword
If we accept the premise that an embedded engineer is made rather
than born, then how does one go about making a good one? The authors
of this book Exploring C for Microcontrollers: A Hands-on Approach are
certainly "good ones" . Not only do they explore some of the influences
that shaped themselves but they also try to shape "would-be" embedded
engineers. Research and developmental activities in embedded systems
has grown in a significant proportion in the recent past. Embedded soft-
ware design is not new to the world, but with the changing time, it
has gained considerable momentum in the recent past, and many young
engineers are strongly inclined to pursue their future in this field. The
book is mainly targeted to these engineers who would like to understand
in great depth the synergetic combination of hardware and software.
The book is divided into eight chapters. Chapter 1 introduces a brief
background about micro-controllers and explains how they are embed-
ded into products commercially available in the market to emphasize the
importance of these in the daily life of mankind. It also gives an insight
into the architectural details and embedded system concepts for stu-
dents' projects to motivate them into this exciting field. The rest of the
book concentrates on software development. The integrated development
environment (IDE) is introduced in Chapter 2. Again the screen shots
and step-by-step procedure will certainly make the students and engi-
neers fully understand the development process. Chapter 3 differenti-
ates the embedded C paradigm from the conventional ANSI C. Again
the authors explain how to successfully overcome the memory and time
constraints while developing an embedded C program. Chapter 4 gives
an overview of program development for on-chip resources for MCS51
family of microcontrollers. Chapters 5-8 are devoted to live case studies.
The book has come out with an elegant presentation to aspiring
students and engineers from the teaching experience and technical
knowledge the authors have put over a long time in this field. I strongly
recommend this book for intermediate programmers, electronics, electri-
cal, instrumentation engineers or any individual who is strongly inclined
IX
x Foreword
to take up his or her career in embedded C programming. I am sure the
reader will experience learning embedded programming by example and
learning by doing. Last but not the least, this book will certainly be a
value addition to the world of embedded programming.
Dr. A. Senthil Kumar
Head
Data Quality Evaluation
National Remote Sensing Agency
Department of Space
Government of India
Dr. Senthil Kumar is Head of DQE and PQCD sections of National
Remote Sensing Agency (NRSA) an autonomous operational center
under Department of Space (DOS), Government of India. This is the
nodal agency in the country for receiving, processing, and distributing
the satellite and aerial remote sensing data and products. NRSA is also
responsible for providing end-to-end solutions for utilization of data
for geospatial applications and information services. NRSA has a huge
archive of remote sensing data acquired through Indian and foreign
satellites and also has the capability to acquire data pertaining to any
part of the globe on demand. It is one of the important centers for
promotion of remote sensing and geographic information system tech-
nologies in India. NRSA has set up satellite data processing facilities
starting from data reception to utilization at various centers within
India and across the globe.
Preface
The past few decades have witnessed evolution of microcontrollers.
They have revitalized a number of products or equipment in almost all
fields including telecommunications, medical, industrial, and consumer
products. These embedded microcontroller systems now resides at the
heart of modern life with a variety of applications in fields like con-
sumer electronics, automotive systems, domestic, and even in aerospace
products. Embedding a microcontroller in an electronics instrument or
product requires a specialized design skill which requires a synergy of
hardware and software skills.
In our day-to-day life we come across a number of embedded products.
When we switch on the washing machine or send an SMS on a cell phone
one cannot prevent without thinking the mechanism and the co-working
of hardware and software in the background. The market for such smart
embedded products is occupying newer and newer applications seem-
ingly impossible few years back. Last year the IDC, a premier global
market intelligence firm, revealed that the embedded industry product
development was expected to be as high as $75 billion. This entails the
industry requirement of trained human resource with mixed skill set
both in hardware and software. Unfortunately the synergetic demand
of hardware and software or sometimes even referred to as firmware
competency has led to a supply-demand gap of HR in this field. This
gap expressed in numerical figures led to requirement of around 150,000
embedded engineers to serve the global embedded industry. This book
is ideal for all those who would like to pursue their career in the exciting
world of microcontroller-based embedded systems. The approach is ped-
agogical; first the hardware module is presented and then the associated
software code in Keil C.
The hardware designed is useful for engineering graduates and prac-
ticing professionals with the required knowledge and practical hands on
skills to design with embedded systems. However, the prerequisite for
the book is background of theoretical aspects of architecture of micro-
controllers especially the MCS-51 family. The book starts with initial
XI
xii Preface
experiments, which provide familiarization with the capabilities and the
limitations of the basic 8051 microcontroller using a simulator. Once the
reader is comfortable with these primitive programs which covers almost
all the on-chip resources, he or she can switch to more advanced ones.
The Scope of the Book
We now review the topics covered in sequence, chapter by chapter.
Chapter 1 provides an overview of microcontrollers and their appli-
cations in different domains. The architectural trends and the growth
economics emphasizes the importance of the subject. The photograph of
the setup and the hints toward project execution will definitely boost the
confidence of the novice to kick-start the project with minimal resources.
Chapter 2 is devoted to the IDE for the MCS-51 family. The simulation
and single stepping as described in this chapter will solve all the project
intricacies of the readers. Chapter 3 illustrates the basic difference in
traditional C programming and embedded C. Chapter 4 deals with the
programming of on-chip resources of MCS-51 family microcontrollers
in C. The theoretical details of these on-chip resources such as ports,
timers, etc., are completely eliminated. As the book aims at hands-on
approach, the programs for the on-chip resources have been developed
and their execution is illustrated in the Keil simulation environment.
The last four chapters, i.e., 5-8 deal with various project case stud-
ies. Several case studies in various application domains such as lighting,
measurement and control, security, and domestic applications are devel-
oped from scratch. The hardware and software developed in the form of
case studies also caters to a set of mini projects, which are discussed in
detail from the design phase to the actual implementation on a target
system. There are 17 case studies given in this book on various systems
that you may encounter in day-to-day life. Overall the hardware and
software developed in this book can be reused for any embedded sys-
tem project and is expected to act as a rapid prototyping unit for the
embedded systems industry.
Reasons for Proposing this Book
The market is flooded with a number of good books on embedded sys-
tems designed especially with the most popular MCS-51 family. These
books are traditional in nature, i.e., they start with the routine archi-
tectural features of 8051, description of registers, ports, interrupts, etc.
Most of these are already covered in the device data sheet and appli-
cation notes. In the present book all such routine features are skipped.
The focus is on programming microcontrollers to be specific MCS-51
Preface xiii
family in 'C using Keil IDE. The book presents 20 live case studies
apart from the many basic programs organized around every on-chip
resource like port, time/counter, interrupt, serial I/O, etc. Rather than
introducing the underpinning theory or reproducing lengthy data sheets,
our approach is "learning-through-doing" and one that appeals to busy
electronics designers. The 'C codes given are well supported by easy-to-
understand comments wherever required. Mastering the basic modules
and hands-on working with the projects will enable the reader to grasp
the basic building blocks for most 8051 programs. Whether you are a
student using the MCS-51 family of microcontrollers for your project
work or an embedded systems programmer, this book will give you a
kick start in using and understanding the most popular microcontroller.
Authors through their interaction with the undergraduate and post-
graduate students as well as industry professionals have found that such
a book is the need of the microcontroller community interested in C
programming. The book will bridge the gap between the microcontroller
hardware experts and the C programmers.
Major Features
The objective of this book is to introduce the readers to the design
and implementation of an embedded system. It covers the unique require-
ments and limitations of operating in an embedded environment. It also
covers microcontrollers as the most widespread example of embedded
systems. In particular, it focuses on the MCS-51 family of microcon-
trollers, their programming in C language, and interfacing techniques.
Special emphasis is to provide hands-on experience for the readers
using a hardware and interfacing modules described in this book. The
aim is to empower the reader to actually solve his or her problem with
a practical hands-on pedagogy through the hardware and software pre-
sented in this book. The principle of "Design Reuse" is explained effec-
tively.
Further, the readers will also learn how to follow the sequence of data
flow through the microcontroller when a program is executed. Addi-
tionally, the readers will learn the operation of the microcontroller's
I/O functions and the external devices driven by the microcontroller.
Hardware and software design issues are discussed for specific systems
implemented using MCS-51 as the embedded microcontroller.
Acknowledgments
We would like to take the opportunity to thank all those who have
contributed or helped in some way in the preparation of this text.
Particular thanks must go to our heads of the institutions - - Professor
M.M. Salunkhe, Vice Chancellor, Shivaji University, Kolhapur, India,
and Professor P.S. Zacharias, Vice Chancellor, Goa University, Goa,
India for the encouragement and support. We would also like to
thank Mr. P. Venugopal, Director, Software Technology Parks of India,
Maharashtra Region, for his support. Dr. Kamat and Dr. Naik would
like to thank their respective wives for their understanding and patience
shown when the preparation of the book took time which could have
been spent with the family. Our thanks then to Kamat's wife Rucha
and Naik's wife Deepa.
Additionally, Mr. Shelake and Mr. Parab would like to express grati-
tude to their parents for their encouragement and support over the years.
Kamat would like to dedicate his contribution to this book to the mem-
ory of the late Professor G.G. Tengshe and the late Dr. V. Rao Indolkar,
ACD Machine Control Tools Ltd., Mumbai.
Dr. Kamat would also like to thank to his teacher in this field
Mr. S. Ramgopal, Indian Institute of Science, Bangalore, and Dr. Senthil
Kumar, Dr. Raghurama, Deputy Director (Academic) of BITS Pilani
as well as Mr. K.S. Deorukhkar for help in reviewing and critical sug-
gestions. The past batches of M.Sc. Electronics students of both Shivaji
University and Goa University especially Mr. Roy, Mr. Rupesh from
Satyam Computers must be thanked for generation of problems for
programs developed in this book.
■ Jivan S. Parab
■ Vinod G. Shelake
■ Dr. Rajanish K. Kamat
■ Dr. Gourish M. Naik
xv
Chapter 1
Microcontrollers: Yesterday, Today,
and Tomorrow
1.1 Defining Microcontrollers
It is said that from the definition everything true about the con-
cept follows. Therefore, at the outset let us take a brief review of how
the all-pervasive microcontroller has been defined by various technical
sources.
A microcontroller (or MCU) is a computer-on-a-chip used to con-
trol electronic devices. It is a type of microprocessor emphasizing
self-sufficiency and cost-effectiveness, in contrast to a general-purpose
microprocessor (the kind used in a PC). A typical microcontroller con-
tains all the memory and interfaces needed for a simple application,
whereas a general purpose microprocessor requires additional chips to
provide these functions (Wikipedia [1])
A highly integrated chip that contains all the components compris-
ing a controller. Typically this includes a CPU, RAM, some form of
ROM, I/O ports, and timers. Unlike a general-purpose computer, which
also includes all of these components, a microcontroller is designed for
a very specific task to control a particular system. As a result, the
parts can be simplified and reduced, which cuts down on production
costs. . . . (Webopedia [2])
A {microprocessor} on a single {integrated circuit} intended to ope-
rate as an {embedded} system. As well as a {CPU}, a microcontroller
typically includes small amounts of {RAM} and {PROM} and timers
and I/O ports. . . .(Define That [3])
A single chip that contains the processor (the CPU), non- volatile
memory for the program (ROM or flash), volatile memory for input and
output (RAM), a clock and an I/O control unit. . . . (PC Magazine [4])
A microprocessor on a single integrated circuit intended to operate
as an embedded system. As well as a CPU, a microcontroller typically
includes small amounts of RAM and PROM and timers and I/O ports.
...(FOLDOC [5])
1
J.S. Parab et al. (eds.), Exploring C for Microcontrollers, 1-18.
© 2007 Springer.
2 Eagle's View: Microcontrollers and Other Competing Devices
The definitions given by various sources describe microcontroller as
an integrated circuit (IC) with processor as well as peripherals on chip.
But the crux of the matter is the widespread uses of microcontrollers
in electronic systems. They are hidden inside a surprising number of
products such as microwave oven, TV, VCR, digital camera, cell phone,
Camcorders, cars, printers, keyboards, to name a few.
The last three decades and especially the past few years have wit-
nessed the tremendous growth in the top-of-the-line processors used
for personal computing and digital signal processor (DSP) applications.
Today, the use of microcontrollers in embedded systems outnumbers
the use of processors in both the PC and the workstation market. It is
estimated that over 50% of the vast majority of the computer chips sold
are microcontrollers. The main reasons behind their huge success are
powerful yet cleverly chosen customizable electronics, ease in program-
ming, and low cost. These days microcontrollers find increasing appli-
cation even in areas where they could not be used previously. With the
decreasing costs and footprints, it is now possible to have small-sized
and cost-effective microcontroller units (MCUs) for new applications.
The microcontrollers today are small enough to penetrate into the tra-
ditional market for 4-bit applications like TV remote controls, toys, and
games. For the simplest of all control applications they can offer high
value smart switch functionality for applications that previously used
electromechanical devices. Also the customers now can add intelligence
to their end products for low cost as per the microcontroller market
report by Frost & Sullivan research service [6].
1.2 Eagle's View: Microcontrollers
and Other Competing Devices
Generally the technical fraternity try to compare the various devices
like microprocessors, PCs, microcontrollers, DSPs, and reconfigurable
devices like FPGAs and CPLDs. An interesting point to note is that
embedded systems are made using all the above-mentioned devices
except PC owing to its general purpose architecture. As programma-
bility is the common feature of all these devices, they have their firm
footing in different application domains. On one side of the spectrum,
microcontroller-based embedded system design emphasizes on task-
specific dedicated applications at low power, low cost, high through-
put, and highest reliability. On the other extreme of the spectrum,
FPGA-based embedded systems dominate their custom computing
architectures. Unlike microcontrollers, these systems can be reconfigured
on the fly to suit the application with higher computational density and
Microcontrollers: Yesterday, Today, and Tomorrow 3
throughput. With the proliferation of density, FPGA-based embedded
systems offer higher performance with the only challenging issue of
memory required to store their configurations.
The technical community also tends to associate various character-
istics of embedded systems with microprocessors and microcontrollers.
The microprocessors are typically found to dominate the desktop arena
focusing on more and more bit processing capability, with other fea-
tures such as fairly good amount of cache with memory management
and protection schemes supported by the operating system. Although
microcontrollers share flexibility aspect of microprocessors through pro-
gramming, 8-bit versions are more in use (although 16- and 32-bit exist)
with RAM and ROM (instead of cache) added with many on chip
peripherals like timer/counter, decoder, communication interface, etc.
In the literature many embedded systems products have been reported as
microprocessors. On the other side of the processor spectrum, a DSP pos-
sesses special architecture that provides ultra- fast instruction sequences,
such as shift and add, multiply and add, which are commonly used in
math-intensive signal processing applications. The common attributes
associated with the DSPs are multiply-accumulate (MAC) operations,
deep pipelining, DMA processing, saturation arithmetic, separate pro-
gram and data memories, and floating point capabilities required most
of the time. However, the line of differentiation between all these devices
is getting blurred at a rapid pace. With the introduction of fuzzy logic,
artificial intelligence and networked communication capabilities in the
consumer products like refrigerators, mobile phones, and cars, conver-
gence of the architectures of most of the above-mentioned programmable
devices is witnessed by the industry. Today's ideal microcontroller is
expected to offer plenty of MIPS, run the DSP programs with the same
speed of the DSP processor, integrate all its peripherals and support
flash, communicate with the world with 12 C or CAN protocols, with-
stand extremes of environment in a car engine, and cost but a few
cents.
1.3 Vignettes: Microcontrollers
It is interesting to note that the development of microprocessors seems
to be an accident out of the microcontroller synthesis. In 1969, Busicom,
a Japanese company, approached Intel to convert their special pur-
pose ROM and shift register-based calculator cores into a specialized
application specific processor. The objective was the development of
microcontrollers rather than a general purpose of CPU chips for key-
board scanning, display control, printer control, and other functions for
4 Vignettes: Microcontrollers
a Busicom-manufactured calculator. However, the Intel engineers opted
for a more flexible programmable microcomputer approach rather than
the random logic chip-set originally envisioned by Busicom. The four
designs [7] proposed by Federico Faggin, Ted Hoff, and Stan Mazor from
Intel were a 2048-bit ROM with a 4-bit programmable input /output
port (4001); a 4-registers x 20-locations x 4-bit RAM data memory
with a 4-bit output port (4002); an input/output (I/O) expansion chip,
consisting of a static shift register with serial input and serial/parallel
output (4003); and the 4-bit CPU chip (4004). The 4001, 4002, and
4003 are very close to microcontroller kind of architecture rather than
microprocessor. However, the Intel 4004, which was supposed to be the
brains of a calculator, turned out to be a general-purpose microproces-
sor as powerful as ENIAC. The scientific papers and literature published
around 1971 reveal that the MP944 digital processor used for the F-14
Tomcat aircraft of the US Navy qualifies as the "first microprocessor" .
Although interesting, it was not a single-chip processor, and was not
general purpose -- it was more like a set of parallel building blocks you
could use to make a special purpose DSP form [8]. It indicates that
today's industry theme of converging DSP- microcontroller architectures
was started in 1971.
The other companies were also catching up at the same time. The
first official claim of filing the patent goes to Texas Instruments under
the trade name TMS1000 way back in 1974. This was the first micro-
controller which included a 4-bit accumulator, 4-bit Y register and 2- or
3-bit X register, which combined to create a 6- or 7-bit index register
for the 64 or 128 nibbles of on-chip RAM. A 1-bit status register was used
for various purposes in different contexts. This microcontroller served as
the brain of the Texas Instrument's educational toy named "Spark and
Spell" shown in the movie ET: The Extraterrestrial. In 1976, Intel intro-
duced the first 8-bit microcontroller family MCS-48 which was so pop-
ular that they could ship 251,000 units in that year. After four years of
continuous research, the MCS-48 family was upgraded to 8051, an 8-bit
microcontroller with on-board EPROM memory. Intel shipped 22 million
pieces in 1980. The market requirement was so much that the total units
sold in three years later were 91 million. The year 2005 is a special one
for the microcontroller 8051. It has celebrated its 25th anniversary. But,
also in 2005, Intel notified they would discontinue all automotive versions
of their microcontrollers, including 8051. Car engine control units were
once perhaps the most prominent application for 8051s. This means only
one thing, Intel gives up the microcontrollers for good. This is confirmed
by product change notification published in early 2006, announcing that
Intel drops its whole microcontroller business [9].
Microcontrollers: Yesterday, Today, and Tomorrow 5
1.4 Microcontroller Applications
The microcontroller applications are mainly categorized into the
following types (see Figure 1.1):
Audio
Automotive
Communication/wired
Computers and peripherals
Consumer
Industrial
Imaging and video
Medical
Military/ aerospace
Mobile/wireless
Motor control
Security
General Purpose
Miscellaneous
Automobile industry is the main driving force in propelling the growth
of microcontrollers. It is estimated that the microcontrollers constitute
33% of the semiconductors used in a vehicle [10]. Requirements of the
automobile sector has forced the microcontroller manufacturers to come
out with the new bus protocols such as control area network (CAN)
and local interconnect network (LIN). Microcontrollers of all bit cores
are used in vehicles according to the Frost & Sullivan Industry report.
The 8- and 16-bit microcontrollers are used for low-end applications
and lower-cost vehicles while the 32-bit microcontrollers are used for
high-end application and high-end vehicles. It is estimated that cur-
rently 30-40 microcontrollers are used in low-end vehicles and about
70 microcontrollers are used in high-end vehicles. These requirements
are continuously increasing and it is highly likely that the count of micro-
controllers in vehicles will further increase in the future, quotes World
Microcontrollers Market Report by Frost & Sullivan [10].
6
Microcontroller Applications
Figure 1.1 Microcontroller application tree
Microcontrollers: Yesterday, Today, and Tomorrow 7
Embedding microcontrollers in the product offers some unique
advantages. For an example, in the latest technology washing machines,
a transmission is no longer required because a lower-cost AC induction
or reluctance motor controlled by sophisticated microcontroller-based
electronics can provide all the normal machine cycles [11]. Additionally,
the electronically controlled induction or reluctance motor provides a
more effective and gentler agitation (wash) cycle that allows the drum
containing the clothes to be rotated first in one direction, then stopped,
and rotated in the opposite direction without requiring any additional
mechanical device. This forward/reverse agitation cycle provides a more
effective means of cleaning your clothes without damaging the fibers
used to make them.
It is also observed that the induction of microcontrollers in a product
has increased the market demand of the product itself. One such exam-
ple is NEC Electronics' 8-bit microcontroller [12], which is employed in
over half of the digital cameras produced throughout the world, thus
making it a hit product - albeit one that plays its role behind the scenes.
In 2003, the shipment volume of 8-bit microcontrollers for digital cam-
era use achieved monthly shipments of two million. Currently, the most
commonly used microcontroller for digital cameras is the |lPD78003x.
The industry's top-level, low-voltage (1.8 V) A/D converter is built
into this compact 64-pin QFP package with an edge measuring a mere
10 x 10 mm.
1.5 Growth Economics
Many industry analysts have reported a bright growth economics
for microcontroller in the near future. Bourne Research reports that
MEMS-based motion, pressure, and acoustic sensors (as well as other
next-generation sensing technologies) are not only finding their way into
classic consumer products like toys, housewares, sporting goods, and
clothing, but applications as far-reaching as flooring materials, medical
diagnostics, retail fixtures, and vending machines. System complexity is
just as varied, but Bourne Research notes that, more often than not,
these products will utilize multiple sensors and microcontrollers [13].
Another interesting report by the Semiconductor Industry Association
(SI A) reveals that the microcontroller sales are projected to grow by
1.9% to $12.3 billion in 2006 and to $15.4 billion in 2009, a compound an-
nual growth rate (CAGR) of 6.3% [14]. The positive growth economics of
microcontroller chips also ushers the associated growth of software such
as simulators, cross compilers, and assemblers. The market is witnessing
many novel supporting software packages with simple user interface with
convenient compiling and debugging tools.
8
Microcontroller Applications
1.6
The Major Players in the Microcontroller
Chip Market
Table 1.1 Major players in the microcontroller market. (From 2006 EDN Directory
of Microprocessors and Microcontrollers)
Name
of the
company
Product range
Application domain
Actel
Altera
Altium
Analog
devices
Applied
Micro
Circuits
Corp
ARC Inter-
national
ARM
Atmel
Core8051
8-bit-microcontroller IP
Nios Il/f (fast), Nios Il/e
(economy), Nios II/s
(standard), Soft IP cores
Royalty- free, 8- and 32-bit,
FPGA-based soft processors,
and FPGA-independent
TSK3000RISC core
ADuC7128 family of precision
analog microcontrollers;
ADSP-BF561 Blackfin
ADSP-BF534 Blackfin, BF539
with CAN
Embedded PowerPC proces-
sors PPC405CR PPC405EP,
PPC405EZ, PPC405GP,
PPC405GPr, nP405H, etc.
Two configurable, 32-bit
processor-core families
ARC600 and ARC700
Range of processor cores,
including the ARM7, ARM9,
ARM10, and ARM11 families
and the new Cortex family
featuring Thumb- 2 technology
AVR, AVR32, ARM7, ARM9,
8051, Teak, and Diopsis DSP
cores
Consumer, communications, auto-
motive, industrial, and military/
aerospace applications
Automotive, consumer, industrial,
medical
Automotive, industrial,
communications, and
computer-peripheral
Audio, automotive,
communication/wired, consumer,
industrial, imaging and video,
medical, motor control, security
Communication/wired, computers
and peripherals, consumer,
industrial, imaging and video,
medical, mobile/wireless, motor
control, security
Sound advanced subsystems
targeting portable media devices
and advanced-definition audio
applications
Audio, automotive,
communication/wired, computers
and peripherals, consumer,
industrial, imaging and video,
medical mobile/ wireless, security
Consumer, computer/networking,
communications, security/smart
cards, automotive, industrial,
medical, military, and aerospace
applications
Microcontrollers: Yesterday, Today, and Tomorrow
9
Cast
Cirrus Logic
Dallas Semi-
conductor
Freescale
Semicon-
ductor
Lattice
Semicon-
ductor
Luminary
Micro
Microchip
Technology
8-, 16-, and 32-bit IP cores
including 8051 cores with
instruction execution one clock
per cycle; configurable 8051,
8-bit Z80 and 16-bit 68000
compatible devices
ARM9- and ARM7-based
embedded processors
EP9301, EP9302, EP9307, etc.
Four microcontroller families
targeting networked, secure,
mixed-signal, and 8051 drop-in
designs
Ultralow-end, RS08-based,
8-bit microcontrollers to an
advanced 32-bit ColdFire core
Fujitsu
32, 16, and 8-bit
Micro-
microcontrollers with
electronics
onboard-flash, ROM, ADC,
America
DAC, CAN (controller area
network), USB, and LCD
controllers
Infineon
8-, 16-, and 32-bit bit
Technolo-
XC886/888, XC164CM
gies
TC116x
8-bit microcontrollers,
including the 8051 and PIC,
through its partners, Cast and
Digital Core Design,
LatticeMico8 an 8-bit soft
microcontroller core
ARM Cortex-M3-based
microcontrollers
8- and 16-bit PIC
microcontrollers, as well as
16-bit dsPIC DSCs (digital
signal controllers)
Automotive, communication/
wired, computers and
peripherals, consumer
industrial, imaging and video,
medical military/aerospace,
mobile/wireless motor control
Audio and industrial markets
Networking applications as
they have an optional TCP/IP
stack in ROM, a built-in
Ethernet MAC (media access
controller), CAN (controller
area network), and parallel
and serial ports
Mobile and videoconferencing
phones, portable media
players, PDAs, and portable
GPS applications, networking,
home and SOHO
(small-office/home-office)
networking, automobile
Automotive, communications,
computer peripheral,
industrial, and consumer
applications
Industrial and automotive,
industrial motor control,
building control for lifts and
escalators, intelligent sensors,
distributed I/O modules, and
industrial automation
Automotive,
communication/wired,
computers and peripherals,
consumer industrial, medical
Industrial and motor control
Motor control and general
purpose
10
Architectural Trends
Table 1.1 Continued.
Name
of the
company
Product range
Application domain
National
Semicon-
ductor
NEC
Electronics
America
COP8 flash microcontrollers
featuring an 8-bit core with 32
kbytes of onboard flash
8-bit uPD78F0711 and
uPD78F0712 flash-based
microcontrollers, 32-bit
flash-based V850ES/IE2 series
Hardware communications
peripherals, and an
expandable external bus to
target embedded system
communications applications,
such as automotive telematics,
vehicle-network gateways,
hands- free car kits, and
industrial and medical
instrumentation and control
Consumer appliances, home
health care, building
management systems and
industrial controlled
applications
1.7
Architectural Trends
The emerging trends in microcontroller architecture are dictated by
the technological needs of the embedded system applications. In gen-
eral the common road map is characterized by the features like single
functional, tightly constrained in terms of cost, power, speed, and foot-
print as well as continuously reactive in a real-time manner. The micro-
controller world is divided over the architecture used. Controllers like
8051, 68HC11 join their microprocessor counterparts (80 x 86 family) in
using Von-Neumann architecture by sharing RAM and program mem-
ory with the same bus. This imposes the same bit width for the buses
irrespective of their requirement, which is not the case with the PIC
processors which uses Harvard architecture.
8-bit Treads on MCU Turf
It is really interesting to note that in this era of 32-bit processors,
the 8-bit microcontrollers are flourishing and enjoying a stable future.
The reasons behind this are low cost and inexpensive development soft-
ware. An 8-bit microcontroller like 8051 today enjoys 40% of the market
share [15]. It has become so popular that about 40 manufacturers now
make it with 800 derivatives used for diverse applications right from
Microcontrollers: Yesterday, Today, and Tomorrow 11
simple process control to high-tech telecom. The original MCS-51 family
developed by Intel consists of CHMOS processors with features such
as 8-bit CPU optimized for event control, Boolean processing, on-chip
memory (up to 32 K) and on-chip peripherals (timer/counters, serial
ports, PC A, etc.). The other manufacturers like Atmel, Dallas, Philips,
Analog Devices, etc., have extensively worked for strengthening the basic
core by introducing additional features such as Additional Data Pointers
(DPTR), Extended Stack Space, Fast Math Operations and Extended
or Reduced Instruction Sets to name a few. Table 1.1 summarizes the
features of the popular 8051 derivatives manufactured by various compa-
nies. Although industry analysts predicted the saturation of 8051 family
and also its death, it turned out to be a rumor. In 2003, Cygnal released
world's highest performance 8051 microcontroller [16]. The C8051F120
family devices include 128 Kbyte Flash memory, 8448 byte RAM, and
are packaged in either a 100-pin or 64-pin TQFP. On-chip peripherals
include a 12-bit lOOksps ADC, two 12-bit DACs, a 2% internal oscillator,
temperature sensor, voltage reference, two UARTs, and many features
of a DSP processor.
Low Power Design
The latest 8-bit devices continue to drive up the performance bar
with simplicity for usage and ease of programming. Most of these de-
vices are aimed at low power consumption achieved by using sleep modes
and the ability to turn certain peripherals on and off. The best example
for this is XE88LC02 from XEMICS [17], a recently launched microcon-
troller, which features programmable gain/offset amplifier followed by
high resolution ADC with four differential or seven pseudo differential
inputs, with current consumption as low as 2 |iA in real-time clock mode
and a typical 300|iA/MIPS in sustained computing mode. Recently,
Atmel has also strategically evolved their microcontroller architecture by
implementing novel power saving techniques. Atmel' s picoPower tech-
nology uses a variety of techniques that eliminate unnecessary power
consumption in power-down modes. These include an ultra- low-power
32 kHz crystal oscillator, automatic disabling and re-enabling of brown-
out detection (BOD) circuitry during sleep modes, a power reduction
register that completely powers down individual peripherals, and dig-
ital input disable registers that reduces the leakage current on digi-
tal inputs [18]. PicoPower microcontrollers consume down to 340 Jl A in
active mode, 150 |iA in idle mode at 1 MHz, 650 nA in power-save mode
and 100 nA in power-down mode.
12 Architectural Trends
Convergence of DSP with Micro
The trend of convergence of functionality in microcontroller was
started in the 1970s with MP944, which had more of DSP orienta-
tion. For a microcontroller engineer to consider a DSP or for a DSP
engineer to use a microcontroller, three strict criteria must be met:
price/performance, peripheral set, and development tool quality [19].
This trend is now more pronounced as seen in the newly launched
microcontroller cores by Motorola. For instance, in its 56F83xx family
of microcontrollers, Motorola has introduced a series of devices that it
intends to meet uprated processing needs in today's systems - partic-
ularly in automotive systems while keeping 8/16-bit economics and
avoiding the shift to 32-bit controllers. The defining features of the
device series are the inclusion of some DSP attributes and the use of
on-chip flash memory instead of EEPROM. The term "hybrid" describes
the devices' combination of microcontroller and DSP functions. These
devices are not hybrid in the sense that they combine twin processing
cores; rather, they add the facility to efficiently execute certain DSP-
like arithmetic functions such as multiply-accumulate operations [20].
These kinds of architectures are in heavy demand owing to such hybrid
signal processing requirements in application domains such as speech
processing in consumer applications. The key challenges in converging
these two diversified architectures are combining the pipelining, register
oriented, complex conditional resolving architecture of microcontrollers
with the multiply-accumulate, data massive, and deterministic software
typically with zero overhead loops of the DSPs. With the inclusion of
DSP functionality in microcontrollers many things such as modem sup-
port, compression of data voice, and image as well as filtering and speech
synthesis/recognition are possible. This has been successfully done in
some of the recently launched microcontrollers like Goal Semiconduc-
tor's VMX1016. This microcontroller possesses a powerful hardware
arithmetic unit with 32-bit barrel shifter that can perform simultaneous
16-bit signed multiplication and 32-bit addition. Another example of
this convergence is Hitachi's SH3-DSP based on a single instruction
stream approach combining general purpose CPU and dedicated DSP
functionality in a single architecture [21]. These types of microcon-
trollers facilitate upgradation of the embedded systems merely with the
addition of software utilities.
Hidden Debugger
With the increasing design complexity debugging or verification has
become the major bottleneck to meet the tight time to market schedule.
Microcontrollers: Yesterday, Today, and Tomorrow 13
It is estimated that debugging time is almost 30-50% of the total deve-
lopment time. The conventional techniques such as extra design for
testability by embedding test points or scan chains as well as exter-
nal debugger are on the way of extinction. The new microcontrollers
are struggling to sort out the resource requirement vs computational
complexity dilemma. The use of logic analyzer for monitoring the clock
quality as well as the bus activity has become very expensive and many
times physically impossible with the shrinking footprint of microcon-
trollers operating at the clock speed as high as 100 Mhz. The IEEE-ISTO
Nexus 5001 Forum which comprises around 25 major microcontroller
manufacturers defines a common set of on-chip debug features, proto-
cols, pins, and interfaces to external tools which may be used by real-time
embedded application developers. As a result, more than 70% of leading
embedded microcontroller vendors now have dedicated circuits and pins,
whichassist in new product development based on the IEEE 1149.1 Joint
Test Action Group (JTAG) 4- wire serial interface [22]. Apart from the
JTAG interface, today's microcontrollers are enriched with the back-
ground debug mode (BDM) and on-chip emulation being achieved at
higher abstraction level for reducing size and searching space in the
debugging. Although the microcontroller community is still far from
implementing the debugging solution for pointer problems, accessing
unintialized memory, and interprocess interaction, the chips are domi-
nated with single stepping and breakpoint utilities, e.g., the recently
launched C8051F120 [23] has on-chip debug circuitry facilitating full-
speed in-system debug features such as single-stepping, breakpoints, and
modifying registers and memory.
Web-Enabled Microcontrollers
Embedded internetworking allows anytime, anywhere, control of the
product with a regular self-maintenance and pervasive, wearable com-
puting. The tangible benefits of Internet connectivity in products like
air conditioner or washing machine are self-upgradation by downloading
the software updates, lowering cost by fine-tuning energy consumption
in peak hours, generating auto maintenance alarms, etc. Microcontroller
manufacturers have come out with new processors having a built-in
capability to cope with the challenges of web processing. Dallas Semi-
conductor has come out with the microcontrollers that can directly serve
up web pages. TINI (Tiny InterNet Interface) [24] is a microcontroller-
based development platform that executes code for embedded web
servers. Remote devices can have preferences and settings adjusted from
afar, just by having their administrator browse a web page hosted by
14 Jump Starting Your First Embedded System Project
the microcontroller no other computers required. The TINI development
platform combines a powerful chipset and a Java runtime environment
that exposes the extensive I/O capability of the Dallas microcontrollers.
A Java programmer accesses the I/O from robust APIs (Application
Program Interfaces) that include Ethernet, RS-232 serial, I2C, 1-Wire
net, CAN, and memory-mapped parallel bus. By using these APIs,
programmers code functions without worrying about the underlying
interface to hardware peripherals. The runtime environment is tightly
coded for optimized network communications and efficient device I/O
throughput.
Dominance of Soft IP cores/Free Microcontroller?
The new VLSI devices such as FPGAs offer several advantages
over microcontrollers. FPGA-based platform enables the developer to
test (thanks to the JTAG philosophy) and add features in parallel
without the need for repeating the complete testing of the platform
once again. Increasing number of manufacturers are now offering the
FPGA-based microcontroller core. The list of FPGA-based soft IP cores
for 8051-based microcontrollers is available at the web page of Keil
(http://www.keil.com/dd/ipcores.asp). For example, the C-8051 core is
the HDL model of the Intel 8-bit 8051 microcontroller by Aldec Inc. [25].
The model is fully compatible with the Intel 8051 standard and is avail-
able in both EDIF and VHDL netlists formats. The EDIF netlist is used
for the place and route process and VHDL is the post-synthesis netlist
used for the simulation only. Both netlists are technology-dependent
because they are created after the synthesis where the customer needs
to specify a vendor, target family, etc. Even the source code of a set of
HDL testbenches for the cores is also available.
1.8 Jump Starting Your First Embedded
System Project
Figure 1.2 shows a minimum setup required to build microcontroller-
based embedded system project. The foremost requirement is a low-
end PC pre-loaded with the IDE to facilitate the code development,
simulation and testing before actual dumping the code in the flash of the
microcontroller. The Keil IDE is covered in depth in Chapter 2. Most of
the projects developed in this book have been tested on AT89S52 which
has the following features:
■ 8K Bytes of In-System Reprogrammable Flash Memory
■ Fully Static Operation: Hz to 33 MHz
Microcontrollers: Yesterday, Today, and Tomorrow
15
Figure 1.2 Minimum setup recommended for your Embedded System Laboratory
Three-level Program Memory Lock
256 x 8-bit Internal RAM
32 Programmable I/O Lines
Three 16-bit Timer/Counters
Eight Interrupt Sources
Programmable Serial Channel
Low-power Idle and Power-down Modes
4.0V to 5.5V Operating Range
Full Duplex UART Serial Channel
Interrupt Recovery from Power-down Mode
Watchdog Timer
16 Execution of Embedded System Project: Is it a Gordian's Knot?
■ Dual Data Pointer
■ Power-off Flag
■ Fast Programming Time
■ Flexible ISP Programming (Byte and Page Mode)
1.9 Execution of Embedded System Project:
Is it a Gordian's Knot?
Here is a piece of thought for the student community as well as
entrepreneurs looking for a successful embedded system project.
Project Idea to Execution
For successful project development, first you must develop an idea.
There are lots of sources for idea generation. Ideally your ideas should
move from research laboratories towards the marketplace. Many devices
and processes around can be improved by the inculcation of microcon-
trollers. The automation of the nylon rubber stamp making machine
described in the case studies is the best example. The thinking should
ideally go on the following lines: How can the process be controlled
using a microcontroller, ultimate efficiency, or throughput improvement
with embedding of microcontrollers? Are there any simulation tools to
model and estimate before the actual experimentation? In what way
can the process be made more intelligent (or thinking) by using the mi-
crocontrollers? For answering the automation of a process plant using
microcontroller, one must think about the on-chip resources and their
effective usage (e.g., interrupt level/edge, usage of ports, timer/counter,
and so on). The answer to the second question should throw light on
the benefits of using the microcontroller in your project. (Can you think
of green house controller without microcontroller? Or the amount of
energy saved with the microcontroller-based corridor lighting which is
implemented in the case studies.) According to the US Department of
Energy [26], the electricity used to light businesses represents 25% of the
energy they spend; so it is important to develop energy-saving devices.
Even a simple switch equipped with photosensor and microcontroller can
help to reduce lighting energy consumption by 30%.
Simulation is the best methodology to avoid project failure as well
as to work in a time-efficient manner. It is always a good idea to simu-
late the things using the microcontroller IDE instead of rushing to the
project board and actually dumping the code in the on-chip memory.
Microcontrollers: Yesterday, Today, and Tomorrow 17
Moreover, there are simulation tools even to model physical systems
(such as Proteus) which can be used together with the IDE to work out
your project. The last question is little challenging. In order to make
the microcontroller think or make it intelligent you have to resort to
some novel items such as neural net implementation, extrapolation, and
statistical techniques.
As the sole success of the embedded system project is on firmware, the
software and the underlying hardware should not be treated as separate
entities. Therefore, the term "Hardware-Software Co Design" has gained
lots of significance in the field of embedded systems. Following issues
pertaining to hardware and software are of utmost importance while
executing any embedded system project.
Hardware and Software Issues
Even the simplest things dictate the final specifications of the final
product. There is often a major gap between the theory of design and
what "plays" in the real world. The most casual thing for a designer in
any microcontroller-based product is the value of the crystal frequency
which is 11.0592 MHz. The rationale behind this value is the ease of
frequency division to yield exact clock rates for standard baud rate gen-
eration for the UART. However, in the applications where the serial
communication is not at all in picture, the designer has lot of flexibil-
ity in choosing the crystal value. The crystal value decides the execution
speed, e.g., Intel 8051 microcontrollers require a minimum of 12 oscillator
cycles. This means if the crystal is of 12 MHz, then 8051 microcontroller
works at performance of 1 MIPS. If a thorough analysis of the occurrence
of real-time events reveals that this speed is not required, then a designer
may go for a lower value of the crystal. The ultimate advantage is a
significant reduction in power consumption. In CMOS-based versions of
8051, a linear relation between oscillator frequency and power consump-
tion exists. Another lower range crystal value is 7.3728 MHz which can
be used even for standard baud rate generation. The notable thing is:
using counter 1 of 8051; this gives an even 38.4 Kbps rate exactly, which
is not possible even with 11.0952 MHz Xtal. The lower crystal value also
enables to access low-speed peripherals and frees the system from elec-
tromagnetic interference (EMI) evident in high clock speed MCUs.
Problems such as reset, latch-up, memory corruption, and code run-
away are found to fail the embedded system application due to ESD
and EMI. Areas of MCUs typically vulnerable to ESD and EFT stresses
include: power and ground pins, edge sensitive digital inputs, high fre-
quency digital inputs, analog inputs, clock (oscillator) pins, substrate
18 Execution of Embedded System Project: Is it a Gordian's Knot?
injection, general purpose I/O (GPIO) with multiplexed pin functions,
etc. These kind of problems can be solved by using the microcontroller
having proper package style, footprint, and maximum number of supply
and ground pins [27].
While developing the software it is important to have a modular app-
roach. The interrupt service routines should be as short as possible to
reduce the interrupt latency. Readability and debugging specifications
not only enhances the value of the software but also frees the novice
to minimize the learning curve. Choice of the language plays an impor-
tant role to decide the lead time, life and processor migration of your
microcontroller-based product. Using the higher level languages like 'C
for writing programs offers some unique advantages such as faster devel-
opment, improved portability, reusability, platform independence all
at reduced cost. Complex algorithms can be very easily implemented in
'C rather than assembly. As the design evolves in due course, the req-
uired restructuring of the program without breaking the existing design
can be easily done in 'C. Although assembly language is the best choice
for time critical programs, the user face lot of difficulties in managing
large programs especially in memory allocation. "Porting" the assembly
language code to another processor family is almost impossible or very
difficult.
Chapter 2
Integrated Development Environment
Integrated development environment popularly known as IDE is a
suite of software tools that facilitates microcontroller programming. The
Keil IDE enables the embedded professional to develop the program in
C and assembly as well. The IDE passes through the source code to
check the syntax. The compilation leads to a hex file to be dumped in
the microcontroller on-chip ROM. A quick session of simulation and
debugging using the IDE ensures the working of the program before-
hand. The user can verify the results as the package presents screenshots
of on-chip resources. This chapter presents in-depth discussion on using
the \x Vision 2 package of Keil IDE on MS Windows platform. It is
recommended that while going through the discussion the user should
access the (iVision 2 package of the Keil. A step-by-step working as
discussed in this chapter will empower the user to get familiar with
the Keil IDE.
2.1 Getting Familiar with the IDE
The microcontroller product development cycle consists of several
steps such as
■ Development of code either in assembly or C
■ Simulation of the code
■ Dumping the code in microcontroller
■ Prototyping or debugging if required by using in-circuit testing
■ Emulation of the code in case of big project
■ Refining the code, reprogramming and final testing
A microcontroller-based project generally makes several iterations
through the above-mentioned steps before it sees the light of the day.
19
J.S. Parab et al. (eds.), Exploring C for Microcontrollers, 19-28.
© 2007 Springer.
20 Working with Keil IDE
Almost all the microcontroller manufacturers have come out with
the development tools for their products. A suite of such software
tools for microcontroller application development is refereed to as IDE.
Some examples of the popular IDEs apart from Keil are MPLAB from
Microchip, PE micro from Motorola, and AVR studio from Atmel.
Any typical IDE comprises many subcomponents such as a text editor
for entering the code, building tools for converting the code into machine
level, compiler to convert 'C code to assembly or hex format, and linker
to provide absolute addresses to the relocatable object code. The IDE is
generally equipped with powerful code simulator that models operation
of the target microcontroller as code execution is in process. IDEs are
available as a software suite which runs on a stand-alone PC and displays
and allows to modify the contents of virtual I/O and on-chip resources
such as registers. Single-stepping and breakpoint facilities are provided
to systematically execute and watch the cause/effect relationship of the
code. A provision of instruction cycle calculation/display is also provided
so as to see the time/memory efficiency of the code.
2.2 Working with Keil IDE
As the entire software development described in this book is based
on the Keil 8051 Development Tools, it is worthwhile to study the tool
in depth. The Keil IDE is a user-friendly software suite to develop your
'C code and test the same in a virtual 8051 environment. The main
feature of the Keil is that it allows C programmers to adapt to the 8051
environment quickly with little learning curve.
It offers the designer a device database of MCS-51 family from which
the target device of interest can be chosen. The (iVision IDE sets the
compiler, assembler, linker, and memory options for the designer. The
suite comes with numerous example programs to assist the designer to
start his project. With the virtual environment, the available on-chip
resources of the microcontroller chosen can be seen working on the PC
screen. The simulation window facilitates very realistic simulation of
both CPU and embedded peripherals. The graphical window shows the
state and configuration of the embedded peripherals and displays the
interaction of the microcontrollers with external peripherals. Although
the simulation exercise consumes time, it helps to save the bugs and
project failure in the long run.
A natural question that occurs to designer is in what way the
conventional C programming for PC is different from the C programming
with Keil or C51 programming. The basic objective of the conventional
Integrated Development Environment 21
C programming language was to make it work on the PC architecture
with a high level interface. Therefore, it does not support direct
access to registers. However, unlike the conventional C program-
ming on PC, most of the microcontroller-based embedded systems
applications demand reading and setting or resetting of single bits,
or Boolean processing. The second main difference is the program-
ming environment. Conventional C operated under the umbrella of an
operating system may be Linux or Windows, wherein there is a pro-
vision of system calls the program may use to access the hardware.
Almost all the programs written with microcontroller are for direct
use where the while(l) loop is common. The above-mentioned differ-
ences are bridged in Keil compiler by adding several extensions to
the C language, e.g., connecting of interrupt handlers. A good web-
resources are available on this topic at www.massey.ac.nz/~chmessom/
Chapter%206%20C%20Progr ammingFinal.pdf
2.3 Development Flow for the Keil IDE
The evaluation version of the Keil IDE for MCS-51 family (also
known as C51 evaluation software) can be downloaded from the website
www.keil.com. One can go up to a limit of 2 Kbytes of object code
with the evaluation version. Once the Keil IDE is installed, a short cut
appears on the desktop.
Step 1: Interfaces Offered by Keil IDE
After clicking on the above shown shortcut the following steps
should be carried out. The first blank window will appear as shown
in Figure 2.1.
You will be working with three windows presented by the Keil IDE.
The first is target toward the extreme left of the screen which is blank
at the moment, but will be updated as you go on working with the
project. The source file, register header file, and the target microcon-
troller chosen is displayed here. The bookmarks for the user such as
data sheet, user guides, library functions, etc., forms a ready reckoner
for the developer. The program window which occupies most of the size
of your screen displays the source code in C. At the lowermost end of the
screen, an output window is presented which gives information regarding
the errors and other output messages during the program compilation.
Open a new text file for writing your source code. This file has to be
saved with .c extension. This source code file will be ultimately added
22
Development Flow for the Keil IDE
9 1 ' trial MViBion2
B®(S
git E<fc g«w wojttt B*lx»g Fljsh Ptrtpht. *te Took £MC5 windo* Hrip
^G»B0 /4 '. *r
dM
|'J ,£,$ |[iQ|S|- *> &
k£|T«d*1
-^-l,d ^^^^^^^^^^^^^^^
. stert
(£' tna - |,Viqo-li
Figure 2. 1 The starting interface of Keil IDE
into your project to be opened as per step 2. The addition should be
done as per the instructions given in step 5.
Step 2: Opening a New Project
Here you can give a meaningful name for your project. After saving it
will create a folder which will store your device information and source
code, register contents, etc. Figure 2.2 shows a project opened with a
name trial.
Step 3: Selecting a Device for the Target
After completing step 2, Keil will give an alert to select the device.
The (iVision 2 supports 45 manufacturers and their derivatives. In the
exercise given in this book we have selected Atmel's 89S52 microcon-
troller as a target.
Step 4: Copying Startup Code to Your Project
The "startup. a51" will be added automatically to your project from
the Keil library "c:\keil\c51\lib" to [c:\keil\c51\EXAMPLES\HELLO\
ctrial\STARTUP.A51].
Integrated Development Environment
23
i'T' trial uYision?
d BS H & A '*
£ ■© |[rE[jS| e fer
_ - x
n Xs|T«grt1
•J*
1j Source Group 1
rS 1 -. (jJb...
Ftename [ftaTf
5«v* «tKP*: |PtaiedFi»i:r'*-2|
~ NBJiACwrr»lAFindnBw f
f
m
, Stan ■*> ^ * GMd D'h-e
■IcrrvJ^i "lucsoUWo... ^nrt uvu:ww> ^1 T fc36PH
Figure 2.2 Opening a new project
R' tria.11 (jV is ion 2
Fie £d(t Vtew Eroject Qebug Pfeh Peripherals Took JVCS fijndw tjelp
Select Device for Target 'Target 1"
I* £j Target
[=1 Files
CPU
Vendot: Almel
Device: ATSB52
Far*: MCS-51
Database
r U» Extended Linker (1X51 ) instead ol BL51
r * Extended/ lofA51
Description:
□ AT89C55V/D
-
£}AT89F51
DAT83F52
CJ AT89LS51
-
□ AT89LS52
Q AT89LV51
CJ AT83LV52
■ AT83LV55
D AT89LV55WD
DAT89S4D12
Cj AT89S51
_jQ
DAT89S53
-
i
>
8051 bawd RJ State CMOS control* with 32 WQ itm, 3 Timer ttourfe
8 K ROM Memory, 25E Bytes On-chip RAM
Cancel
~\ \R>Mfi Conwand A Find * Fles /
:
„ start
w
GMei Drive J My Computer IV MicrosottWo... pT>" trial 1 -uvbi... ^j>?* 2:39 PM
Figure 2.3 Selecting a device for the target
24
Development Flow for the Keil IDE
0. Irial1 |jVi*ion2 [C:\Docunients and Se1ting3\OWNERV)esklc>p\kei!\STARTUP.A51]
|)Fte £dt View Project Qabug Rash Perphwak lads £/CS Wndow Help
_ 6> X
n*
<£ m m * | » jfcpF^n
^J
- H3 Source&oupl
if
FiM |^ u3e~
(■0HQD51
Ibis file is pact of che C51 Cokpilec package
Cepyci.ght (c) 1988-2005 Kail Elakttoniis GafcH and Kail Software, Inc.
Vacsion 9.01
*** <« Use Configuration Uisaid in Context Menu >» TT '
STARTUP »A51: This code is executed after processor ceset.
To translate this file use A51 vich che following invocation:
AS I STARTUP. AS 1
To link the Modified STARTUP. OBJ die to youx application use the following
L:<51 Invocation;
S
1
For Help, press Ft
■*" 'ZFal Drive
J MyuJTOuler Mc-csoft Ao... f!i* tnall -||WI9.
R/W
Figure 2.4 Copying startup code to your project
Step 5: Adding Your Program Source Code
To accomplish this, follow the steps:
■ Right click "source group 1" followed by
■ Choose "Add Files to Group 'Source Group 1"'
■ Set "Files of type" to "All files (*.*)"
■ Select "Startup. a51"
Observe the files getting updated in the target window. You will have
to double-click on the C source file name displayed in the target window
to view it.
Step 6: Configuring and Building the Target
Right click on target 1 in the target window, select the option for
target 1, a window to choose the options for the target will be displayed.
Here you can choose the microcontroller frequency, listing of files, output
in hex, debug information, etc.
The important point here is choosing the appropriate memory model.
Integrated Development Environment
25
triall vVteionl [C:\Documents and Settings\OWNER\Desktop\keil\STARTUP.A51]
[^Fie e* y&n Project Debug flash Peripherals loot gvcs window Help
to s a cp «6 fe
- h" 1 x
-|j|x|
^M
- ?J Target 1
- ta_
1
ikhddsi
; TMs tile is east o£ th
ce for Target Target 1'
Options Fcr Group 'Source Group 1'
C5l Compiler package
Kei.1 Elekcconik GabH and Keil Software, Inc.
Oper Tile
fgjgebuH target
^BuH target
£ :tco byild
FT
Add Fibs to Grotp "Souic? G'cuo I"
IergetSj Groups,, Ffas...
Fit* Id? RejTMveGroLp 'Source Group i' and t'sFfej
n «i sard in Context Henw >» ***
is executed after processor reset.
st A51 with Che following invocation:
IP.OEJ flit to yrjr ami LCftdOD USE the fcllcwiri]
^ Include Dependencies
^
~| \ B«iM fcCanwmi /, Fid .■■ R« /
^
Add Fits to current Project Group
R/W
" . ' :l I ' ■■
J My Compute W Microsoft Wo... H»' trial! - ..
Figure 2.5 Adding your program source code
As per the on-line Keil IDE manual [28] C51 currently supports the
following memory configurations:
■ ROM: currently the largest single object file that can be produced
is 64 K, although up to 1 MB can be supported with the BANKED
model described below.
■ All compiler output to be directed to EPROM/ROM, constants,
look-up tables, etc., should be declared as "code".
■ RAM: There are three memory models, SMALL, COMPACT, and
LARGE
■ SMALL: all variables and parameter-passing segments will be
placed in the 805 l's internal memory.
■ COMPACT: variables are stored in paged memory addressed by
ports and 2. Indirect addressing opcodes are used. On-chip
registers are still used for locals and parameters.
■ LARGE: variables etc. are placed in external memory addressed by
@DPTR. On-chip registers are still used for locals and parameters.
26
Development Flow for the Keil IDE
;■■•' 1 1-.. i i 1B *\owNra\fic-.M 1 .|
Qm* {« v*m from Djibug Pi** P***** Took SvCS window Htto
Options for large! ' larsel 1'
c
IB iiu
B««_(d
Device Target | Qjipul Lelng C51 | A51 | BL51 Locale | BL51 Mac | Debug | UUtes |
AbnelATB9E51
Xl«l(MHz|: [SB U» OrvcNp flOM (ftiO-OtfFF)
Memory Modot Smai variable* r> DATA
Code Rom Sue: I Largs 84K progiarn
Opmting syttan Norte
"3
3]
OK
Coned Default*
~I \i»HA ComnwdA RrcuRkt /
- * X
_ a x
Ulf-chio Co* nenoty
Eprom |
Epnm
Start
See:
OH-chip xdoto irnomoij'
Start . :*
1
Ram T
L
R«r,r
Ran,p
r Cede Banking
BonkAiM |
Start
End;
V
V
B«**r
^
3
d
Figure 2.6 Configuring and building the target
Table 2.1 Choosing the best memory model for your C51 program
Model
RAM supported
Best for
Worst for
Small
Compact
Large
Total RAM 128 bytes
(8051/31)
256 bytes off-chip, 128
or 256 bytes on-chip
64KB, 128, or 256
bytes on-chip
Code size up to 4 K
High stack usage, pro-
grams with large num-
ber of medium speed
8-bit variables
Easiest model to use
Global variable (be
kept minimum)
Rarely used in
isolation, usually
combined with the
SMALL switch
reserved for
interrupt routines.
Never used in
isolation, combined
with small and
compact
BANKED: Code can occupy up to 1 MB by using either CPU port
pins or memory-mapped latches to page memory above x FFFF.
Within each 64 KB memory block a COMMON area must be set
aside for C library code. Inter-bank function calls are possible.
Integrated Development Environment
27
? T ' Trail |jVis1on2 [C:\DocumenU and S«tting$lOWNER\DeskT©p\kellto.c]
£\m E* Sw» Prow* Qebua Rs* Perjpbsrab loots SVCS Wndw Hob
* £fe
£J /4 9fc|
^*
• «l CIS 6fe ft
, ; t \ Tanatl
'
:_i
-^ Sourcs Group 1
£] STMTUP.A51
- j£|M
Q resh.h
Br*. Iff UiTT JjL J
// Sinpie ptogcaa explain the Pott ConCiguracilon of the
// TC3-51 Faaily. Which outs the data.
*!inrluJ»<neg52.h>
void main(void)
{
P1-0K22;
P2-5X33J
}
Oil*
_|gJ jC|
1
^
3
Build target 'Target 1'
compiling a.c. . .
linking. . .
Program Size: data-9.0 xdata-0 code-22
"trail" - Q Error (a). Warning (a).
~| VIMWA ConffWHlA FWinFlM /
L:B C:5
u
R/W
- GMeriDl
i |f» trail - t*VWon
Figure 2.7 Compiling your program by pressing F7
Step 7: Compile Your Program by Pressing F7
Either press F7 or click on build target in the target window to compile
your program. The output window will show the errors or warnings if
any. You can also see the size of data, code, and external data, which is
of immense importance since your on-chip memory is limited.
Step 8: Working in Simulated Mode
Once the program is successfully compiled, you can verify its func-
tionality in the simulated mode by activating the debug window. For
this press CTRL + F5 or go to the menu option "Debug" and select
"Start and Stop Debug Section". Press Fll for single stepping or F5
for execution in one go. Go to the menu item "Peripheral" and select
the appropriate peripherals to view the changes as the program starts
executing.
Terminating the debug session is equally important. Click on "stop
running" or ESC key to halt the program execution. You can make
the changes to the program after coming out from the debug session
28
Development Flow for the Keil IDE
Iruil ■ fjVnion? [C \Documenls and Settings \OWNER\Desklop\keil\d.cl
Q* tdlt JTIew Protect Qebug Flash Peripherals look JVC5 W«oW tNo
'_ rT X
-1*1 x
^1
Interrupt Sytlom
^ t V n fc p
// Staple pcag cut explain the Poet. Configur >CLian aC
ft HC3-51 Family. Hblca outs zht data.
J include<r egS2 . h>
11^ ff... [IJJB I j«
Running in Eval Mode (2
Load "C:SSReilNNtraal"
Vccta Mode j Reg 1 Ena | Pri [
0003H
OOOGH
JUIJH
001 BH
QD23H
QQ23H
r ea
Satoc tad Intern^*
r ito r ieo
r EXD Ph:[ft
3
Parallel Port v 1
Pet 2
P£|Qx33
Pew 0*33
7 BUt
rrwwrrw
s.^ ^-
P.ii.illelPuri 1
Pat"
PI- 0x22
7 Bite
I I kll I M
Ptor|OC2 | | kl I I kl
1
ASM ASSIGN BreakDisable BreakEnable BreatKill BreekList BreakSet BreakAccess
I -H^IH^I V lMMAriiiiiiiA Rn.it He«~7 ~ ~~ Hi
L:7C!l
IVW
, start ■-'
- ..'■IjlL-i
pi- -I-V ■ :. • ■
- j n
Figure 2.8 Simulation mode of Keil
by pressing start /stop debug session. Few iterations through the
above-mentioned process will make your program completely bug- free
and save your time and other resources on the actual hardware.
Step 9: Actual Dumping of the Code
in Microcontroller's On-chip Memory
There are different mechanisms for this. Some programmers use ready-
made programmers to program the microcontroller. If you are interested
in purchasing one for your project, the list is enclosed. Design of vari-
ous programmers has also been given at Wichit Sirichote's webpage at
http://www.kmitl.ac.th/~kswichit%20/.
Chapter 3
Art of C Programming for Microcontrollers
There are large number of textbooks and data sheets which give
an overview of 8051 architecture, pinout, and other peripheral details.
However, with the Keil IDE, you can take the benefit of the header
files and need not remember the details like the port address, timer
counter addresses, etc. The CA51 Compiler Kit for the 8051 microcon-
troller family supports all 8051 derivatives including classic devices and
IP cores from companies like Analog Devices, Atmel, Cypress Semicon-
ductor, Dallas Semiconductor, Goal, Hynix, Infineon, Intel, OKI, Philips,
Ailicon Labs, SMSC, STMicroelectronics, Synopsis, TDK, Temic, Texas
Instruments, and Winbond.
3.1 Familiarizing with Your Compiler
Capabilities
The C for microcontrollers and the standard C syntax and seman-
tics are slightly different. The former is aimed at the general purpose
programming paradigm whereas the latter is for a specific target micro-
controller such as 8051. The underlying fact is that everything will be
ultimately mapped into the microcontroller machine code. If a certain
feature such as indirect access to I/O registers is inhibited in the target
microcontroller, the compiler will also restrict the same at higher level.
Similarly some C operators which are meant for general purpose com-
puting are also not available with the C for microcontrollers. Even the
operators and constructs which may lead to memory inefficiency are not
available in C programming meant for microcontrollers. Be aware that
the target code should fit in the limited on-chip memory of the proces-
sor. Even the I/O functions available in standard C such as printf() or
scanf() are either not made available in C compilers for microcontrollers
or advised not to use them. These functions eat up lot of memory space
and are not time-efficient owing to the dragging of supporting func-
tions like floating point routines and lot of delimiters. Another striking
difference in case of embedded systems programs is that they do not
29
J.S. Parab et al. (eds.), Exploring C for Microcontrollers, 29-36.
© 2007 Springer.
30 Whether to Use Headers or Not?
have the umbrella or support of the operating system. The programmer
has to be accustomed with the absence of system calls which makes life
easy in traditional C.
The C for microcontrollers is more closer to the assembly language
than the conventional or traditional C. Few examples to support the
above statement are presence of arithmetic/logic/bitwise operations to
resemble machine operations, Use of pointers which corresponds to mem-
ory access at machine level etc. The detailed information regarding the
features of 'C supported may be found in the document C x 51 Compiler
User's Guide for Keil Software [28].
3.2 Whether to Use Headers or Not?
As a professionally embedded systems developer one can write a stand-
alone 'C code, requiring no header files, and it will compile correctly with
the Keil C51 compiler. However, this requires a through study of the tar-
get microcontroller architecture. With the large number of derivatives
of the 8051, it is difficult to remember the on-chip resources, e.g., the
MCS-51 versions from Atmel such as AT89C2051 or AT89C51 have two
timers while the other members such as At89C52 or AT89S53 have three
timers. Therefore, although there is little memory space overhead, it is
advisable to use the header files which defines all the on-chip resources
for the target microcontroller, e.g., whenever you choose the target de-
vice such as AT89C52, Keil IDE gives the information regarding all its
on-chip resources in the window at the right side as shown in Figure 3.1.
You can observe another advantage of working with the header file.
Define the header file <REG51.h> or <REG52.h> in the program win-
dow and select the target device as 80C51. Now open the header file,
which will reflect all the on-chip resources of 80C51 as shown below:
/•
REG51.H
Header file for generic 80C51 and 80C3f microcontroller.
Copyright © 1988-2002 Keil Elektronik GmbH and Keil Software, Inc.
All rights reserved.
#ifndef __REG51_H„ sbit EX1 = OxAA;
#define __REG51_H__ sbit ETO = 0xA9;
/* BIT Register */ sbit EXO = 0xA8;
/* BYTE Register */ /* PSW */
sfr P0 = 0x80; sbit CY = 0xD7; /* IP */
sfr PI = 0x90; sbit AC = 0xD6; sbit PS = OxBC;
Art of C Programming for Microcontrollers
31
sfr P2 = OxAO;
sfr P3 = OxBO;
sfr PSW = OxDO;
sfr ACC = OxEO;
sfr B = OxFO;
sfr SP = 0x81;
sfr DPL = 0x82;
sfr DPH = 0x83;
sfr PCON = 0x87;
sfr TCON = 0x88;
sfr TMOD = 0x89;
sfr TLO = 0x8A;
sfr TL1 = 0x8B;
sfr THO = 0x8C;
sfr TH1 = 0x8D;
sfr IE = 0xA8;
sfr IP = 0xB8;
sfr SCON = 0x98;
sfr SBUF = 0x99;
sbit TB8 = 0x9B;
sbit RB8 = 0x9A;
sbit FO = 0xD5;
sbit RSI = 0xD4;
sbit RSO = 0xD3;
sbit OV = 0xD2;
sbit P = OxDO;
/* TCON
sbit TF1
sbit TR1
sbit TFO
sbit TRO
sbit IE1 =
sbit IT1 =
sbit IEO =
sbit ITO =
= 0x8F
= 0x8E
= 0x8D
= 0x8C
= 0x8B;
= 0x8 A;
= 0x89;
= 0x88;
/* IE *
sbit EA = OxAF;
sbit ES = OxAC;
sbit ET1 = OxAB;
sbit TI = 0x99;
sbit RI = 0x98;
sbit PT1
sbit PX1
sbit PTO
sbit PXO
OxBB;
OxBA;
0xB9;
0xB8;
/* P3 V
sbit RD = 0xB7;
sbit WR = 0xB6;
sbit Tl = 0xB5;
sbit TO = 0xB4;
sbit INT1 = 0xB3;
sbit INTO = 0xB2;
sbit TXD = OxBl;
sbit RXD = OxBO;
/* SCON V
sbit SMO = 0x9F
sbit SMI = 0x9E
sbit SM2 = 0x9D
sbit REN = 0x9C
#endif
triad uVision? [Texl2]
[Uete E* S*w Eroject G*ufl >%** Perjpherab look £VC5 HJndow tMp
Sg£H
Options for Target 'Target 1'
c
- :-J Target
Files
- J X
- \& x
Device | T*flftt | Output | Ltstng | CS1 A51
Database: |~~
Vendor Atroel
Device: AT89C52
Famly; MCS-51
BL51 Locate BL51 Msc | Debug | UtiWe« |
r U*e Extended Linker ILX51) instead of BLS1
_| AT83C51R C
l iaiaaaaJ
_J AT89C55
_]AT89C55v/D
_JATB9F51
QAT89F52
_J AT89LS51
CJ AT89LS52
DAT89LV51
_|AT89LV52
LJAT89LV55
LJAT89LV55WD
[J AT89S4D12
~1 ATfWRI
v
6051 beted Ful S lafc CM OS controter with T hree-Levd Program Memory Loci
32 I/O lines, 3 Timers/Counters, B Interrupts souces
8 K Flesh Memory, 256 Bytes Orvchp RAM
OK
Cancel
Defaults
H i MM A Command A Find h Bet T
GMail r ■ f My Computer U" Microsoft Wo,,. fl'tn-jl] -|jVisi,
1
R/W
Figure 3.1 On-chip resources in the window
32
Whether to Use Headers or Not?
Now select another target device 80C52. This device has three timers.
Now the header file will automatically update the database of on-chip
resources pertaining to this device as shown below.
REG52.H
Header file for generic 80C52 and 80C32 microcontroller.
Copyright © 1988-2002 Keil Elektronik GmbH and Keil Software, Inc.
All rights reserved.
#ifndef __REG52 _H__
#define __REG52 _H_.
/* BYTE Registers *
sfr P0 = 0x80;
sfr PI = 0x90;
sfr P2 = OxAO;
sfr P3 = OxBO;
sfr PSW = OxDO;
sfr ACC = OxEO;
sfr B = OxFO;
sfr SP = 0x81;
sfr DPL = 0x82;
sfr DPH = 0x83;
sfr PCON = 0x87;
sfr TCON = 0x88;
sfr TMOD = 0x89;
sfr TLO = 0x8 A;
sfr TL1 = 0x8B;
sfr THO = 0x8C;
sfr TH1 = 0x8D;
sfr IE = 0xA8;
sbit EXO = IE A 0;
IP
A
sbit PT2 = IP A 5;
sfr IP = 0xB8;
sfr SCON = 0x98;
sfr SBUF = 0x99;
/* 8052 Extensions */
sfr T2CON = 0xC8;
sfr RCAP2L = OxCA;
sfr RCAP2H = OxCB;
sfr TL2 = OxCC;
sfr TH2 = OxCD:
/* BIT Registers */
/* PSW */
sbit CY = PSW A 7;
sbit AC = PSW A 6;
sbit FO = PSW A 5;
sbit RSI = PSW A 4;
sbit RSO = PSW A 3;
sbit OV = PSW A 2;
sbit P = PSW A 0;
//8052 only
sbit RCLK =
T2CON A 5;
sbit TCLK =
T2CON A 4;
/* TCON
sbit TF1
sbit TR1
sbit TFO
sbit TRO
sbit IE1 =
sbit IT1 =
sbit IEO =
sbit ITO =
= TCON A 7
= TCON A 6
= TCON A 5
= TCON A 4
= TCON A 3;
= TCON A 2;
= TCON A l;
= TCON A 0;
/* IE */
sbit EA = IE A 7;
sbit ET2 = IE A 5;
//8052 only
sbit ES = IE A 4;
sbit ET1 = IE A 3
sbit EX1 = IE A 2
sbit ETO = IE A 1
Art of C Programming for Microcontrollers
33
sbit PS = IP A 4;
sbit PT1 = IP A 3;
sbit PX1 = IP A 2;
sbit PTO = IP A 1;
sbit PXO = IP A 0;
I* p3 *i
sbit RD = P3 A 7;
sbit WR = P3 A 6;
sbit Tl = P3 A 5;
sbit TO = P3 A 4;
sbit INT1 = P3 A 3;
sbit INTO = P3 A 2;
sbit TXD = P3 A 1;
sbit RXD = P3 A 0;
sbit EXEN2
T2CON A 3;
sbit TR2 =
T2CON A 2;
sbit C.T2 =
T2CON A l;
sbit CP _RL2
T2CON A 0;
#endif
/* SCON
sbit SMO
sbit SMI
sbit SM2
sbit REN
sbit TB8
sbit RB8
sbit TI =
sbit RI =
= SCON A 7
= SCON A 6
= SCON A 5
= SCON A 4;
= SCON A 3;
= SCON A 2;
SCON A l;
SCON A 0;
/* pi 7
sbit T2EX = P1 A
//8052 only
sbit T2 = P1 A 0;
//8052 only
i;
/* T2CON 7
sbit TF2 = T2CON A 7;
sbit EXF2 =
T2CON A 6;
Note the bold letters which are exclusively added for the 80C52 only.
34 Differences from ANSI C
In nutshell the first program sentence will be always a statement
^include <reg51.h> for MCS-51 family. The standard initialization
and startup procedures for the 8051 are contained in startup. a51. This
file is included in your project and will be assembled together with
the compiled output of your C program. For custom applications, this
startup file might need modification, because the stack or stack space,
etc., are predefined as per the memory model.
3.3 Basic C Program Structure
Listing below shows a basic structure for a C program.
//Basic blank C program that does nothing
// Includes
^include <reg51.h> // SFR declarations
void main (void)
{
while(l);
{
body of the loop // Infinite loop
}
} // match the braces
Note: Similar to conventional C, all the variables must be declared at
the start of a code block, you cannot declare variables in the midst of
the program statements.
3.4 Differences from ANSI C
There are marginal differences of Cx51 compiler from the ANSI
C compiler. These differences are twofold, viz. compiler related and
library related. The details are given in the help menu of the Keil
IDE. Frequently used things are given below for ready reference of the
programmers.
Variable Types
The Keil C compiler supports most ANSI C variable types and in
addition has several of its own.
Art of C Programming for Microcontrollers
Standard Types
35
Only floating point variable types of ANSI C are not supported by
Keil C compiler as the basic 8051 core is not efficient for the same. The
types supported are as follows:
Type
Bits
Bytes
Range
Char
8
1
-128 to +127
Unsigned char
8
1
to 255
Enum
16
2
-32,768 to +32,767
Short
16
2
-32,768 to +32,767
Unsigned short
16
2
to 65, 535
Int
16
2
-32,768 to +32,767
Unsigned int
16
2
to 65, 535
Long
32
4
-2, 147, 483, 648 to 2, 147, 483, 647
Unsigned long
32
4
to 4, 294, 697, 295
Keil Types
The bit and Boolean capabilities of MCS-51 family are well explored
by the Keil C Compiler by adding several new types. Some of them are
as follows:
Type
Bits
Bytes
Range
Bit
1
to 1
Sbit
1
to 1
Sfr
8
1
to 255
Sfl6
16
2
to 65, 535
Of these, only the bit type works as a standard variable. The other
three have special behavior that a programmer must be aware of. The
bit type gets allocated to the 805 l's bit-addressable on-chip RAM. Note
that you cannot declare a bit pointer or an array of bits. The special
function registers are declared as a sfr data type in Keil C. If you give
the address of the SFR as 0x80h then it gets allocated to port of
8051. Extensions of the 8051 often have the low byte of a 16 bit register
preceding the high byte. Therefore the timer for instance should be
declared as a 16-bit special function register, sfr 16, giving the address of
the low byte:
sfrl6 TMRORL = 0x8A;
sfrl6 TMRO = 0x8B;
// Timer reload value
// TimerO lower
36
Differences from ANSI C
Keil Variable Extensions
In consistent with the 8051 architecture Keil offers various types of
variable extensions. Following table summarizes the same. Assembly
language mnemonics are used to indicate the subsequent meaning of
the variable extension used.
Extension
Memory Type
Related ASM
Data
Directly-addressable data mem-
ory (data memory addresses
0x00-0x7F)
MOV A, 056h
Idata
Indirectly-addressable data
memory
MOV R0, #09Ah
(data memory addresses
MOV A, R0
OxOO-OxFF)
xdata
External data memory
MOVX @DPTR
Code
Program memory
MOVC ©A+DPTR
In case the memory type extension is not specified, the compiler will
decide which memory type to use automatically, based on the memory
model (SMALL, COMPACT, or LARGE, as specified in the project
properties in Keil).
Chapter 4
Exploring the Capabilities of On-Chip
Resources Programming for I/O Ports,
Interrupts and Timer/Counter
4.1 Importance of Ports
Ports are the means through which the microcontroller communi-
cates with the outside world. They are the most common I/O devices.
An interesting point to note is that the number of I/O pins or ports
are decided by the packaging style of the microcontroller. A compari-
son of various packages is given below: A new trend in 8-bit controller
design is to place the chip inside a 20-, 16-, or even 8-pin PDIP or SOP
package, allowing for very small and cheap embedded systems to be
constructed [29].
Fortunately most of the derivatives of the 8051 are generally offered
in 40-pin DIP or 52-pin PLCC packages and there is not much varia-
tion in terms of package pinouts. The obvious advantage of the upward
compatibility maintained into the different versions of the 8051, is
the direct replacement of the latest advanced 8051 from Intel to its
cheap predecessor without even changing the printed circuit board.
This "drop-in" replaceability is rarely true of other microcontroller
architectures [30].
Playing with the Ports
Program 4.1: Simulated Port Testing Using Keil
The program illustrates simple port programming in a simulated mode
using the Keil compiler. A sample data is sent to the port and the output
is observed in the simulator window. You may as well connect LEDs to
observe the output.
37
J.S. Parab et al. (eds.), Exploring C for Microcontrollers, 37-67.
© 2007 Springer.
38
Importance of Ports
Table J^.l Comparison of the packages
Package
Number of
pins
Features
Applications
PDIP (plastic
8-64
Through hole type
Prototype or
dual in-line
devices, dense style
hobbyist type
package)
package, pins/area
applications,
ratio of PDIP not very
smaller 8-bit
efficient
microcontrollers
PLCC (plastic
20 up to
Through hole type
Small,
leaded
80+
devices
low-pincount
chip-carrier)
microcontrollers
SOIC (small
8-64 pins
Pins are spaced much
outline
closer together,
integrated
package designed to be
circuit) or
soldered directly to the
"SOP" (small
top of a board
outline
package)
QFP (quad flat
8-220+
Sophisticated soldering
16- to 32-bit
package)
pins
workstation required to
microcontrollers
deal with the pins
to 64-bit
closely spaced
superscalar
microprocessors
Program Source Code
#include<reg51.h>
void main(void)
{
PI =0x44;
P2=0x55;
}
/* special function register declarations for the
intended 8051 derivative. The header file
contains the definitions of special function
registers (SFRs) and other functions. */
// Start of the Main function.
/*Send 44H to port PI*/
/*Send 55H to port P2*/
// End of the main function.
The screenshot of simulation window shown in Figure 4.1 the data
delivery to port 1 and 2.
Exploring the Capabilities of On- Chip Resources Programming
39
PP" triaM |jVision2 [C:\Documents and Settings\OWNERWesktop>keil\trial1 .c]
File £d* View Project fcebug Flash Peripherals loots 3VCS ^ndow &*>
(asm ojs «& fc
-il^C*
-S XI
^#*
K#m
^jxj
3]
Register
Value
- Regs
rO
rl
r2
*
;
- Sys
a
b
OkOO
OkOO
OkOO
OkOO
OkOO
OkOO
OkOO
OkOO
OkOO
0x00 a
Irks #.„ ^B...
#include<reg5i.h>
void nain(void)
{
r Pl-0x44;
P2-0X55;
/* special function register declarations
for the intended 8051 derivative.
The header file contains the definitions of Special
Function Registers (SFRs) and other functions. •/
// Start of che Rain function.
/•Send 44H to pott Pl*/|
/•Send SSH to port P2V
)
J±
Parallel Port 1
Port!
« rs^T- 7 Bin
pbK |ok44 ri?rrrr5rr
Parallel Port 2 X
Port2
PZ 0x55
7 B»»
1 ki ki i*r r*
n*rMrr*n?
PhK|0x55
31
ajlRunning with Code Size Limit: 2K
J Load "C:\\Documents and Settings\\OWNER\\Dosktop\MceilN\triaLl"
ASM ASSIGN BreakDisable BreakEnable BreakKill BreakList BreakSet BreakAccess
Bu4d A C*mrnmd /, find in Bet / ~|L*
Ready
L:8C:44
. start
•*■ GMail Drive
J My Computer
IV MkfOSoftWO..,
$
RJW
I* trial!
Figure 4-1 Screenshot of simulation window showing the ports
Program 4.2: Sending Out Different Contents to Port 1
Different data bytes are sent to port 1 after delay. The results can be
checked in the simulation window, which shows the changing of data on
the port 1 lines.
Program Source Code
#include <REG52.H>
void delay (void);
void delay (void)
{
int i;
for (i=0;i<30000;i++);
for (i=0;i<30000;i++);
}
invoking delay function
40
Importance of Ports
void main (void)
{
while(l)
{
PI = 0x01
delay ();
Pl= 0x02;
delay ();
Pl=0x04;
delay ();
Pl=0x08;
delay ();
Pl=0xl0;
delay ();
Pl=0x20;
delay ();
PI =0x40;
delay ();
Pl=0x80;
delay ();
Pl=0x40;
delay ();
Pl=0x20;
delay ();
Starting of the main function.
Out 01 on the port 1.
Delay function.
Out 02 on portl.
}
Pl=0xl0;
delay ();
Pl=0x08;
delay ();
Pl=0x04;
delay ();
Pl=0x02;
delay ();
Pl=0x01;
delay ();
}
termination of the while loop,
termination of the main function.
Exploring the Capabilities of On- Chip Resources Programming
41
Program 4.3: Generating Square Wave on the Port
A number is assigned to port 1 which simulates input operation. The
port 1 contents are complemented and sent to the port 1. The square
wave can be observed on port 1 by using CRO.
Program Source Code
#include<reg51.h>
void delay (int);
void delay (int k)
{
int i,j;
for (j=0;j<k+l;j++){
for (i=0;i<100;i++);
}}
void main (void)
{
int N1=0;
number.
while(l)
{
P1=N1 ;
Nl =~N1;
delay (10);
PI = Nl;
delay (10);
// Start of the main function.
Defining the integer value for the
// Infinite loop
: Assign Nl to port PI*/
/* Complement Nl*/
/* Delay which defines the on and
off time for the Square wave. */
/*Send it to port PI*/
}
End of while loop.
}
End of main.
42
Importance of Ports
Program 4.4: Sending Data to the Ports by Assigning
Values to a Character
This program illustrates assigning values to the character and then
sending it to the port. Here the characters a, b, c are assigned with the
Hex numbers and these values are sent to ports.
Program Source Code
#include<REG51.H>
void main(void)
{
char a,b,c;
Define the characters a, b and c.
}
while(l)
{
}
a=0x01;
b=0x02;
c=0x03;
P0=a;
Pl=b;
P2=c;
Assign 01H to 'a' */
Assign 02H to c b' */
Assign 03H to 'c' */
Send value assigned to 'a' to port :
Send value assigned to 'b' to port 1 :
Send value assigned to c c' to port 2 H
Program 4.5: Configuring the Ports as Input
By default all the ports act as output port. They can be configures
as input by writing FFH to them. The programmer need not bother
about the actual SFR address. Thanks to the header file included at
the top.
The actual input operation is simulated by assigning values to the
variables. The actual DIP switch interfaced as input device is covered
further in the text.
Program below illustrates the simplest way to define the ports as an
input port and how to read the input from the ports and the result is
observed in the simulation window.
Exploring the Capabilities of On- Chip Resources Programming
43
Program Source Code
#include<REG52.H>
void main (void)
{
char N1,N2,N3;
P0=0xFF;
Pl=0xFF;
while(l
{
Defining the characters.
set PO as input
// set PI as input
I
}
N1=P0;
N2=P1
N3=N1+N2;
P2=N3;
Input value of PO in Nl*/
'Input value of PI in N2*/
Addition of the two inputs
Send value of N3 to port 2*
Program 4.6: Software Delay Loops Combined
with I/O Ports
The program demonstrates generation of software delay using two
loops operating on a single count. An integer x is declared and assigned
a count equal to 10,000. "While(l)" loop keeps the program in continues
loop. The other two loops are conditional with the first loop executes
when "while(x > 1)" is valid, i.e., when x is greater than 1. The other
loop executes when x is less than 10,000. Note the usage of decrement
( ) and increment (++) operators. Both these loops are embedded in
the main loop.
To observe the output of this connect the port 1 to LEDs. The output
can also be verified in the simulator window.
Program Source Code
^include <reg51.h>
void main (void)
44 Importance of Ports
{
int x = 10000;
while(l)
{
while(x > 1) /* 10000 count delay */
{
PI = OxOf; /* set leds on PORT1 to 00001111 */
x--; /* decrement x */
} // end of first loop
while(x < 10000) /* 10000 count delay */
{
PI = OxfO; /* set leds on PORT1 to 11110000 */
x++; /* increment x */
} // end of second loop.
} // End of open loop.
} // End of main.
Program 4.7: Alternate Method of Software Delay
Generation with Port Programming
This program illustrates the use of "FOR" construct for delay gener-
ation which toggles only one port pin (Pl.l).
Note the use of ! operator for complementing the variable.
Program Source Code
*& *& *& ^i^ *& *& ^i^ *& *& ^i^ *& *& *& *& *& "^c "^^ *& ^^ *& ^i^ *& *& ^i^ *& *& *& *& *& "^c *& *& "^c "^c "^c "^c *& *& "^c *& *& *& ^i^ ^^ *& *& *& "^c *& *& *& *& *& *& "^c *& *& "^c *& *& *&
#include<reg52.h>
sbit vin = P1 A ; //Pin declaration vin = port 1 pin
void main(void)
{
int i;
vin = 1; //Make port pin P1.0 high
while(l)
{
for(i=0;i<=3000;i++); // Delay generation
Exploring the Capabilities of On- Chip Resources Programming 45
for(i=0;i<=3000;i++);
vin = !vin; //complement port pin P1.0 after
delay
}
+5V
o
470 O
Controller
Port Pin
v^v LED
Figure 4-2 LED interface to microcontroller port pin
Program 4.8: Shifting the Port Contents to Left
This program shifts the contents of port to left. The result may be
seen in the simulation window by opening the menu option for periph-
erals. The port bits goes on changing one by one.
Program Source Code
#include <REG52.H>
void main (void)
{
int i;
char Nl;
while(l)
{
Nl=0x01;
while(Nl!=0x00) //Continue the loop till Nl not
equal to 00H
//When N1=00H program exits
the loop
{
46 LED Interfacing
for(i=l;i<10000;i++); //delay
P0=N1; //Send value of Nl to
port
N1=N1«1; //Left shift Nl by one
bit position
}
}
} /* try right shift by using right shift operator c >>' */
4.2 Simple Ideas for Port Expansion
The users are worried when the number of I/O port lines poses a bot-
tleneck for applications especially in the areas of robotics and industrial
process control. In these types of application domains the user may either
go for another microcontroller with more I/O pins or interface chips like
PPI8255 to the existing ports. However, there are many simple methods
to expand the port. Few of them tried by embedded system developers
are given herewith the source URL, so that the user may adopt them
for their applications.
■ 2 Wire Input/Output for 8051 type CPUs [31].
The application note explains the use 12 C bus interfaced to shift
registers for expansion of ports. 4094 shift registers have been used
with the additional feature of tri-state output at power up until
the CPU has written valid data, preventing power up "glitches" .
■ 8051 I/O expansion using common shift register chips [32].
The application note gives complete schematic and assembly code
to expand 8051 I/O using shift registers.
4.3 LED Interfacing
The simplest applications such as port testing or indication may only
require on/off-type LEDs for displaying status information. For such ap-
plications, LEDs can be controlled directly by a general-purpose I/O pin
capable of sourcing or sinking the necessary current required for lighting
the LED, typically between 2 mA and 10 mA. LEDs have exponential
voltage-current characteristics, that means around the operating point
there is rapid increase in current for little increase in voltage. Therefore
ideally a constant current source is desirable to drive the LEDs. How-
ever, the same can be simulated by using a series resistor connected to
the port pin so that the voltage across the LED will be fairly constant.
Exploring the Capabilities of On- Chip Resources Programming
47
■5V
3301 i
+Vcc
1 330Q
LED1 WV^ W W W W W W LED8
Figure 4-3 Interfacing diagram for a LED
Generally a common anode connection is chosen in a digital environ-
ment because pull-down is much easy as compared to push-up. If an
external power supply is used, then the corresponding brightness will be
much better as compared to driving logic 1 through the microcontroller
port pins. From a programmer's point of view this means by writing
logic '0' the LED will glow (see Figure 4.3).
Three things are required for working with the LEDs: the driving
voltage, the current to be passed, and the forward voltage drop across
the LED. For a blue LED with 12 V supply, in order to glow a single
LED, a current of the order of 20 mA is required to be passed. With the
forward voltage drop of 3.4 V, the value of the resistor can be calculated
using simple Ohm's law as follows:
R = Vs-Vl/I
Where Vs = the supply voltage
Vl = voltage across the LED
I = Current through the LED
48 Different Programs for LED Interfacing
The details of LED interfacing to microcontroller have been covered
at several references. The microcontrollers I/O port pin is configured as
an output. The choice of the series resistor and its wattage is covered in
many standard books.
4.4 Relevance of LEDs in Today's Lightening
Industry
Street lighting is fast emerging as a potentially strong market for
LEDs, since these devices have reached a level of output and efficiency to
make them viable replacements for incumbent lighting technologies. The
adavntages of LED-based street lights are reduced energy consumption,
less maintenance, and better light quality [33]. Novel interfacing tech-
niques based on microcontroller are emerging which ranges from simple
low-cost current limiting resistors to dynamic constant current utilizing
PWMs and analog-to-digital converters. With HB-LED lighting requir-
ing the use of low-voltage electronic control, low-cost microcontrollers
are useful in bringing additional compelling features to household light-
ing. Microcontrollers are making it easier for lighting designers to in-
corporate a reliable connectivity interface such as DALI and DMX512
that will provide the backbone for adding remote user controls [34] . The
above mentioned interfaces are based on packet-based system to deliver
the data to the LED matrix. The technique has been covered in depth
in this chapter.
4.5 Different Programs for LED Interfacing
Program 4.9: Blinking LED
This program illustrates simple LED blinking at a constant interval.
A simple technique of complementing a bit is used with changing soft-
ware delay. The hardware shown Section 4.3 is used.
Program Source Code
^include <REG52.H> /* special function register declarations
for the intended 8051 derivative */
void delay (void); /* declaring a delay routine for blinking
interval
void delay(void)
{
int i;
Exploring the Capabilities of On- Chip Resources Programming
49
for (i=0;i<30000;i++);
for (i=0;i<30000;i++);
}
void main (void)
{
bit my bit;
mybit = 1;
count
while (1
{
mybit = ! mybit;
PI = mybit;
delay ();
}
}
// invoking main function.
define the bit as a mybit.
assign the mybit a logic high
indefinite loop
complement the bit
send the complemented bit to port 1
invoke the delay routine
termination of the while loop
termination of the main function
Program 4.10: Scrolling LED
This program illustrates the interfacing of LED with scrolling pattern.
The display appears as if the LED is shifting. The LED connected to
the port glows one by one. A software delay is used to define scrolling
interval.
Program Source Code
*& *& *& *& *& *& *& "^c "^c *& ^i^ *& *& "^c "^c "^c "^c "^c "^c *& *& "^c ^i^ *& *& *& *& *& *& *& *& *& *& *& *& *& "^c *& *& "^c *& *& *& *& "^c *& *& *& *& *& *& *& *& *& *&
#include <REG52.H>
void main (void)
{
int i;
char Nl;
define the integer number
//define the character to assign the
hex number
while(l)
{
Nl=0x01;
while(Nl!=0x00)
{
for(i=l;i<10000;i++);
routine for scrolling interval
50
Different Programs for LED Interfacing
}
}
}
P0=N1; // display the LED corresponding
toNl
N1=N1>>1; //shift right by one
Note: Similarly one can write the program for the Shifting the LED
in the reverse order.
Program 4.11: Exploring Bit Capabilities
of the Microcontroller
This program makes use of the microcontroller's bit programming
capability. Here the single port pin is used as an output. The program
toggles the single port pin to give a continuous on/off pattern on pin
Pl.l. Input from P1.0 is simulated.
Program Source Code
"^l^ "^l^ *& *& "^l^ *& *& *& "^£ *& "^£ "^£ "^r£ *& *& *& "^£ "^l^ *& "^£ *& "^£ "^£ "^l^ *& "^£ *& "^£ *& "^£ "^£ *& "^£ *& "^C "^£ *& *& *& "^l^ "^l^ "^l^ "^l^ "£? "^£ *& "^£ *& "^l^ "^£ *& ^l^ *& *& "^l^ "^£ *&
#include<reg52.h>
sbit van= P1 A 0;
sbit new = P1 A 1;
void main(void)
{
int vinod;
vinod = 0x00;
while(l)
{
van = vinod;
new = vinod;
vinod=!vinod:
}
/* Pin declaration vinod = port 1 pin 0*/
/* Pin declaration new = port 1 pin 1*/
}
// Define the int vinod
Infinite loop (i.e.,countinuos loop)
Simulating input from port pin P1.0 and
assigning the same to character van */
/* send output to portl pinl */
//compliment vinod
// end of loop
// End of main
Exploring the Capabilities of On- Chip Resources Programming 51
4.6 More Projects on LED Interfacing
to Microcontrollers
Based on the programs given above many advanced projects are
possible. Given below is the list of project ideas, which can be explored
with little efforts by modifying the LED interfacing circuit.
4.6.1 Running LEDs
http://www.avrprojects. net/articles. php?lng=en&pg=43
The code for the running LEDs has already been developed in this
chapter. The project at the above URL describes running LED or LED
chaser project. It has running LED light with 15 red 3 mm LEDs. Just
have a look at the project and it is very simple to implement on our kit.
4.6.2 Running Bicolor LED
The above project can be very easily modified by connecting the
readily available bicolor LED package such as TLUV5300 (Refer:
www.vishay.com/leds/list/product-83056) which comprises green and
red LEDs. Different patterns can be created by modifying the source
code.
4.6.3 Interfacing 6 LEDs
Using 3 Microcontroller Pins by
URL: http://www.scienceprog.com/connect-6-leds-using-3-microcon
troller-pins/ A simple circuit is given for expanding the pin capabilities
useful when using dual colour LEDs, i.e., 2 LEDs packed in one case
but in different directions. AVR-GCC C code to control the LEDs is
also given. With the similar scheme even 12 LEDs can be connected by
using only 4 port pins.
4.6.4 The LED Dimmer Demoboard
http://www.standardics.nxp.com/support/boards/leddemo/
The LED dimmer demoboard demonstrates the capability of the I2C-
bus to perform red/green/blue color LED lighting and mixing opera-
tions. Two separate control cards comprise the demoboard:
■ The Keypad Control Card contains a microcontroller, a 16-key
keypad/controller, and a power supply/regulator module.
■ The LED Control Card contains LEDs (red, green, blue, white,
RGB) and the devices used to control them.
52 DIP Switch Interfacing: Getting Input to Your Embedded System
4.6.5 Fading RGB LED
URL: http://www.avrprojects. net/articles. php?lng=en&pg=53
The project at the above URL is done with the AVR microcontroller.
But the same can be implemented with the little modification in the
circuit diagram covered above. An RGB LED is an LED which has
three LEDs integrated in one packaging. These LEDs have the colors
red, green, and blue. With these three colors one can mix a good number
of color and fading combinations using the 8 bit PWM drive. With
8-bit PWM drive 256*256*256 combinations are possible, which leads
to 16.777 million colors, and 256 different brightness.
With the three LEDs driven with logic 1 at port pins gives white color.
The RGB LED has generally four leads, one for each color and one
for the common cathode which is connected to ground. The operating
voltages for every LED is different, viz., Red LED 2 V, Green 3.5 V,
and the Blue LED 3.5 V with each LED drawing around 20 mA current.
The timers of the microcontroller can be used to drive the particular
pattern which corresponds to fading of the LEDs. You may also use
IC555 output which is available on the kit.
4.6.6 LED Moving Font
URL: http://www.woe.onlinehome.de/e_projects.htm
Page title: World of Electronics - Electronic Projects
The project at the above URL describes a microcontroller (8051-based)
LED moving font board built up of separate modules consisting of 64
LEDs each (8x8 matrix). There is a provision of cascading the modules
according to the desired size of the font. Each module is controlled by
the LED display driver MAX7219 (or MAX7221) which can drive 64
LEDs. The display data is transferred serially to this display driver via
the pins DIN, CLK, and LOAD. The pin DOUT can be connected to
the input DIN of the following display driver, all CLK and all LOAD
pins are connected together. The modules are controlled by an 8051-
compatible microcontroller AT89C51 (LED moving font controller vari-
ant 1 or AT89C2051 (LED moving font controller variant 2 from Atmel
which provide 4 KB or 2KB flash memory on-chip.
4.7 DIP Switch Interfacing: Getting Input
to Your Embedded System
Dual in-line package (DIP) switches are electronic packages that con-
sist of a series of tiny switches. DIP switches are used to configure com-
puters and peripherals such as circuit boards and modems. They are
really useful for testing purpose. On our kit an eight input DIP switch
is provided with all its inputs available through the male connector on
the board. Any port can be connected to this DIP switch by simply
connecting the associated male connectors. This scheme is very useful
to simulate a digital input to the microcontroller.
Exploring the Capabilities of On- Chip Resources Programming
53
8
9 5
S °
5 R
2 T
+5V
Q
10 K
ResistorPack
>s.
DIP Switch
Figure 4-4 DIP switch interfacing to microcontroller
Program 4.12: DIP Switch Interfacing
Program for getting the DIP switch status and outputting the same
on LED. DIP switch status is read through port 1. LEDs are connected
to port to display the status read.
Program Source Code
"^l^ "^l^ "^l^ "^l^ "^l^ *& "^l^ "^l^ *& "^l^ *& *& "^l^ "^l^ "^l^ "^l^ "^l^ "^l^ *& "^£ *& "^£ *& "^l^ *& *& *& "^£ "^l^ *& *& "^l^ "^l^ "^£ *& *& "^£ "^l^ "^l^ "^l^ "^l^ "^l^ ^l^ *& "^r£ "^£ "^£ "^£ "^£ "^£ *& *& *&
#include <REG52.H>
void main (void)
{
char Nl; //Define the character for assignment of the
hex number.
PI = OxFF; // Define the port PI as a input port.
while(l)
{
N1=P1;
P0=N1;
}
}
Assign the value read from the port 1 to Nl.
/* display the status of the DIP switch on the
LEDs connected to port 0. */
// End of "while"
// End of "main"
54
LCD Interfacing
4.8 LCD Interfacing
LCDs are commonly used as an output interface to embedded systems
products like cell phone, data loggers and process control instruments.
Figure 4.5 shows LCD controller Hitachi 44780 that provides a relatively
simple interface between a processor and an LCD. Since the LCD inter-
facing is used in almost all our applications, a datasheet and other details
are given in annexure I. Three output pins, viz., P2.0, P2.1 and P2.2 are
used for controlling the LCD. The data is passed on to the LCD using
port 1.
The most important thing in LCD interfacing is to apply a minimum
of 450 ns wide high to low pulse to the enable pin of the LCD. This is
used to activate the latch of Hitachi 44780 to grab the data on the port
pin at that instance.
ik :
sw
+Vcc
10nF
10K
33 PI
X
XTAL ] 12 MHz
H
>
33Pf
Reset
XTALl
XTAL2
Vcc
A
T
8
9
S
5
2
Vss
I
+5V
+5V
10K
1
1K
Vcc
Vss
V
HD 44780
(16X12)
LCD
GO
"j g * D 7 D e
/|\ A /*. A A
P
P.
P
P
P„
P.
P-:
P
P
P
P
Control
Signals
Back
light
Back light
D, Do
"* — W
1
Data lines
Figure 4-5 LCD interfacing to 8051 microcontroller
Exploring the Capabilities of On- Chip Resources Programming
55
Program 4.13: Displaying String of Characters
on LCD
This program displays the string "We Thank Springer Publishers
From Authors" on the LCD. The comments are self-explanatory.
Program Source Code
#include <REG52.H>
sbit RS = P2 A 0;
sbit RW = P2 A 1;
sbit EN = P2 A 2;
/* special function register declarations
/* for the intended 8051 derivative */
Control signal RESET of the LCD connected
to pin P2.0
Write (RW) Signal pin connected to pin P2.1
Enable (EN) LCD control signal connected to
pin P2.2
int i;
void delay (void); // Delay function
void INIT(void); // Function for the commands to Initialization of
the LCD
void ENABLE (void); // Function for the commands to enable the LCD
void LINE(int); /* Function for the commands to choose the line for
displaying the characters on the LCD */
void LINE (int i)
{
if (i==l
{
RS=0;
RW=0;
Pl=0x80;
ENABLE();
RS=1;
}
else
{
RS=0;
RW=0;
Pl=0xC0;
ENABLE();
RS=1;
}
}
start of LINE function
first make the reset signal low
make RW low to give commands to the LCD
force cursor to beginning of the first line
enable the LCD
force cursor to beginning of the second line
56
LCD Interfacing
void delay () // Invoking the delay function.
{
int j;
for (j=0;j<10;j++)
{
for (i=0;i<100;i++);
}}
void ENABLE (void) // Invoking the enable function
{ EN=1; // Give high to low pulse to Enable the LCD.
delay ();
EN=0;
delay ();
}
void INIT(void)
{
// Initialization of the LCD by giving the proper
commands.
2 lines and 5*7 matrix LCD.
}
RS=0;
RW=0;
EN=0;
PI = 0x38;
ENABLE();
ENABLE();
ENABLE();
ENABLE();
PI = 0x06; //Shift cursor to left
ENABLE();
PI = OxOE;
ENABLE();
PI = 0x01;
ENABLEQ;
Display ON, Cursor Blinking
Clear display Screen.
void main (void)
{
char code dis[] = "We Thank Springer Publishers";
char code dis2[] = "From Authors"; // Array of characters
to be display.
Exploring the Capabilities of On- Chip Resources Programming 57
char *p; // Pointer to point the data in the array.
int j,x;
while(l)
{
for (x=l;x<3;x++)
{
INIT();
LINE(l); // Display on the line 1 of the LCD.
if (x==l)
{
p=&dis; // point the character address from the array "dis" where
it is stored.
}
else
{
p=&dis2; // Point the Character address from the "dis2" where it
is stored/
}
for (j=0;j>8;j++){
Pl= *p++; // Increment the pointer by 1.
ENABLE();
}
LINE(2); // Display the second array on the second line on the LCD.
}
}
}
4.9 Interrupts in Microcontrollers
Interrupts are of immense importance in any microcontroller-based
system. A peripheral such as timer/counter, A to D converter, or even a
memory or a keyboard can interrupt the microcontroller from its ongoing
sequential execution to let it know that it requires attention. This may be
due to several reasons such as timer overflowing, ADC returning data, or
the signal on an input pin changing. Generally, many standard references
compare the polling technique with the interrupt and concludes that the
interrupt is a superior technique. However, in microcontroller paradigm,
if the developer intends to use the polling technique, then he will have to
58 Interrupts in Microcontrollers
implement it in software. Ideally the peripheral can be made to set/reset
a flag, the status of which requires to be checked using a conditional
loop. But the interrupt offers a flexible and time-efficient response to
the external events with the least software overhead.
Interrupts in 8051 microcontroller are as follows:
■ Timer Overflow
■ Timer 1 Overflow
■ Reception/Transmission of Serial Character
■ External Event
■ External Event 1
4.9.1 Writing ISRs in C
Program 4.14:
This simple program illustrates the initialization sequence for the
timer, serial I/O and interrupt. A function called "serial_int" is set as the
handler for interrupt 4, which is the serial port interrupt. A character
'V is sent to the serial buffer. Observe this in the simulation window of
Keil IDE.
Program Source Code
// Serial Port Interrupt
^include <reg52.h>
^include <stdio.h>
void main (void)
{
int i;
TMOD = (TMOD & OxFO) | 0x20; // Set Timer 1
Mode 2
SCON = 0x50; // Serial Communi-
cation Mode 1
EA = 1; // Enable Global
Interrupt Bit
ES = 1; // Enable Serial Port
Interrupts
Exploring the Capabilities of On- Chip Resources Programming 59
TH1 = OxFD; // Load Timer 1 Baud Rate
TR1 = 1; //Set Timer 1 Run control
bit
while (1)
{
SBUF = 'V; //Send V continuously on
//Serial Port
for(i=0;i<=10;i++); /* Delay to avoid trans-
mission overlapping */
}
}
// Serial Port Interrupt Service Routine.
void timerO JSR (void) interrupt 4
{
TI = 0; //Clear transmission
interrupt flag
********** J*********************************************
Program 4.15:
This program is modification of the Program 4.14. Unlike the inter-
rupt technique used in Program 4.14, here the interrupt flag is polled
continuously. Observe the transmission of 'v' in simulator window.
Program Source Code
Serial port Interrupt Programming
#include<REG52.H>
void main()
{
TMOD=0x20; // Timer 1 Mode 2
TH1=0XFD; // Baud rate = 9600 for 11.0592
60
Interrupts in Microcontrollers
MHz XTAL
TL1=0XFD;
}
SCON=0X50;
TR1 = 1;
TI = 0;
while(l)
{
SBUF = V;
while(!TI);
TI = 0;
}
//Serial Communication
mode 1
// Start Timer 1
// Clear Transmit Interrupt
flag
// Send V continuously on
Serial port
Check TI flag till it is zero
// Clear Transmit Interrupt
flag
Program 4.16: Implementation of Minutes Counter
This program implements a seconds counter on the serial seven-
segment LED. Timer is used for the generation of delay of a minute.
With elapsing of the delay routine the count is incremented and dis-
played on the serial seven-segment LED. The 4 seven- segment display is
serially connected. Pins P3.7 is used for clock generation and the data
is transferred serially over the pin P3.6.
Program Source Code
#include<REG52.H>
void display (char a);
void clear(void);
void INIT (void);
void delay (void);
unsigned int count, milliseconds; // Unsigned Integers for the count.
sbit dat=P3 A 6; // Set the pin to Sending the data bits over the pin
P3.6
sbit clk=P3 A 7; // Set the pin to send elk
Exploring the Capabilities of On- Chip Resources Programming 61
unsigned int delay 1;
unsigned char s[10]= {0xc0,0xf9,0xa4,0xb0,0x99,0x92,0x82,0xd8,0x80,
0x90};
void delay(void) // Invoking the Delay routine
{
int c,d;
for(c=0;c<2;c++)
{for(d=0;d<2000;d++);
}}....
void INIT (void) // Invoking the function to start the timer
{
TMOD=0X01;
TF0=0; /* Timer overflow flag reset first, Start the timer and
set the interrupt when timer overflows */
TR0=0;
delayl=50000;
delay 1=~ delay 1; // Complement the delay count
TL0=delayl%256; // Count loaded in the Timer lower byte.
TH0=delay 1/256; // Load the higher byte of timer
TR0=1; // Run the timer
ET0=1;
EA=1; // Global interrupt bit
IP=0x00;
}
void clear (void) /* Invoking the function to clear the display */
{
int j;
dat=l;
for(j=0;j<32;j++)
{
clk=0; // Sending the pulse to clear the display
clk=l;clk=0;
}}
void display(char a) // Display the numbers on the seven-segment
LEDs
{
unsigned char mask;
int y;
mask=0x80; // Mask the higher digit
62
Interrupts in Microcontrollers
for(y=0;y<8;y++
{
if(a&mask)
dat=l;
else
dat=0;
clk=0;
clk=l;clk=0;
mask=mask> > 1 ;
/* If the unit digit goes overflow then switch the
upper digit. */
// Invoking the main function
void main(void)
{
unsigned char m,n;
clear ();
count=0; milliseconds=0;
INIT(); // Initializing the timer
do
{
clear ();
n=count%10;
m= ( (count/10) % 10);
display(s[m]); // Display the count at higher digit position
display(s[n]); // Display the count on the lower digit position
delay ();
}
while (count < 60);
TR0=0;
while (1);
}
void) interrupt 1
{
TR0=0; TF0=0;
delayl=50000;
delay f=~delayf;
TL0=delayl%256;
TH0=delayl/256;
Function for the interrupt routine when timer
overflows
Reset the timer and the timer flag
Exploring the Capabilities of On- Chip Resources Programming 63
milliseconds++; // Increment the millisecond count by one
if (milliseconds == 20)
{
count ++; // Increment the count
milliseconds=0;
}
TR0=1; // Run the timer
4.9.2 A Word about Interrupt Latency
Interrupt latency is the time between the generation of an interrupt
by a device and the servicing of the device which generated the interrupt.
In other words it is the time taken to service the interrupt or the longest
time between when the interrupt occurs and when the microcontroller
suspends the current processing context.
Interrupt latency is an important issue in microcontroller-based sys-
tem design for several reasons. Microcontroller-based system with a sin-
gle interrupt will execute correctly (as per the intended logic of the
developer) provided ISR execution time is smaller than the frequency
of the interrupt. One of the most important issues in microcontroller-
based embedded systems is the power consumption, since the system
aims at remote installation with long battery life. From the low power
consumption point of view, the crystal frequency should be at the low-
est end of the permissible limit. This value is ultimately decided by
the interrupt latency (generally the standard values should be adopted
to give prescribed baud rates in serial communication). Improving the
interrupt latency results into lowering down the throughput and increas-
ing the processor utilization. On the other hand, reducing the processor
utilization may increase interrupt latency but may decrease the overall
throughput.
Program 4.17: Estimating Interrupt Latency
Program Source Code
^include <REG52.H> /* special function register declarations */
/* for the intended 8051 derivative */
sbit RS = P2 A 0;
sbit RW = P2 A 1;
64
Interrupts in Microcontrollers
— TDOAo.
sbit EN = P2 A 2;
sbit interruptl = P3 A 3;
sbit IN =P2 A 3;
void delay (int);
void INIT(void);
void ENABLE(void);
void LINE(int);
int ONTIME(int);
// External interrupt
void LINE (int i)
{
if (i==l)
{
RS=0;
RW=0;
Pl=0x80;
ENABLE();
RS=1;
}
else
{
RS=0;
RW=0;
Pl=0xC0;
ENABLE();
RS=1;
}
}
void delay ()
{
int i,j;
for (j=0;j<10;j++){
for (i=0;i<100;i++);
}}
void ENABLE (void)
{
EN=1;
delay ();
Enabling the Line function
Invoking the Enable function for the LCD
Exploring the Capabilities of On- Chip Resources Programming 65
EN=0;
delay ();
}
void INIT(void) // Initialization of the LCD by giving the proper
commands
{
RS=0;
RW=0;
EN=0;
PI = 0x38; // 2 lines and 5*7 matrix LCD
ENABLEO
ENABLE()
ENABLE()
ENABLE()
PI = 0x06; // Shift cursor to left
ENABLEO;
PI = OxOE; // Display ON, Cursor Blinking
ENABLE();
PI = 0x01; // Clear display Screen
ENABLE();
}
int ONTIME() // Invoking the ONTIME function
{
TMOD=0x01; // Intialize as 16 bit timer(mode l)(Timer 1)
TL0=0x00;
TH0=0x00;
TR0=1; // start the timer
IN=1; /*input to 8052 from 555 osc*/
while(IN);
while(!IN);
while(IN);
TR0=0; // stop the timer
return((TH0*256)+TL0); // return the ISR Execution count
}
void main (void){
int latency, unit, tens, hundred, thousand,
66 Interrupts in Microcontrollers
tenthou, unitl, tensl, hundredl, thousand 1, tenthoul;
char code dis[] = "ISR Execution Time=";
char code dis2[] = "Interupt Latency=";
char *p;
int i,j;
while(l)
{
TMOD=0x01; // Initialize the timer to count the total program
execution time
THl=0x00;
TLl=0x00;
TR1=1; // Start the timer 1
if(interruptl==l)
{
i = ONTIME();
unit = (i%10);
tens = (i/10)%10;
hundred = (i/100)%10;
thousand = (i/1000)%10;
tenthou = (i/10000)%10;
unit = unit + 0x30; // Sending the ASCII data to the LCD
tens = tens + 0x30;
hundred = hundred + 0x30;
thousand= thousand + 0x30;
tenthou = tenthou + 0x30;
INIT();
LINE(l);
p=&dis;
for (j=0;j<8;j++){
Pl= *p++;
ENABLE();
}
LINE(2);
Pl=tenthou;
ENABLE();
Pl=thousand;
ENABLE();
Pl=hundred;
ENABLE();
Exploring the Capabilities of On- Chip Resources Programming 67
Pl=tens;
ENABLE();
Pl=unit;
ENABLE();
}
else
{
p=&dis2;
for (j=0;j<8;j++){
Pl= *p++; // Pointer to point the data from the array
ENABLE(); // Enabling the LCD
}
LINE (2); // Display the content on the second line of the LCD
TR1=0; // stop the timer 2
latency=(((THl-TH0)*256)-(TLl-TL0)); //Timer count is subtra-
cted from timer 1
unitl = (latency % 10);
tensl = (latency/10)%10;
hundredl = (latency/100)%10;
thousandl = (latency/1000)%10;
tenthoul = (latency/10000)%10;
unitl = unitl + 0x30;
tensl = tensl + 0x30;
hundredl = hundredl + 0x30;
thousand 1= thousandl + 0x30;
tenthoul = tenthoul + 0x30;
LINE(2);
Pl=tenthou; // display the latency
ENABLE();
Pl=thousand;
ENABLE();
Pl=hundred;
ENABLE();
Pl=tens;
ENABLE();
Pl=unit;
ENABLE();
}
}
}
Chapter 5
Hyperterminal-Based Control
5.1 Hyperterminal
Hyper Terminal is a terminal emulator program that runs in MS
Windows. It offers a text-based command prompt interface on a
remote device. The remote device is a serial device, and it could be
a router, connected directly to the PC's serial port OR a network
device. Hyper Terminal is generally used for the local serial interface for
communications or the network. In the case of the network, HyperTer-
minal is simply using the telnet protocol. In order to communicate with
the device, the HyperTerminal must be configured on the right COM
port (either COM1 or COM2) and at appropriate baud rate (most of
the time 9600 for applications written here).
Having designed to emulate various types of text terminal configurable
to make a over a serial port the serial parameters to be selected are:
■ Baud rate
■ Parity (odd, even, none)
■ Stop bits
■ Flow control
5.2 Packet-based Control Scheme
The beauty of the programs covered in this section is that they present
an insight with regard to the new protocol development. The remote
host, i.e., microcontroller board connected to COM1, has various com-
mand blocks which will be invoked based on the parameters passed from
the HyperTerminal. The command blocks are packed and a particu-
lar packet corresponding to the desired control sequence that is made
alive as soon as the associated command parameter is received from the
HyperTerminal.
69
J.S. Parab et al. (eds.), Exploring C for Microcontrollers, 69-83.
© 2007 Springer.
70 Mechanism and Lots of Possibilities
Two things are required to keep in mind in these applications:
maintaining the compatibility of PC serial port to microcontroller;
and selection of proper baud rate. A standard serial interfacing for PC,
RS232C, requires negative logic, i.e., logic '1' is — 3 V to —12 V and logic
'0' is +3V to +12 V. In order to convert a TTL logic, say, TxD and
RxD pins of the microcontroller chips, a converter chip is required. A
MAX232 chip is a very popular chip used in the circuit boards for all the
applications covered in this chapter. It provides 2-channel RS232C port
and requires external lOuF capacitors. The polarity of the capacitor is
crucial which the user must note. Another possibility in lieu of MAX232
is DS275, which does not require an external capacitor.
5.3 Mechanism and Lots of Possibilities
The mechanism of packet-based interface works as follows. The num-
ber of control possibilities are listed in case of each control module and
categorized in terms of packets. For instance, in case of the LED inter-
face board, various display sequences are defined as packets. In case of
stepper motor-based interface the packet definitions include the clock-
wise, anticlockwise rotations in the first instance and step size as the
secondary instance, both the things defined together. As per the firing
of the commands from the Hyper Terminal the firmware residing in the
microcontroller flash will invoke the appropriate control action.
The following simple steps will help you to configure the
Hyper Terminal.
1. Open the Hyper Terminal, by clicking
Start >Programs>Accessories>Communications>Hyper Terminal.
2. This will prompt you to create a new connection. The new connec-
tion can also be created by clicking File > New Connection. Enter
a name for the connection and click OK.
3. Select the serial port where the device is connected to the PC
(COM1 in our case). Click OK.
4. Enter the following configuration for the connection:
Bits per second 9600
Data bits 8
Parity None
Stop bit 1
Flow control None
Click OK.
Hyperterminal- Based Control
71
5. After clicking OK or apply all, the above configuration will be
loaded and the commands can be entered at the command prompt.
This HyperTerminal-based interface offers great possibilities from con-
trol point of view. With little modification in the hardware it is possible
to go for web enabling of the embedded products by adding an Ethernet-
based interface. Internet-based data logging and control, microcontroller-
based server, and client applications are possible with optimized usage
of resources due to packet methodology.
5.4
Application 1: Packet-based Interface
for LEDs
The circuit diagram of the packet-based LED interface is as shown in
Figure 5.1. The commands to be emulated from the Hyper Terminal and
the corresponding control action is given in the program source code.
+5V
33041
330O J*x
W-
»»
ft
33PF
12MHz QH XTAL
-3H
+5V
" 33PF
P
P
R.D
I'D
AT89S52
XTAL1
XTAL2
GND
T
K>nf4_
IO M f»
+5V
10(.if
ne
vcc
T IN
V,
R,IN
R,OUT £j
r . N T,0UT
<
Or S T s OUT
C,+
R a IN
V-
X
I
DB9
CONNECTOR
Figure 5. 1 Circuit diagram of packet-based interface for LED
Program Source Code
/* Displaying different LED sequence pattern based on the packet
received */
#include<REG52.h>
72
Application 1: Packet-based Interface for LEDs
unsigned char led;
int interpret;
char packet [4];
char index;
void init(void);
void delay (int m);
void init()
{
TMOD=0X20;
THl=0xFD;
SCON=0x50;
TR1=1;
}
void main(void)
{
int k=0;
char i;
init();
ES=1;
EA=1;
led=0xff;
for (i=0;i<4;i++){
packet [i]=0;
}
index=0;
interpret=0;
while(l)
{
{
P0= led;
delay (1000);
}
}}
void delay (int m)
{
int z;
z=m:
select baud rate 9600 :
start timer
Global interrupt bit enabled
Function for the Delay.
Hyperterminal-Based Control 73
while (m>0)
{ m ;}
}
void serialisr() interrupt 4
{
unsigned char y;
char i;
RI=0;
y=SBUF; // write the data in srial buffer.
TI=0;
SBUF=y; // read the data from serial buffer.
while (!TI); // Check the flag
TI=0;
packet [index] =y ;
index++;
if (y==V)
{
interpret =1;
index = 0;
}
else interpret = 0;
if (interpret==l)
{
switch(packet [0] )
{
case 'A':
led=0x55; // 01010101
break;
case 'B':
led=0x33;
break;
case 'C:
led=0x55;
delay(lOO);
led=0x33;
break;
case 'D':
led=0x00;
74 Application 2: Packet-based Interface for Stepper Motor Control
delay(lOO);
led=0x02;
delay(lOO);
led=8;
delay (100);
led=16;
delay(lOO);
led=16;
delay (100);
led=32;
delay (100);
led=64;
delay (100);
led=256;
delay (100);
break;
}
for (i=0;i<4;i++)
{
packet [i]=0;
}
interpret=0;
}
}
5.5 Application 2: Packet-based Interface
for Stepper Motor Control
The circuit diagram of the packet-based stepper motor interface is as
shown in Figure 5.2. The commands to be emulated from the Hyper-
Terminal and the corresponding control action are given in the pro-
gram source code. The interface is based on UN2003 driver popularly
used for many stepper motor control applications. It is a 7-bit, 50 V
500 mA TTL-input NPN Darlington driver. The drivers does not need
power supply; the VDD pin is the common cathode of the seven in-
tegrated protection diodes. The details are covered in may web-based
resources [35].
Hyperterminal- Based Control
75
Figure 5.2 Circuit diagram of stepper motor interface
Program Source Code
#include<REG52.h>
unsigned char mot [4] = {0x0a, 0x06, 0x05, 0x09};
unsigned char run, clkwise;
int interpret, mode, count;
char packet [5]; /*p[0] is control char*/
char index; /*others may contain data last must contain end char,
i.e., 'z' 7
void init(void);
void delay (int m);
void init()
{
TMOD=0x20;
THl=0xFD; /*select baud rate 9600*/
SCON=0x50;
TR1=1; /* start timer*/
}
76 Application 2: Packet-based Interface for Stepper Motor Control
void main (void)
{
int k=0;
char i;
init(); ES=1; EA=1;
run=l;
clkwise = 1;
for (i=0;i<5;i++){
packet [i]=0;
}
index=0;
interpret=0;
while(l)
{
while(mode==0){ /* continues rotation*/
while(run==l)
{if(clkwise==l){
for (i=0;i<4 ; i++) /* clkwise dir*/
{ P0= mot [i];
delay (1000);
}}
else
{for (i=3;i>=0 ; i ) /*anticlkwise dir*/
{ P0= mot [i];
delay (1000);
}
}
}
}
}
while(mode==l) /*number of step's given by user*/
{
while((run==l)&&(count>0))
{
if(clkwise==l){
for ( i=0;i<4 ; i++)
{
P0= mot [i];
delay (1000);
}
}
Hyperterminal- Based Control
77
else
{
}
}
for ( i=3;i>=0 ; i )
{
P0= mot [i];
delay (1000);
}
}
count ;
}
void delay (int m)
{ int z;
z=m;
while (m>0)
{ m ;}
}
void serialisr() interrupt 4
{
unsigned char y;
char i;
RI=0;
y=SBUF;
TI=0; SBUF=y; while (!TI);TI=0;
packet [index] =y ;
index++;
if (y=='Z') {
interpret =1; /* indicates end of packet :
index = 0;
}
else interpret = 0;
if (interpret==l)
{
switch(packet [0] )
{
case 'S':
run=0;
break;
contents of buffer
* /
in y
/*similtaneusly
display*/
78 Application 3: Home Automation from PC HyperTerminal
case 'R':
run=l;
break;
case 'A':
clkwise=0;
break;
case 'C:
clkwise=l;
break;
case 'D':
if (packet[l]=='0')
mode=0;
break;
case 'E':
if (packet[l]=='l')
mode=l;
break;
case 'F': /*variable size packet*/
count=(packet[3]-0x30)+((packet[2]-0x30)*10)+((packet[l]-
0x30)*100);
break; /*packet[3]=units */
}
for (i=0;i<5;i++){
packet [i]=0;
}
interpret=0;
}
5.6 Application 3: Home Automation from PC
HyperTerminal
Home Automation from PC Terminal
With the deep penetration of PCs in today's modern homes, the
trend of PC- based home automation is growing. There are different
home automation systems that consist of controller and device control-
ling modules (relays, light dimmers, etc.). New protocols such as X10
system that communicates through mains wiring is gaining popularity.
Hyperterminal-B ased Control
79
89S52
Microcontroller
Multiple
RS- 232
Interface
Figure 5. 3 Block schematic of the hyper terminal based home automation system
33Pt
I
|~|l2MHz
• , 33Pf
o o
Vcc
XTAL1
XTAL2
CND
AT 89S 52
P.. P.. P»' P - P «
O o
o o
o
OB 9
ComMdn
10|iF
u q fcr 2 t
> si& I
i- or
MAX 232
* i + i
o > o o o >
r
10uF"T-
~\<-
1
lO^F
W
u
u
MOC3030
'Sat
s
<
MOC man
V lr (230V)
o o
F
P
p
PC
p»
OVEN
p
VtfesNng
Mactvne
Pa
Dryer
CD PLAYER
=1
V^ (230V)
App'iance
Cirrutf Diagram ot Horn* Airtwruton from PC
Figure 5.4 Circuit diagram
80 Application 3: Home Automation from PC HyperTerminal
However, any embedded developer would definitely love to write his own
protocol for the home automation system. Here is the one which com-
municates with the 89S52-based microcontroller board through Hyper-
Terminal of PC. Again the packet-based methodology has been used.
The drivers for various appliance control such as lights, garage door,
audio system, TV, etc., resides in the microcontroller flash and are
invoked based on the command character passed on from the Hyper-
Terminal. The microcontroller-based interfacing board comprises opto-
isolator MOC3030 which has built-in zero crossing detection.
Program Source Code
^i^ "^c "^z *& "^c "^z *& "^c *& *& *& *& *& "^z *& "£? *& *& *& "^z *& "^z "^z *& *& ^i^ *& *& "£? "£? "£? "£? "£? "^z "^c "£? "^z *& "£? *& *& *& *& *& "^z *& "£? *& *& "^z *& "^c "^z *& "^c "^z *& *& *& *& *&
#include<REG52.h>
unsigned char light;
int interpret;
/* The pins of the port are connected to power line of various
home appliances through the control circuitry to control them by
on/off the power supply. */
sbit lightl=P0 A 0; // Pin connected to the control circuit of the
Light 1.
sbit light2=P0 A l;
sbit TV=P0 A 2; // Pin connected to control circuit of power supply
of TV.
sbit PC = P0 A 3;
sbit oven = P0 A 4;
sbit washing = P0 A 5;
sbit coller = P0 A 6;
sbit CD = P0 A 7;
char packet [4];
char index;
void init(void);
void delay (int m);
void init()
{
TMOD=0X20;
THl=0xFD; /*select baud rate 9600*/
SCON=0x50;
Hyperterminal-Based Control 81
TR1=1; /* start timer*/
}
void main (void)
{
int k=0;
char i;
init(); ES=1; EA=1;
for (i=0;i<4;i++){
packet [i]=0;
}
index=0;
interpret =0;
while(l)
{
{
P0=lightl;
delay(lOOO);
}
}}
void delay (int m)
{ int z;
z=m;
while ( m >0)
{ m ;}
}
void serialisr() interrupt 4
{
unsigned char y;
char i;
RI=0;
y=SBUF;
TI=0; SBUF=y; while (!TI);TI=0;
packet [index] =y;
index++;
if (y=='z') {interpret =1; index = 0;}
else interpret = 0;
82
Application 3: Home Automation from PC HyperTerminal
if (interpret==l)
{
switch (packet [0])
{
case 'A':
lightl=l;
break;
case 'B':
lightl=0;
break;
case 'C:
light2=l;
break;
case 'D':
light2=0;
Washing machine
break;
case 'E':
TV=1;
break;
case C F':
TV=0;
break;
case 'G':
PC=1;
break;
case 'H':
PC=0;
break;
case T:
oven= 1 ;
break;
case 'J':
oven=0;
break;
case 'K':
washing=l;
break;
case 'L':
switch on the bulbl
// switch off the bulbl
// switch on the bulb2
switch off the bulb2// // switch on
// switch on the TV
// switch off The TV
// switch on PC
// switch off the PC
switch on oven
// switch off oven
// switch on the washing machine
Hyperterminal- Based Control
83
washing=0;
break;
case 'M':
coller=l;
break;
case 'N':
coller=0;
break;
case 'O':
CD=1;
break;
case 'P':
CD=0;
break;
}
switch off the washing machine
// switch on cooler
// switch off the cooler
switch on CD player
switch off CD player
for (i=0;i<8;i++){
packet [i]=0;
}
interpret=0;
}}
Chapter 6
Embedding Microcontroller in Routine
Applications
This chapter illustrates how embedding microcontroller in day-to-day
applications altogether changes the throughput of the product.
6.1 Application 1: Podium Timer
The podium timer is designed for giving the indication of timeout for
a series of timed speeches. The 4x4 hex keyboard enables the user to
set the time and start the timer. Once the timer is ON, it constantly
indicates the time on the LCD. Before 3 minutes (which is also program-
mable) of actual timeout, it gives an indication by means of short beep.
As soon as the time set is elapsed, the unit enables the buzzer indicating
the timeout.
Program Source Code
#include <REG52.H>
sbit RS = P2 A 0;
sbit RW = P2 A 1;
sbit EL = P2 A 2;
sbit buzz = P2 A 3;
sbit Rl = P3 A 0:
sbit R2 = P3 A 1
sbit R3 = P3 A 2:
sbit R4 = P3 A 3:
sbit CI = P3 A 4:
sbit C2 = P3 A 5:
sbit C3 = P3 A 6:
/* special function register declarations
for the intended 8051 derivative */
85
J.S. Parab et al. (eds.), Exploring C for Microcontrollers, 85-122.
© 2007 Springer.
86 Application 1: Podium Timer
sbit C4 = P3 A 7;
void Delay(int);
void INIT(void);
void ENABLE(void);
void LINE(int);
int keyb(void);
void settime(void);
void starttimer(void);
void check_timeout(int);
int settimel=10;
void settime(void)
{
int ten_pos=0, unit_pos=0;
while(!(ten_pos=keyb()));
while(!(unit_pos=keyb()));
Pl=(((ten_pos))+0x30);
ENABLE();
Pl=((unit.pos)+0x30);
ENABLE();
Delay (2000);
settimel= ten_pos*10 + unit.pos;
}
void starttimer()
{
int set_temp= settime;
check_timeout(3); //check for the warning timeout default 3 min before
end time
check_timeout(set_temp) ;
set _temp-;
Pl=(((set_temp)/10)+0x30);
ENABLEi
Pl=((set_temp/10)%10+0x30);
ENABLE();
Embedding Microcontroller in Routine Applications 87
Delay (2000);
I
void check_timeout(g)
{
if(g == 3)
{
buzz=l;
Delay (100);
buzz=0;
}
if (g == 0)
buzz=l;
Delay (400);
buzz=0;
}
void main (void)
{
char test [] = "Podium timer" ;
char code set_msg[]="l-> set time";
char code start_msg[]="2-> start timer";
char *p;
hit j;
INiT();
LINE(l);
p=&test;
for(j=0;j<17;j++)
{
if(j==0)LINE(l);
if(j==8)LINE(2);
Pl= *p+ + ;
ENABLE();
Delay (200);
}
while(l){
RS = 1;
p=&set_msg;
for(j=0;j<17;j++)
{
88 Application 1: Podium Timer
if(j==0)LINE(l);
if(j==8)LINE(2);
Pl= *p++;
ENABLE();
Delay (200);
}
RS= 1;
p=&start_msg;
for(j=0;j<17;j++)
{
if(j==0)LINE(l);
if(j==8)LINE(2);
Pl= *p++;
ENABLE();
Delay (200);
}
j=0;
j=keyb();
if(j>0);
if(j==l){
settime();
}
if(j==2){
starttimer();
}
}
}
void Delay(int k)
{
int i,j;
for (j=0;j<k+l;j++){
for (i=0;i<100;i++);
}}
void ENABLE (void)
{
EL=1;
Delay(l);
Embedding Microcontroller in Routine Applications
89
EL=0;
Delay(l);
}
void LINE(int i){
if (i==l) {
RS=0;
RW=0;
Pl=0x80;
ENABLE();
RS=1;
}
else
{
RS=0;
RW=0;
Pl=0xC0;
ENABLE();
RS=1;
}
}
void INIT(void)
{
}
RS=0;
RW=0;
EL=0;
PI = 0x38;
ENABLE()
ENABLEQ
ENABLEQ
ENABLEQ
PI = 0x06;
ENABLE();
PI = OxOE;
ENABLE();
PI = 0x01;
ENABLEQ;
Initialization of the LCD by giving the proper
commands.
// 2 lines and 5*7 matrix LCD.
//Shift cursor to left
Display ON, Cursor Blinking
Clear display Screen.
int keyb(void){
int key=0;
Cl=l;
90
Application 2: Front Desk Notifier
C2=1;C3=1;C4=1;R1=0;R2=1;R3=1;R4=1;
if (C1==0) key = 1
if (C2==0) key = 2
if (C3==0) key = 3
if (C4==0) key = 4
return(key);
}
+5V
33PF
12MHz XTAL
ih
.. 33PF
Vcc
XTAL1
XTAL 2
CM
00
GND
T
P»
P
P,
P.
+5V
10K
EN
R/W
RS
HD 44780
16X2
D, LCD
Do
1K
KEY PAD
4X4
MATRIX
Buzzer
BC547
Figure 6. 1 Circuit diagram of the podium timer
6.2 Application 2: Front Desk Notifier
The project aims to build an automated system that will alert the
food assistance staff that a customer has arrived for service. It can also
be used for a housewife who wants to know if someone has arrived at the
gate. An IR transceiver pair has been used for detecting the presence
of the person at the front desk. The program polls the port pins and
Embedding Microcontroller in Routine Applications
91
33PF
12MHz □ XTAL
33PF
V
+5v
Vcc
XTAL1
XTAL2
Pi,
P1.0
"2.2
P
2.Q
AT 89S52
GND
2.5
T
Vcc
D7
V
a
V
M
DO
LCD
EN
R/W
RS
1K
+5v
10K
*
Buzzer
BC547
Figure 6.2 Circuit diagram of front desk notifier system
displays a message on the LCD that "Someone is arrived" as well as
activates a buzzer. The system is also ideal for a bank cashier.
Program Source Code
^include <REG52.H> /*special function register declarations 1
/* for the intended 8051 derivative */
sbit RS = P2 A 0;
sbit RW = P2 A 1;
sbit EN = P2 A 2;
sbit IN= P2 A 4;
sbit Buzz=P2 A 5;
void delay (int);
void INIT(void);
void ENABLE(void);
voidLINE(int);
input from the sensor present at gate :
output indication to housewife*/
/* Stop Exection with Serial Intr.
92 Application 2: Front Desk Notifier
void LINE(int i){
if (i==l) {
RS=0;
RW=0;
PI =0x80;
ENABLE();
RS=1;
}
else
{
RS=0;
RW=0;
Pl=0xC0;
ENABLE();
RS=1;
}
}
void delay ()
{
int i,j;
for (j=0;j<10;j++){
for (i=0;i<100;i++);
}}
void ENABLE(void)
{
EN=1;
delay();
EN=0;
delay ();
}
void INIT(void) // Initialization of the LCD by giving the proper
commands.
{
RS=0;
RW=0;
EN=0;
PI = 0x38; // 2 lines and 5*7 matrix LCD.
Embedding Microcontroller in Routine Applications
93
}
ENABLE()
ENABLE()
ENABLE()
ENABLEQ
PI = 0x06; //Shift cursor to left
ENABLE();
PI = OxOE; // Display ON, Cursor Blinking
ENABLE();
PI = 0x01; // Clear display Screen.
ENABLEQ;
void main (void){
char code array [] = "Some is there on the gate";
char code arrayl[]="No one is there on the gate";
int b,j;
Buzz=0;
while(l)
INIT();
LINE (1);
{
if( IN==1)
{
Buzz=l;
some one is there if in = 1
// switch on the buzzer to indicate some
one is there on gate
for (b=0;b<30;b++
{
if (b==8)
LINE(2);
Pl=array[b];
ENABLE();
}
RS=0;
Pl=0x01;
ENABLE();
RS=1;
LINE(l);
for (b=16;b<33;b++)
{
if (b==24)
94
Application 3: Cafeteria Food Alert/ Microcontroller-based Menu Card
LINE(2);
Pl=arrayl[b];
ENABLE();
}
}
else
{
for (b=0;b<30;b++)
{
if (b==8)
LINE(2);
Pl=arrayl[b];
ENABLE();
}
RS=0;
Pl=0x01;
ENABLE();
RS=1;
LINE(l);
for (b=16;b<33;b++)
{
if (b==24)
LINE(2);
Pl=arrayl[b];
ENABLE();
}
}
}
}
display no one there on gate
6.3
Application 3: Cafeteria Food
Alert/Microcontroller-based Menu Card
This economic unit is an ideal solution for small hotels. The customer
can place an order of the item by pressing a key corresponding to the
item he or she would like to order. The other half of the unit is the
LCD display which is kept in the kitchen. The item will be displayed on
the LCD and subsequently served to the customer. An interrupt will be
invoked in case the customer wants bill or to place an item which is not
there in menu or in case of any other events.
Embedding Microcontroller in Routine Applications
95
33PF
II—
12MHz[ fAL
33 PF
£
+5v
_L
HD 44780
Vcc
XTAL1
A
T
8
9
XTAL2 S
5
2
GND
'o.o
•2 2
P 2 ,
P,,
P,o
Po,
Control
Signals
Data
lines
10K
10K
KEY PAD
(4X4)
V
EN
R/W
RS
Vcc
D7 LCD
(16X2)
DO
1K
?
5V
10K
+5V
-C BC547
Buzzer
Figure 6. 3 Circuit diagram of microcontroller-based menu card
Program Source Code
*^r£ *& ~^£ *& *& *& "^l^ "^l^ "^£ *& *& *& *& *& "^£ "^C "^£ *& "^£ "^r£ *& "^£ "^l^ "^l^ *& "^l^ *& *& *& "^£ *& "^l^ "^l^ *& *& "^l^ "^£ "^£ "^l^ *& *& "^£ *& *& "^r£ "^£ "^£ "^£ *& "^£ *& *& "^£ *& "^£ *& "^l^
^include <REG52.H>
^include <stdio.h>
/* for the intended 8051 derivative
special function register declarations
sbit RS :
sbit RW
sbit EL :
sbit BU
sbit Rl =
sbit R2 =
sbit R3 =
sbit R4 =
P2 A 0;
: P2 A 1;
P2 A 2;
P2 A 4;
P0 A
P0 A 1
P0 A 2
P0 A 3
sbit CI = P0 A 4;
sbit C2 = P0 A 5;
96 Application 3: Cafeteria Food Alert/ Microcontroller-based Menu Card
sbit C3 = P0 A 6;
sbit C4 = P0 A 7;
void delay(int); /* Stop Execution with Serial Intr. */
void INIT(void);
void ENABLE (void);
void LINE(int);
int keyb(void);
void LINE (int i){
if (i==l) {
RS=0;
RW=0;
Pl=0x80;
ENABLE
RS=1;
}
else
{
RS=0;
RW=0;
Pl=0xC0;
ENABLE
RS=1;
}
}
void delay (int k)
{
int i,j;
for (j=0;j<k+l;j++){
for (i=0;i<100;i++);
}}
void ENABLE (void)
{
EL=1;
delay(l);
EL=0;
delay(l);
}
Embedding Microcontroller in Routine Applications
97
2 lines and 5*7 matrix LCD.
void INIT(void) // Initialization of the LCD by giving the proper
commands.
{
RS=0;
RW=0;
EL=0;
PI = 0x38;
ENABLE()
ENABLE()
ENABLE()
ENABLE()
PI = 0x06;
ENABLE();
PI = OxOE;
ENABLE();
PI = 0x01;
ENABLE();
}
int keyb(void){
int key=0;
Cl=l
C2=l
C3=l
C4=l
//Shift cursor to left
Display ON, Cursor Blinking
Clear display Screen.
R1=0:
R2=l
R3=l
R4=l
if (CI:
if (C2 =
if (C3=
if (C4=
Rl=l
R2=0:
R3=l
R4=l
0) key
0) key
0) key
=0) key
1
2:
3:
4:
98
Application 3: Cafeteria Food Alert/ Microcontroller-based Menu Card
if (C1==0) key = 5
if (C2==0) key = 6
if (C3==0) key = 7
if (C4==0) key = 8
Rl=l;
R2=l;
R3=0;
R4=l;
if (C1==0) key = 9;
if (C2==0) key = 10
if (C3==0) key = 11
if (C4==0) key = 12
Rl=l;
R2=l;
R3=l;
R4=0;
if (C1==0) key = 13
if (C2==0) key = 14
if (C3==0) key = 15
if (C4==0) key = 16
return(key);
}
void main(void) {
char arrayl[] = "tea";
char array2 [] = "wheat" ;
char array3 [] = "rice" ;
char array4 [] = "dal" ;
char array 5 [] = "jaggery" ;
char array6 [] = "coffee" ;
char array7[] = "item is not there in menu";
char array8[] = "Get the bill";
char *p;
int j,i;
INITQ;
LINE(l);
j=0;
Embedding Microcontroller in Routine Applications 99
while(l){
j=0;
j = keyb();
if(j==l){
for (i=0;i<8;i++){
p=&arrayl;
Pl= *p+ + ;
ENABLE();
}}
if(j==2){
for (i=0;i<8;i++){
p=&array2;
Pl= *p+ + ;
ENABLE();
}}
if(j==3){
for (i=0;i<8;i++){
p=&array3;
Pl= *p++;
ENABLE();
}}
if(j==4){
for (i=0;i<8;i++){
p=&array4;
Pl= *p++;
ENABLE();
}}
if(j==5){
for (i=0;i<8;i++){
p=&array5;
Pl= *p++;
ENABLE();
}}
if(j==6){
for (i=0;i<8;i++){
p=&array6;
Pl= *p+ + ;
ENABLEi
}}
100 Application 4- Chimney Sentinel
if(j==7){
for (i=0;i<8;i++){
p=&array7;
Pl= *p++;
ENABLE();
}}
if(j==8){
for (i=0;i<8;i++){
p=&array8;
Pl= *p++;
ENABLE();
}}
delay (400);
ENABLE();
delay (400);
}
6.4 Application 4: Chimney Sentinel
The reports of incidents of fire due to wood-burning appliances are
reported every year. This causes lots of damage to the human being as
well as property. The device consists of a probe comprising a tempera-
ture sensor LM35 inserted in the chimney. This is in turn interfaced to
ADC0808 and AT89S52 microcontroller-based monitoring unit. When
the temperature rises the preset value set by the user, a fire is detected,
and the unit sounds an alarm. There is also a provision to display the
temperature on the LCD.
Program Source Code
^include <REG52.H> /* special function register declarations */
^include <stdio.h>
/* for the intended 8051 derivative */
sbit RS = P2 A 0;
sbit RW = P2 A 1;
sbit EL = P2 A 2:
Embedding Microcontroller in Routine Applications 101
sbit BUZZ=P2 A 3;
sbit SOC= P2 A 4;
sbit a =P2 A 5;
sbit b = P2 A 6;
sbit c =P2 A 7;
void delay (int);
void INIT(void);
void ENABLE (void);
void LINE(int);
void LINE (int i){
if(i==l){
RS=0;
RW=0;
P0=0x80;
ENABLE();
RS=1;
}
else
{
RS=0;
RW=0;
P0=0xC0;
ENABLE();
RS=1;
}
}
void delay (int k)
{
int i,j;
for (j=0;j<k+l;j++)
{
for (i=0;i<10000;i++);
}
}
void ENABLE (void)
{
EL=1;
102
Application 4-' Chimney Sentinel
delay(l);
EL=0;
delay(l);
}
void INIT(void)
{
// Initialization of the LCD by giving the proper
commands.
}
RS=0;
RW=0;
EL=0;
PI = 0x38; // 2 lines and 5*7 matrix LCD.
ENABLE()
ENABLE()
ENABLE()
ENABLE()
PI = 0x06; //Shift cursor to left
ENABLE();
PI = OxOE; // Display ON, Cursor Blinking
ENABLE();
PI = 0x01; // Clear display Screen
ENABLEQ;
void main (void)
{
int unit, tens, hundred, unitl, tensl, hundredl;
unsigned char d;
a=0;
b=0;
c=0;
while(l)
{
Pl=0xff;
SOC=l;
delay (8);
SOC=0;
delay (8);
Embedding Microcontroller in Routine Applications 103
SOC=l;
delay (8);
d=Pl;
if(d>40)
{
BUZZ=1; // switch on the buzzer if temp is greater than 40
}
else
{
BUZZ=0;
}
unit = (d%10);
tens = (d/10)%10;
hundred = (d/100);
unit = (unit + 0x30);
unit 1 =unit+unit ;
tens = (tens + 0x30);
tensl=tens+tens;
hundred = (hundred + 0x30);
hundred 1 = hundred +hundred ;
INIT();
LINE(l);
P0=hundredl;
ENABLE();
P0=tensl;
ENABLE();
P0='.';
ENABLE();
PO=unitl;
ENABLE();
PO='c';
ENABLEi
}
}
104
Application 5: Who ? s First Timer
LCD
CeO 067 ft* *v &i
I :».
"~>
V — V — ¥
K
♦5v
10K
' ■■■i
E~
Pt» ''or Pm Pj Rj .
Vac
XTAL1
* P.* »".. P.. P- P.. *
AT89 S 52
P t ,
5^?
^^ fi?
3% r* j3 a
J L_JL_! t — at
C* D.' A ft C S«
C1K
■j^?« ADC 0808
j^ * C 4 t I. * K t «.
*\ *\ '! a l l \ *l 6 I
IK
■Wmv
"C»wy
BlizemS
JKtiH^Sqwwk*)
Figure 6.4 Circuit diagram of microcontroller based chimney sentinel unit
6.5 Application 5: Who's First Timer
This unit is ideal as a timer for quiz competitions. The person who
first presses the key will be detected and his or her name will be displayed
on LCD. The unit also sounds a buzzer to indicate that key has been
pressed. The application is designed for eight users but can be modified
easily to accommodate mode number of users.
Program Source Code
#include <REG52.H>
^include <stdio.h>
* special function register declarations
* for the intended 8051 derivative */
sbit RS =
sbit RW
sbit EL :
P2 A 0;
: P2 A 1;
P2 A 2;
Embedding Microcontroller in Routine Applications
105
sbit Rl = P0 A 0;
sbit R2 = P0 A 1;
sbit R3 = P0 A 2;
sbit R4 = P0 A 3;
sbit CI = P0 A 4;
sbit C2 = P0 A 5;
sbit C3 = P0 A 6;
sbit C4 = P0 A 7;
sbit buzzl= P3 A 0;
sbit buzz2= P3 A 1
sbit buzz3= P3 A 2
sbit buzz4= P3 A 3
sbit buzz5= P3 A 4;
sbit buzz6= P3 A 5
sbit buzz7= P3 A 6
sbit buzz8= P3 A 7
void delay (int);
void INIT(void);
void ENABLE (void);
void LINE(int);
int keyb(void);
void LINE(int i){
if (i==l) {
RS=0;
RW=0;
P 1=0x80;
ENABLE();
RS=1;
}
else
{
RS=0;
RW=0;
Pl=0xC0;
ENABLE();
RS=1;
}
106
Application 5: Who ? s First Timer
}
void delay (int k)
{
int i,j;
for (j=0;j<k+l;j++){
for (i=0;i<100;i++);
}}
void ENABLE (void)
{
EL=1;
delay(l);
EL=0;
delay(l);
}
void INIT(void)
{
}
RS=0;
RW=0;
EL=0;
PI = 0x38;
ENABLEO
ENABLEQ
ENABLE()
ENABLE()
PI = 0x06;
ENABLEO;
PI = OxOE;
ENABLE();
PI = 0x01;
ENABLEO;
// Initialization of the LCD by giving the proper
commands.
2 lines and 5*7 matrix LCD.
//Shift cursor to left
// Display ON, Cursor Blinking
Clear display Screen
int keyb(void){
int key=0;
Cl=l
C2=l
C3=l
C4=l
//8user
Embedding Microcontroller in Routine Applications 107
R1=0:
R2=l
R3=l
R4=l
if (C1==0)
{
key = 1;
buzzl=0;
}
if (C2==0)
{
key = 2;
buzz2=0;
}
if (C3==0)
{
key = 3;
buzz3=0;
}
if (C4==0)
{
key = 4;
buzz4=0;
}
Rl=l
R2=0:
R3=l
R4=l
if (C1==0)
{
key = 5;
buzz5=0;
}
if (C2==0)
{
key = 6;
buzz6=0;
}
if (C3==0)
108
Application 5: Who ? s First Timer
{
key = 7;
buzz7=0;
}
if (C4==0)
{key = 8;
buzz8=0;
}
return(key);
}
void main(void)
char arrayl[] =
char array2[] =
char array3[] =
char array4[] =
char array5[] =
char array6[] =
char array7[] =
char array8[] =
{
jivan" ;
kunal" :
rupesh'
chari" ;
roy" ;
jesni";
vinod"
John" ;
char *p,key;
int j,i;
INIT();
LINE(l);
j=0;
while(l){
j=0;
j = keyb();
if(key==l){
for (i=0;i<8;i++){
p=&; array 1;
Pl= *p++;
ENABLE();
}}
if(key==2){
for (i=0;i<8;i++){
p=&array2;
Pl= *p++;
ENABLEQ;
Embedding Microcontroller in Routine Applications 109
}}
if(key==3){
for (i=0;i<8;i++){
p=&array3;
Pl= *p++;
ENABLE();
}}
if(key==4){
for (i=0;i<8;i++){
p=&array4;
Pl= *p++;
ENABLE();
}}
if(key==5){
for (i=0;i<8;i++){
p=&array5;
Pl= *p+ + ;
ENABLE();
}}
if(key==6){
for (i=0;i<8;i++){
p=&array6;
Pl= *p+ + ;
ENABLE();
}}
if(key==7){
for (i=0;i<8;i++){
p=&array7;
Pl= *p++;
ENABLE();
}}
if(key==8){
for (i=0;i<8;i++){
p=&array8;
Pl= *p++;
ENABLE();
}}
delay (400);
}
}
"^£ "^£ "^l^ "^£ *& *& "^£ "£? "^£ "^£ "£? "£? "£? "£? "^£ "^£ *& "^£ *& "^£ "^£ *& *& "^l^ "^l^ *& "^£ *& "^£ *& "^C "^£ *& "^£ "^£ *& "^£ "^£ *& "^£ "^£ *& "^£ *& "^£ "^l^ "^l^ "^l^ ^l^ "^l^ "^£ "^£ *& "^£ *& "^£ "^£
110
Application 6: Counting Cars
Buzzed
+Vcc
1K
Key 1
User!
Buzzer-2
KEY-2
User 2
P
+Vcc
10K
I
+VCC VSS VEE
LCD (16X2)
RS WW EN
j > A , .
7Y
Q_ D. Q. □_
AT 89 S 52
Q. £L
Q. Q_ qT oT qT dT qTu. Q.Q-
User3
User4
User5
User7
Bu??Br-7
hu.' -■-■ ir t-i
KLY U
User6
Figure 6.5 Circuit diagram of Who's first timer
6.6 Application 6: Counting Cars
As shown in Figure 6.6, IR transceiver is connected to the port pin
PO.O (sensor) through which the number of cars are counted as they pass
through the passage and interrupt the IR link. The count is displayed
on the LCD connected to port PI. The system is able to count the cars
maximum up to 9999.
Program Source Code
^include <REG52.H> /* special function register declarations
^include <stdio.h> /* for the intended 8051 derivative */
sbit sensor = P0 A 0; // IR sensor input
sbit RS = P2 A 0;
sbit RW = P2 A 1;
sbit EL = P2 A 2;
unsigned int unit, ten, hundred, tenth, count;
Embedding Microcontroller in Routine Applications
111
void delay (int);
void INIT(void);
void ENABLE(void);
void LINE(int);
int updatecount(void); /* Function for update the count after passing
the car through the passage*/
int updatecount()
{if (sensor==l)
{
count =count+l;
}
else
{
count = count +0;
}
return (count);
When the input pin detects the pulse incre-
ment the count by one otherwise keep it as it
was
*
// increment count by 1
// keep count unchanged
returns the updated count value for next reference
}
void LINE (int i) /* function to define the display characters on LCD
on specified line */
{
}
if (i==i
{
RS=0;
RW=0;
PI =0x80;
ENABLE();
RS=1;
}
else
{
RS=0;
RW=0;
Pl=0xC0;
ENABLE();
RS=1;
}
Force cursor to beginning of the first line
Enable LCD
Reset the LCD
Force cursor to beginning of the second line
112
Application 6: Counting Cars
void delay (int k) // Delay function
{
int i,j;
for (j=0;j<k+l;j++) // Delay loop
{
for (i=0;i<10000;i++);
}
}
Function to Enable the LCD
// Give high to low pulse to enable pin of
the LCD
LCD of 2 lines and 5x7 matrix
void ENABLE(void)
{
EL=1;
delay(l);
EL=0;
delay(l);
}
void INIT(void) // Function to Initialize the LCD
{
RS=0;
RW=0;
EL=0;
PI = 0x38;
ENABLEO
ENABLE()
ENABLE()
ENABLE()
PI = 0x06;
ENABLEO;
PI = OxOE;
ENABLE();
PI = 0x01;
ENABLEO;
}
void main (void)
{
int count =0;
Shift cursor to right
Display on, cursor blinking
Embedding Microcontroller in Routine Applications
113
int k;
char *p;
char array[] = "No of Cars="; /* Array to display the characters "No
of Cars=" on the LCD */
INITi
while (1
{
count= updatecount(); /* Assign the returned new value to update the
count */
/* Points the next location on the LCD to
display the character*/
p=&array;
// Increment the pointer
for (k=0;k<17;k++)
{
if (k==0)
LINE(l);
Pl= *p+ + ;
ENABLE();
LINE(2);
unit =(count%10);
ten=(count/10)%10; /* Display no of cars and the count on LCD
on respective decimal position. The character
to display should be in ASCII form.*/
hundred= (count/ 100)% 10;
tenth= (count/ 1000);
Pl= (tenth+0x30);
ENABLE();
Pl= (hundred+0x30);
ENABLE();
Pl= (ten+0x30);
ENABLE();
Pl= (unit+0x30);
Send the ASCII data to LCD
ENABLEQ;
}}
114
Application 7: Anonymous Voting
33PF
^1—
DXTAL
^r
^ 33PF
+5V
Vcc
XTAL
XTAL2
P2.7
P2.1
P2.0
P2.0
P1.0
AT89S52
Po.o
GND
X
\
EN Vcc
R/W
RS
VEE
Vss
D7 LCD
HD44780
Do (16x2)
+5V
r
10K
+Vcc
Photo transistor
Road
Figure 6. 6 Circuit diagram of the system for counting cars
6.7 Application 7: Anonymous Voting
A useful device for taking the audience poll regarding a lecture or any
other issue is described in this application. This device will be passed
on to each and every member of the audience one by one. A message
appears on the LCD as regards to whether the lecture is satisfactory or
otherwise. Accordingly the user has to press key 1 or 2. The poll will be
displayed as soon as key 3 is pressed.
Program Source Code
#include <REG52.H>
^include <stdio.h>
P2 A 0;
: P2 A 1;
P2 A 2;
sbit BU = P2 A 4:
sbit RS :
sbit RW
sbit EL :
/* special function register declarations
/* for the intended 8051 derivative */
// LCD control signals
// Buzzer as a output
_ r>nAn.
sbit Rl = P0 A 0;
Hex keypad connections
Embedding Microcontroller in Routine Applications
115
sbit R2 = P0 A 1;
sbit R3 = P0 A 2;
sbit R4 = P0 A 3;
sbit CI = P0 A 4;
sbit C2 = P0 A 5;
sbit C3 = P0 A 6;
sbit C4 = P0 A 7;
void Delay (int);
void INIT(void);
void ENABLE (void);
void LINE(int);
int keyb(void);
void LINE (int i)
{
if (i==l) {
RS=0;
RW=0;
PI =0x80;
ENABLE();
RS=1;
}
else
{
RS=0;
RW=0;
Pl=0xC0;
ENABLE();
RS=1;
}
}
void delay (int k)
{
int i,j;
for (j=0;j<k+l;j++){
for (i=0;i<100;i++);
/* Function for the LCD display line selection
and giving the respective commands to LCD *
Delay function
}}
116
Application 7: Anonymous Voting
void ENABLE(void)
{
EL=1;
delay(l);
EL=0;
delay(l);
}
Function to Enable the LCD. Give high
to low pulse on EL.
{
}
void INIT(void) /* Initialization of the LCD by sending the
commands sequentially */
RS=0;
RW=0;
EL=0;
PI = 0x38;
ENABLE()
ENABLEQ
ENABLEQ
ENABLEQ
PI = 0x06;
ENABLE();
PI = OxOE;
ENABLE();
PI = 0x01;
ENABLEQ;
int keyb(void)
{
int key=0;
Cl=l
C2=l
C3=l
C4=l
Keyboard scanning function. Checks which
key is pressed.
R1=0:
R2=l
R3=l
R4=l
Embedding Microcontroller in Routine Applications
117
if (C1==0) key = 1
if (C2==0) key = 2
if (C3==0) key = 3
if (C4==0) key = 4
Rl=l
R2=0
R3=l
R4=l
if (C1==0) key = 5
if (C2==0) key = 6
if (C3==0) key = 7
if (C4==0) key = 8
Rl=l
R2=l
R3=0
R4=l;
if (C1==0) key = 9;
if (C2==0) key = 10
if (C3==0) key = 11
if (C4==0) key = 12
Rl=l
R2=l
R3=l
R4=0;
if (C1==0) key = 13
if (C2==0) key = 14
if (C3==0) key = 15
if (C4==0) key = 16
return (key);
}
void main (void)
{
char votel[] = "Lecture is satisfactory: Press 1"; /* Array for the
characters to display
on the LCD. */
char vote2[] = "Lecture is not up to mark: Press 2";
118
Application 7: Anonymous Voting
char *p; // Pointer to point the next character in the
array
int j,i;
INIT();
LINE(l);
j=0;
while(l)
{ /* When key 1 is pressed matter raised is ok */
j=0;
j = keyb();
if (J==l){
p=&votel; // Memory address define to array and defined a pointer to
point that data.
for(i=0;i<17;i++)
{
if(i==0) // Display the data on the first line on the LCD
screen
LINE(l);
if(i==8)
LINE(2); // Display the data on the second line on the LCD screen
Pl= *p++; // Pointer is incremented and the data pointed by pointer
is sent on the port 1.
ENABLE();
Delay (200);
}
if (j==2){ /* If key 2 is pressed then the vote is for the matter
is not enough */
p=&vote2;
for(i=0;i<17;i++)
{
if(i==0)
LINE(l);
if(i==8)
LINE(2); // Display the content on line 2
Pl= *p++; // Increment the pointer
ENABLE();
Delay (200);
}
}
}}} //End of the main
"^l^ "^l^ *& *& "^£ "^£ *& "^£ "^£ *& "^£ "^£ "^r£ "^£ *& "^r£ "^£ "^l^ *& "^£ *& "^£ "^£ *& "^£ *& *& *& "£? *& "^£ *& "^£ "^£ "^£ "^£ *& *& "^£ *& "^£ "^£ *& "^£ "^£ *& "^£ *& *& "^£ *& "^£ "^£ *& "^£ "^£ *&
Embedding Microcontroller in Routine Applications
119
33PF
12MHzQ] XTAL
33PF
& 10K
6.8
Figure 6. 7 Circuit diagram of unit for anonymous voting
Energy Efficient Lighting
Using Microcontroller
Sometimes the incandescent light bulb is referred to as a "heat bulb,"
because 90% of the electricity delivered to it comes out as heat. Precisely
we have used this property to build a laboratory type PID application to
illustrate the code in Chapter 6. However, the theme of the present chap-
ter is energy efficient lighting using microcontrollers. With the growing
concern about the energy crisis, almost all the industrialized countries
are now coming out with new methods to save energy, especially electri-
cal energy. It is estimated that the yearly usage of lighting for a single
office room is 1000 h which leads to 20 KWh/m 2 for a light source which
gives 20W/m 2 . With a microcontroller-based light switching or even
dimming applications a 50% savings can be achieved. Recently, Freescale
Semiconductor has come out with a new 8-bit HC908LB8 microcontroller
that offers single-chip solution for energy-efficient lighting systems. How-
ever, the applications developed in this chapter are based on AT89S52
microcontroller.
Application 8: Optimize the Electric Power
Consumption in the Corridors
In the long corridors of the hotels, unnecessary electricity is consumed
on the lights. Ideally when no one is there the lights should be switched
off. As the person passes from one end to the other the corresponding
120
Energy Efficient Lighting Using Microcontroller
H2V
33W
Array
Of
IRLED,
-12V
A
s?
a*
C
^ 33ft
O
R
5?
R
I
SP
D
5P
R
5?
i
r ?
470 i
: v
: v
\
Array CM IR Photo transistors
4701!
iVee
P
P ° A
p » T
p a
9
p S
P 5
2
p
vss
p
p
V, I23CV}
3301 (
V„ (230V)
£H?
a 1 .
MOCWttl
BuiDi
*Vcc
V, (230V)
2^
i>Hv
BulES
Figure 6. 8 Circuit diagram of the system for auto switching of lights in the corridor
lights should be switched on so that he or she will be guided toward the
corridor end. This problem is solved by using arrays of pairs of IR LEDs
and phototransistor throughout the corridor placed at equal interval as
shown in the block schematic. The array of IR LEDs are in a continuous
emitting mode. The corresponding IR phototransistors are aligned at
45° for maximizing sensitivity. Value of the resistance (1M(] to 470fi)
connected to the collector of the phototransistor decides its sensitivity.
When the IR link breaks due to the person passing the corridor, a low to
high going transition is detected by the port lines. The corresponding
bulbs connected to port 1 are made ON and OFF so as to light the
corridor as the person makes his way to the other end.
Program Source Code
#include <REG52.H> t
^include <stdio.h>
/* for the intended 8051 derivative
special function register declarations
_ DnAi
sbit sensorl= PO 0;
/* Output from the 8 sensors is connected to
the port pins of the port */
sbit sensor2= P0 A 1
sbit sensor3= P0 A 2
sbit sensor4= P0 A 3
Embedding Microcontroller in Routine Applications
121
sbit sensor5 :
sbit sensor6 :
sbit sensor 7-
sbit sensor^
P0 A 4;
P0 A 5;
P0 A 6;
P0 A 7;
/* Connecting the relays to on/off the power to the port 1
sbit RL1= P1 A 0:
sbit RL2= P1 A 1
sbit RL3= P1 A 2
sbit RL4= P1 A 3
sbit RL5= P1 A 4
sbit RL6= P1 A 5
sbit RL7= P1 A 6
sbit RL8= P1 A 7
void main (void)
{
P0=0x00;
Pl=0x00;
while(l)
{
if (sensor 1==1)
RL1=1;
// Main function
Sense the first sensor
If its output is high then switch the relay on
else if (sensor2==l) // otherwise check the second sensor.
{
RL1=0; // Off relay 1 and on relay 2
RL2=1;
}
else if (sensor3==l)
{
RL3=1;
RL2=0;
}
else if (sensor4==l)
{
RL4=1;
RL3=0;
}
else if (sensor5==l)
122 Energy Efficient Lighting Using Microcontroller
{
RL5=1;
RL4=0;
}
else if (sensor6==l)
{
RL6=1;
RL5=0;
}
else if (sensor7==l)
{
RL7=1;
RL6=0;
}
else if (sensor8==l)
{
RL8=1;
RL7=0;
}
}
}
Chapter 7
Microcontroller-based Measurement
and Control Applications
7.1 Application 1: Reading a PWM Waveform
Using Microcontroller
There are many applications in which the microcontroller is used as a
PWM generator for controlling purpose. For instance, the servo motor
control or even the temperature controller can be driven on the basis of
ON time modulation. However, in the following application, the PWM
waveform generated by IC 555 timer is monitored by the microcontroller
AT89S52 through port pin 2.4. The ON-time and OFF-time of the PWM
are displayed on the LCD. The application may be used to interface
resistive sensors like thermistor to display the temperature directly. The
main advantage of the PWM-based measurement is the possibility of
theoretically infinite resolution of the measurement.
Program Source Code
^include <REG52.H> /* special function register declarations */
/* for the intended 8051 derivative */
sbit RS = P2D;
sbit RW = P2 A 1;
sbit EN = P2 A 2:
sbit IN = P2 A 4; /*input from 555 oscillator*/
void delay (int);
void INIT(void);
void ENABLE(void);
voidLINE(int);
123
J.S. Parab et al. (eds.), Exploring C for Microcontrollers, 123-138.
© 2007 Springer.
124 Application 1: Reading a PWM Waveform Using Microcontroller
int ONTIME(int);
int offtime(int);
void LINE (int i){
if (i==l) {
RS=0;
RW=0;
Pl=0x80;
ENABLE();
RS=1;
}
else
{
RS=0;
RW=0;
Pl=0xC0;
ENABLE();
RS=1;
}
}
void delay ()
{
int i,j;
for (j=0;j<10;j++){
for (i=0;i<100;i++);
}}
void ENABLE (void)
{
EN=1;
delay ();
EN=0;
delay ();
}
void INIT(void) // Initialization of the LCD by giving the proper
commands
{
RS=0;
RW=0;
EN=0;
Microcontroller-based Measurement and Control Applications
125
}
PI = 0x38;
ENABLE()
ENABLEQ
ENABLEQ
ENABLEQ
PI = 0x06;
ENABLE();
PI = OxOE;
ENABLE();
PI = 0x01;
ENABLEQ;
2 lines and 5*7 matrix LCD
//Shift cursor to left
Display ON, Cursor Blinking
Clear display screen
int ONTIME(int m){
if (m==l)
{
IN=1;
TMOD=0x01;
TR0=0;
TF0=0;
TL0=0x00;
TH0=0x00;
while(IN);
while(!IN);
to measure On time
input to 8052 from 555 osc :
check for rising edge
TR0=1;
while(IN);
TR0=0;
}
if(m= =2)
{
IN=1;
TMOD=0x01;
TR0=0;
TF0=0;
TL0=0x00;
TH0=0x00;
check for falling edge
to measure offtime'
while(!IN);
while(IN);
check for falling edge
TR0=1;
126 Application 1: Reading a PWM Waveform Using Microcontroller
while(!IN); // check for rising edge
TR0=0;
}
return((TH0*256)+TL0);
}
void main (void){
int unit, tens, hundred, thousand, tenthou, x;
char code dis3[] = "Fre in HZ=";
char *p;
int i,j,k,freq,l;
while(l) {
for (x=l;x<=3;x++){
if(x==l)
{
i = ONTIME(x);
k=i;
}
if( x = =2)
{
i = offtime(x);
l=i;
}
if ( x = =3)
{
freq=k+l;
i=l/freq ; //convert time to frequency
}
unit = (i%10);
tens = (i/10)%10;
hundred = (i/100)%10;
thousand = (i/1000)%10;
tenthou = (i/10000)%10;
unit = unit + 0x30;
tens = tens + 0x30;
hundred = hundred + 0x30;
thousand = thousand + 0x30;
tenthou = tenthou + 0x30;
Microcontroller-based Measurement and Control Applications 127
INIT();
LINE(l);
p=&dis3; // display freq on LCD
for (j=0;j<8;j++){
Pl=* p+ + ;
ENABLE();
}
LINE(2);
Pl=tenthou;
ENABLE();
Pl=thousand;
ENABLE();
Pl=hundred;
ENABLE();
Pl=tens;
ENABLE();
Pl=unit;
ENABLE();
}
7.2 Single Set-point On/Off Controller
An on/off controller is the simplest form of temperature control
device. In the following application, the process consists of a simple
heating unit based on Neon bulb. The sensor used is LM35, the output
of which is conditioned by using OP07. The digitization is done by using
ADC7135. The end of conversion is sensed by using the port pin 3.4 of
AT89S52. The data is taken in using port PO. The set-point is kept at
40, but the same can be varied based on the application needs. The LCD
displays the set-point as well as current temperature. The controlling
is done by using a relay driven by port line P2.3 through transistor
2N2222.
128
Single Set-point On/Off Controller
o
o
o
o
o
o
+3
o
o
Oh
*"1
Microcontroller-based Measurement and Control Applications
129
LCD
Module
Do D 7
M89552
Microcontroller
Relay
r
Do
D 7
ADC 7135
LM
35
Figure 7.2 Block schematic of microcontroller based on/off controller
Program Source Code
#include<REG52.H>
void busy _count (void);
void LINE(int a);
void ENABLE(void);
void init(void);
//void init Jed (void);
sbit elk = P3 A 5;
sbit BUSY=P3 A 4;
sbit RS = P2 A 0;
sbit RW = P2 A 1;
sbit EL = P2 A 2;
sbit RL = P2 A 3;
int count _u, count _t;
void main()
{
TMOD=0x50;
BUSY=1;
init();
busy_count();
}
start timer in function*/
130
Single Set-point On/Off Controller
start counter 1
void busy _count (void)
{
int count, count 1;
TR0=0;
TH0=0x00;
TL0=0x00;
count=0x00;
while(BUSY);
while(!BUSY);
while(BUSY)
{
TR0=1;
}
while(!BUSY)
{
TR0=0;
}
count=((TH0*256)+TL0);
countl=count— 10000;
count_u=count%10;
count_t=(count/10)%10;
RS=1;
LINE(l);
if (count >40)
when busy goes low stop counter'
//if temperature is greater than 40 than turn off
the relay
{
RL=1;
}
else
{
RL=0;
}
Pl=(count_t+0x30);
ENABLE();
Pl=(count_u+0x30);
ENABLEi
}
void init(void){
RS=0;
RW=0;
EL=0;
Microcontroller-based Measurement and Control Applications 131
PI = 0x38;
ENABLE()
ENABLE()
ENABLE()
ENABLE()
PI = 0x06;
ENABLE();
PI = OxOE;
ENABLE();
PI = 0x01;
ENABLE();
}
void LINE(int i){
if (i==l) {
RS=0;
RW=0;
Pl=0x80;
ENABLE ();
RS=1;
}
else
{
RS=0;
RW=0;
Pl=OxCO;
ENABLE();
RS=1;
}
}
void ENABLE(void)
{
EL=0;
//delay(l);
EL=1;
//delay(l);
EL=0;
132
Single Set-point On/Off Controller
HK
+
X
(fi
W
o Q
>
«o
1" A
g «
M
wa
>
sa
-:r*
g
o
H
H*
>
O
uj ro
m
4
nr
o
o
o
to
o
o
CD
i
fH
'o
o
o
o
o
4h
o
Co
bJO
ct
2
O
O
Microcontroller-based Measurement and Control Applications
133
+Vcc
o
10K
1
1
Vcc
Vss
VEE
HD 44780 (16X2)
LCD
CO
Q Q UL C£ LU
^^\ A * 7K
33PF
12MH [ ] XTAL
+Vcc
L
33PF
d
a
1
a
Vcc p D D p p
■2.0 ~2 7 "0.4 '0.5 "0 6
XTAL1
XTAL2
GND
AT 89S52
D o
Battery 3.6V
33PF =J= =^
1
SCL
?— i
33PF
1N41
1N41
H<F
100a
1 , 1N41
6 5
PCF 8583
12 3 4
T
10 M F
it*
1
+ Vcc
10K
SDA
8 7 6 5
AT 2404
12 3 4
10K
Figure 7.4 Circuit diagram for I C interface
7.3
Application 3: I 2 C Interface with Serial
EPROM
In the context of microcontroller-based process control applications,
many embedded designers are experiencing the inadequacy of the on-chip
memory. The simplest alternative is to interface an external EPROM.
I 2 C-based serial peripherals offers maximum circuit efficiency with the
interface simplicity. The prime advantage of this interface is that only
two lines (clock and data) are required for full duplexed communica-
tion between multiple devices. The operating range of the interface is
typically 100 KHz to 400 KHz. I 2 C protocol assigns a unique address to
every peripheral. The peripheral can act as a receiver and/or transmitter
depending on its functionality.
134 Application 3: I 2 C Interface with Serial EPROM
The application developed here illustrates the I 2 C-enabled code devel-
opment for the PCF8583 Real-Time Clock and AT2404 Serial EPROM.
In many data logging applications the data needs to be collected with
the time stamp. The RTC PCF8583 will facilitate the time stamping
operation while the acquired data can be stored in the serial EPROM
AT2404.
Program Source Code
"^£ "^r£ *& *& "^£ *& *& *& "^l^ "^l^ "^l^ "^l^ "^l^ "^l^ *& *& "^l^ *& *& ^l^ *& *& *& *& *& *& *& *& *& "^£ *& *& "^l^ *& *& ^l^ *& "^£ ^l^ *& *& *& *& "^l^ "^l^ *& "^l^ *& *& *& "^r£ *& *& *&
^include <reg52.H>
sbit sda=P0 A 0;
sbit scl=P0 A l;
sbit led=Pl A 0;
sbit RS=P0 A 4;
sbit RW=P0 A 5;
sbit EN=P0 A 6;
int x;
unsigned char dat;
int ack(void);
void start (void);
void stop (void);
void delay (void);
void enable(void);
void add (int);
void ini(void);
void reset (void);
unsigned char read(void);
void lcd(unsigned char);
void start (void)
{
sda=l;
delay ();
scl=l;
delay ();
sda=0;
delay ();
}
Microcontroller-based Measurement and Control Applications 135
void stop (void)
{
sda=0;
delay ();
scl=l;
delay ();
sda=l;
delay ();
}
void delay (void)
{
int i;
for(i=0;i<30000;i++);
for(i=0;i<200;i++);
}
void add(d)
{
int i;
for(i=0;i<8;i++)
{
scl=0;
delay ();
sda=d>>7;
scl=l;
delay ();
d=d«l;
}
scl=0;
delay ();
}
int ack(void)
{
scl=0;
delay ();
sda=l;
delay ();
136 Application 3: I 2 C Interface with Serial EPROM
scl=l;
delay ();
return sda;
}
void reset (void)
{
int i;
for(i=0;i<9;i++)
{
scl=0;
delay ();
scl=l;
delay ();
if(sda==l)
break;
}
}
unsigned char read (void)
{
unsigned char var=0;
int i;
for(i=0;i<8;i++)
{
scl=0;
delay ();
scl=l;
var=var|sda;
delay ();
var=var<<l;
}
scl=0;
delay ();
return var;
}
void ini(void)
{
RW=0;
RS=0;
Microcontroller-based Measurement and Control Applications 137
P2=0x38;
enable();
enable ()
enable()
enable ()
P2=0x06;
enable ();
P2=0x0E;
enable ();
P2=0x01;
enable();
RS=1;
}
void lcd(unsigned char dat)
{
int hun, ten, unit;
hun=dat/100;
ten=((dat/10)%10);
unit = dat % 10;
hun=( hun +0x30);
P2=hun;
enable ();
delay ();
ten=ten+0x30;
P2=ten;
enable();
delay ();
unit=unit+0x30;
P2=unit;
enable ();
delay ();
}
void enable (void)
{
EN=1;
delay ();
EN=0;
delay ();
}
2
138 Application 3: VC Interface with Serial EPROM
void main(void)
{
ini();
while(l)
{
Pl=0x00;
reset ();
start ();
add(OxAO);
led=l;
x=ack();
led = x;
delay ();
delay ();
led=l;
if ( x = =0)
{
add(0x05);
x=ack();
led = x;
delay ();
delay ();
}
led=l;
start ();
add(OxAl);
dat=read();
lcd(dat);
scl=l;
sda=l;
stop();
}
}
"^z *& "^z *& "^c "^z *& "^c "£? *& *& *& *& "^c *& "£? "^z *& *& "£? *& "^z *& *& "^c *& *& "^z *& "^c "^z *£c "^c "^z "^c "£? *& *& "^z *& "^c "^z *& *& "^z *& "^z "^z *& "^z *& "^c "^z *&
Chapter 8
Securing Your Embedded System Application
8.1 Security Challenges in Embedded Systems
The applications of embedded systems are growing in the areas such
as cell phones, cars, spacecraft, biomedical sensitive, and defense. The
main concern for deployment in these application sectors is security.
Security has been the subject of intensive research in the context of
general-purpose computing and communications systems. In computing
and networking products there are established devices and algorithmic
methodologies for ensuring the security of the code. The security con-
cerns about the embedded systems are well covered in many references
[38; 39; 40; 41; 42; 43]. Security is often misconstrued by embedded sys-
tem designers as the addition of features such as specific cryptographic
algorithms and security protocols to the system. In reality, it is a new
dimension that designers should consider throughout the design process,
along with other metrics such as cost, performance, and power. The chal-
lenges unique to embedded systems require new approaches to security
covering all aspects of embedded system design from architecture to
implementation. Security processing, which refers to the computations
that must be performed in a system for the purpose of security, can
easily overwhelm the computational capabilities of processors in both
low- and high-end embedded systems [38]. This challenge, which we
refer to as the "security processing gap," is compounded by increases
in the amounts of data manipulated and the data rates that need to
be achieved [38]. Equally daunting is the "battery gap" in battery-
powered embedded systems, which is caused by the disparity between
rapidly increasing energy requirements for secure operation and slow
improvements in battery technology. The final challenge is the "assur-
ance gap," which relates to the gap between functional security measures
(e.g., security services, protocols, and their constituent cryptographic
algorithms) and actual secure implementations.
139
J.S. Parab et al. (eds.), Exploring C for Microcontrollers, 139-150.
© 2007 Springer.
140 Application 1: Authentication for Your Embedded System Application
The case studies developed in this chapter specifically focus on the
security aspects of the embedded systems. The first case study offers
the security by checking the user's login ID and password just like a
typical interface presented by multi-user OS. The second case study
allows the user to let in provided he or she enters the password in a
given time. While the third application illustrates the methodology of
writing the routines in the same manner as that of computer BIOS,
which has inherent code security.
8.2 Application 1: Authentication
for Your Embedded System Application
The setup shown in Figure 8.1 is used for this application. The pro-
gram prompts the user to enter his user ID by displaying a message
"LOGIN" on the LCD. The user is expected to enter his ID using the
PC keyboard. Then the program displays a message "password" on the
LCD to prompt the user to enter the password. After entering the pass-
word, the program will check whether the entered information is correct
or not.
The system can also be used for cabinet lock-up or for any keyboard-
based security implementation.
Program Source Code
^include <REG52.H> /* special function register declarations */
/ * for the intended 8051 derivative */
^include <stdio.h> /* prototype declarations for I/O functions */
sbit RS = P2 A 0;
sbit RW = P2 A 1;
sbit EL = P2 A 2;
void INITt ();
void delay (int);
void INIT(void);
void ENABLE(void);
void LINE(int);
char array[]= "LOGIN:";
char pass[]="EMBEDED";
char Access[] = "CORRECT";
char denied[] = "WRONG";
Securing Your Embedded System Application 141
void INITtQ // function to Initialize the timer
{
TMOD=0x20;
THl=0xFD;
SCON=0x50;
TR1=1;
}
void LINE (int i) // Enable the line function
{
if (i==i)
{
RS=0;
RW=0;
Pl=0x80;
ENABLE();
RS=1;
}
else
}
{
RS=0;
RW=0;
Pl=0xC0;
ENABLE();
RS=1;
}
void delay (int k) // invoking delay function
{
int i,j;
for (j=0;j<k+l;j++)
{
for (i=0;i<10000;i++);
}
}
void ENABLE (void) // invoking the enable function
{
EL=1;
142 Application 1: Authentication for Your Embedded System Application
delay(l);
EL=0;
delay(l);
}
void INIT(void)
{
RS=0;
RW=0;
EL=0;
PI = 0x38;
ENABLE();
ENABLEQ;
ENABLEQ;
ENABLEQ;
PI = 0x06;
ENABLE();
PI = OxOE;
ENABLE();
PI = 0x01;
ENABLE();
}
initialization of LCD display 5
void main (void) // main function
{
char b,var;
char *p;
int i,j,k;
while (1)
{
INIT();
LINE (1);
for (b=0;b<8;b++)
{
p=&array;
Pl= *p++; /* increment the pointer and point the
data from the array
ENABLE
}
Securing Your Embedded System Application 143
{
INITt();
RI=0;
var=SBUF;
while(IBI);
RI=0;
while(l)
{
for (i=0;i<8;i++)
{
if((pass[i])==(var[i]))
for(j=0;j<8;j++)
{
LINE(l);
p=&Access;
Pl= *p+ + ;
ENABLE();
}
else
{
LINE(l);
p=&denied;
Pl= *p++;
ENABLE();
}
RS=0;
Pl=0x01;
ENABLE();
RS=1;
}
}
}}}
144
Application 2: Timeout Waiting for Input Data
Authentication for your Embeded System Application
DB 9 Connector
10 nF
LCD
H D 44780 (16X2)
DBO-DB7 Rs Rw En
+5v
33PF
n —
r% □ XTAL
i T T
11.0592 MHz
r
T
Vcc PORT1 P 20 P.i
XTAL1
XTAL2
GND
Q_
s
x
01
3
x
AT 89 S 52
16
15 14
13
12
11
10
> o o
X
O
CtL
CM
O
CN
MAX 232
o > o
O
3
c
CN
rr
10 M F
t
10 M F
"T
+ VCC
-f6 7
Figure 8. 1 Setup for security authentication of embedded system
8.3
Application 2: Timeout Waiting for Input
Data
In this application, the security is implemented by allowing the user
to enter 10 predetermined characters (password or secret word) in a
predetermined time period. Thus this application ensures a tight secu-
rity implementation as compared to the previous as the time clause is
important.
Securing Your Embedded System Application
145
+5V
33PF
^
12MHz [ ] XTAL
33PF
Vcc
XTAL1
XTAL2
oo
GND
T
p*.
p,.
p„
p»„
10K
WSwV
I w*V»V\
• IMWV
+ 5V
10K
FN
R/W
RS
D,
Do
HD 4478Q
16X2
LCD
1K
* KEY PAD
4 X 4
MATRIX
+5V
Buzzer
BC547
Figure 8.2 Schematic for the setup for timeout waiting
It can also be used for normal data logging applications. While in-
putting the data, if the data does not arrive after some allowed time,
the wait is abandoned and some other action is taken. The request can
be retransmitted or some error message is sent to the user.
The program implemented here waits for the user to type 10 charac-
ters. The timeout for the first character is 10 seconds, and then 2 seconds
for each character thereafter. If the user does not respond within this
time, a timeout message is displayed on LCD.
Program Source Code
*& *& "^£ *& "^£ *& "^l^ *& *& "^l^ "^l^ "^l^ "^l^ "^l^ "^l^ "^l^ "^l^ *& *& "^r£ "J^ *& "^l^ "^l^ *& "^l^ *& *& "^l^ "^£ "^£ *& "^£ *& *& *& "^£ "^£ "^£ *& *& "^r£ *& "^£ "^r£ *& *& "^l^ "^l^ *& "^l^ "^l^ *& "^l^ "^l^ "^l^ "^l^ "^l^ *& "^l^ "^l^ "^l^
#include <REG52.H>
^include <stdio.h>
/* for the intended 8051 derivative
special function register declarations
146
Application 2: Timeout Waiting for Input Data
sbit RS =
sbit RW
sbit EL :
sbit BU
P2 A 0;
: P2 A 1;
P2 A 2;
P2 A 4;
LCD control signals
Buzzer
sbit Rl
sbit R2
sbit R3
sbit R4
P0 A
P0 A 1
P0 A 2
P0 A 3
Keypad connection 4x4 matrix keyboard
sbit CI
sbit C2
sbit C3
sbit C4
P0 A 4
P0 A 5
P0 A 6
P0 A 7
void delay (int); /* Stop Exection with Serial Intr. */
void INIT(void);
void ENABLE (void);
void LINE(int);
int keyb(void);
char getascii(int); // ASCII convertion to send data on LCD
char getascii(int k)
{
int ascii;
if(k<10)
ascii=k+0x30;
if (k==10)
ascii=0x30;
return (ascii);
}
// Invoking the ASCII conversion function
converts the data in to ASCII format
Returns the ASCII value to the main
routine
void LINE (int i)
I
if (i==l
{
RS=0;
function for selecting the line to display
the data on LCD
Securing Your Embedded System Application
147
}
RW=0;
PI =0x80;
ENABLE();
RS=1;
}
else
{
RS=0;
RW=0;
Pl=OxCO;
ENABLE();
RS=1;
}
void delay (int k)
{
int i,j;
for (j=0;j<k+l;j++)
{
for (i=0;i<100;i++);
}}
void ENABLE (void)
{
EL=1;
delay(l);
EL=0;
delay(l);
}
void INIT(void)
// Delay function
{
RS=0;
RW=0;
EL=0;
PI = 0x38;
ENABLE()
ENABLEQ
ENABLEQ
ENABLE ()
Invoking the function to enable the LCD
Sequential commands for the LCD
initialization
148
Application 2: Timeout Waiting for Input Data
}
PI = 0x06;
ENABLE();
PI = OxOE;
ENABLE();
PI = 0x01;
ENABLEQ;
int keyb(void)
{
int key=0;
Invoking the Keyboard scanning function
Cl=l
C2=l
C3=l
C4=l
R1=0:
R2=l
R3=l
R4=l
if (CI:
if (C2=
if (C3=
if (C4=
=0) key
0) key
0) key
=0) key
1
2:
3:
4:
Rl=l
R2=0:
R3=l
R4=l
if (CI:
if (C2:
if (C3:
if (C4:
=0) key
=0) key
0) key
=0) key
5:
6:
7:
8:
Rl=l
R2=l
R3=0:
R4=l
Securing Your Embedded System Application
149
if (C1==0) key = 9;
if (C2==0) key = 10
if (C3==0) key = 11
if (C4==0) key = 12
Rl=l
R2=l
R3=l
R4=0
if (C1==0) key = 13
if (C2==0) key = 14
if (C3==0) key = 15
if (C4==0) key = 16
return (key);
}
void main (void)
{
int j;
char arr ay []= "Enter 10 characters";
char time out [] = "Request time out" ;
INIT();
char *p;
int k;
while(l){
p=&array;
for (k=0;k<17;k++)
{
if (k==0) LINE(l);
if (k==8) LINE(2);
Pl= *p+ + ;
ENABLE();
j = keyb();
Delay(lOOOO); //10 sec delay
lf(j=0) // no key pressed
Main function
{
p=&time out;
for (k=0;k<17;k++)
{
150
Application 2: Timeout Waiting for Input Data
if (k==0) LINE(l);
if (k==8) LINE(2);
Pl= *p++;
ENABLE();
}
elseif{
for (i=0;i<9;i++)
{
Pl=getascii(j);
delay (2000);
j = keyb();
if(j=0)
{ p=&time out;
//for remaining 9 characters delay is 2 sec
2 sec
if no character is received within 2 sec
then flash "request time out on LCD screen
for (k=0;k<17;k++)
{
if (k==0) LINE(l);
if (k==8) LINE(2);
Pl= *p++;
}
ENABLEi
}
}}
References
1. http://en.wikipedia.org/wiki/Microcontroller from Wikipedia, the
free encyclopedia
2. http://www.webopedia.eom/TERM/M/microcontroller.html
3. http://www.definethat.com/define/1727.htm
4. http://www.pcmag.com/encyclopedia_term/0,2542,t=microcontrol-
ler&i=46924,00.asp
5. http://foldoc.org/7microcontroller
6. Report on World Microcontrollers Market by Frost & Sullivan
research service, published on 30 December 2005
7. http://www.intel4004.com/busicom.htm A testimonial from
Federico Faggin, its designer, on the first microprocessor's thirtieth
birthday
8. http://www3.sk.sympatico.ca/jbayko/cpul.html Section One:
Before the Great Dark Cloud
9. http://www.cpushack.net/Historyofthe8051.html The Unofficial
History of 8051 by Jan Waclawek (wek at efton.sk) edited by John
Culver
10. World Microcontrollers Market F591-26, Agency /Source: Frost &
Sullivan http://www.newswiretoday.com/news/7122/)
11. Applications for Efficiency: The Green Story, www.freescale.com
12. The 8-bit microcontroller- A hit product that supports digi-
tal still cameras (DSCs) from behind the scenes 8-bit micro-
controllers and the important role they play inside digital
cameras, Vol. 24 (14 September 2004) http://www.necel.com/
en/channel/vol_0024/vol_0024_2.html#chapterl)
151
152 References
13. http://www.bourneresearch.com/: Bourne Research is a trusted
source of market intelligence, with a specialized focus on MEMS
(MicroElectroMechanical Systems), Nanotechnology, and the con-
vergence of both.
14. SI A Raises Chip Sales Forecast, Written by Steven Waller,
Wednesday, 07 June 2006 http://e-and-f. com/index. php?option=
com_content&task=view&id=40&Itemid=2
15. http://www.cs.ucr.edu/content/esd/slide_index.html
16. http://www.industrialnewsroom.com/fullstory/26253 Cygnal
Releases World's Highest Performance 8051 Microcontroller
17. http://www.xemics.com/ or http://www.semtech.com/products/
wireless&sensing/trans/xemic.jsp XE8000 Application Specific
Microcontrollers series
18. http://www.eeproductcenter.com/micro/brief/showArticle.jhtml?
articleID= 196700958 Microcontrollers integrate power-saving
technology, Gina Roos, eeProductCenter, 12/19/2006
19. http://www.microcontroller.com Microcontrollers and DSPs - Will
They Converge? by Bill Giovino
20. http://www.edn. com/index. asp?layout=article&stt=000&articleid=
CA333669&pubdate=ll%2F13%2F2003: Microcontrollers gain
DSP attributes in "hybrid" architecture By Graham Prophet
EDN Europe, 11/13/2003
21. http://www.omimo.be/magazine/99q2/Hitachi.pdf The RISC
Challenge in DSP Processing by Dr. Manfred Schlett
22. http://www.mcjournal.com/articles/arcl01/arcl01.htm Real-Time
Debugging Highly Integrated Embedded Wireless Devices, by David
Ruimy Gonzales and Brian Branson
23. http://www.keil.com/dd/chip/3469.htm Silicon Laboratories, Inc.
C8051F120
24. www.futurlec.com/News/Dallas/InternetIC.html New Microcon-
troller is web-enabled Dallas Semiconductor Re-Engineers, Its
Microcontrollers for Network Computing
25. http://www.aldec.com/products/ipcores/ IP cores by Aldec Inc.
26. http://blogs.zdnet.com/emergingtech/wp-mobile.php?p=227&more
= 1 Emerging Technology Trends
References 153
27. http:// www. embedded. com/showArticle.jhtml?articleID=194300451
Tutorial: Improving the transient immunity of your microcontroller-
based embedded design Part 1 Defining the problem: A step
by step tutorial on EMI, ESD, and EFT problems in embedded
designs and a range of possible solutions. By Ross Carlton, Freescale
Semiconductor, Inc
28. http://www.keil.com/support/man_c51.htm On Line Manual of Keil
for C51 products
29. "Choosing a Microcontroller for Embedded System Applica-
tions", Mel Tsai http://www.egr.msu.edu/classes/ece482/Reports/
appnotes/98spr/tsaimelv/appnote.html
30. Application Note: Choosing a Microcontroller for Embedded Sys-
tems Applications Mel Tsai http://www.mtsai.net/documents/
appnote/appnote.html
31. http://www.airborn.com.au/8051/2wio8051.html 2 Wire Input/
Output for 8051 type CPU's
32. www.8052.com/users/garypeek/ : "I/O EXPANSION ROUTINES
FOR 8051 FAMILY MICROCONTROLLERS; WRITTEN BY
GARY"
33. On the verge: LEDs ready to challenge incumbent light sources in
the street lighting market: Tim Whitaker http://ledsmagazine.com/
articles/features/3/ 10/4/1: LED's magazine
34. Microcontrollers provide connectivity of HB-LED lighting prod-
ucts: Dugald Campbell http://www.ledsmagazine.com/articles/
features/2/11/1/1 LEDs Magazine
35. http://www.alldatasheet.co.kr/datasheet-pdf/pdf_kor/STMICROE-
LECTRONICS/ULN2003.html Data sheet of ULN2003
36. www.aurel32.net/elec/pcf8583.pdf Data-sheet of PCFR8583
37. http : // www . atmel . com/dyn/products/product_card . asp?part_id=
2806 Data-sheet of AT24C04
38. Security in embedded systems: Design challenges, Srivaths Ravi,
Anand Raghunathan, Paul Kocher, Sunil Hattangady, ACM Trans-
actions on Embedded Computing Systems (TECS) archive, Vol-
ume 3, Issue 3 (August 2004) table of contents, pp. 461-491, 2004,
ISSN:1539-9087
154 References
39. Ross J. Anderson, Markus G. Kuhn, Low-Cost Attacks on Tamper
Resistant Devices, Proceedings of the 5th International Workshop
on Security Protocols, p. 125-136, April 07-09, 1997
40. W. A. Arbaugh, D. J. Farber, J. M. Smith, A secure and reliable
bootstrap architecture, Proceedings of the 1997 IEEE Symposium
on Security and Privacy, p. 65, May 04-07, 1997
41. Matt Blaze, A cryptographic file system for UNIX, Proceedings of
the 1st ACM Conference on Computer and Communications Secu-
rity, pp. 9-16, 3-5 November 1993, Fairfax, Virginia, USA
42. D. Boneh, R. DeMillo, and R. Lipton, 2001. On the importance of
eliminating errors in cryptographic computations. Cryptology 14(2):
101-119
43. Jerome Burke, John McDonald, Todd Austin, Architectural sup-
port for fast symmetric-key cryptography, Proceedings of the 9th
International Conference on Architectural Support for Programming
Languages and Operating Systems, pp. 178-189, November 2000,
Cambridge, Massachusetts, USA
Index
2N2222, 127
A
A to D converter, 7, 48, 57
ADC0808, 100
ADC7135, 127
Adding your program source code, 24-25
Anonymous voting, 114-118
APIs, 14
Architectural trend, 10-14
Art of C programming for microcon-
trollers, 29-34
ASCII, 66, 113, 146
Assurance gap, 139
AT2404, 134
AT89C2051, 30, 52
AT89C51, 30, 52
B
Basic C program structure, 34
Baud rate, 17, 63, 69
Bicolour LED, 51
Blinking LED, 48
Buzzer, 58, 91, 104, 114
Conventional C, 20-21
Convergence of DSP with micro, 12
Copying startup code to your project,
22, 24
Corridor, 120
Counting cars, 110-114
D
Darlington driver, 74
Development flow for the Keil IDE,
21-26
Differences from ANSI C, 34
DIP switch, 52-53
Dominance of soft IP cores, 14
DSP, 2-3, 12
Dumping the code in microcontroller's
on-chip memory, 28
E
Energy consumption, 13, 16, 48
Energy efficient lighting, 119
Estimating interrupt latency, 63-67
Ethernet, 14, 71
C
Cafeteria Food Alert, 94-100
Chimney sentinel, 100-104
COM port, 69
Common anode, 47
Communication systems, 8
Comparison of the packages, 38
Compiler capabilities, 29
Compiling the program, 27
Configuring ports as input, 42-43
Fading RGB LED, 52
FOR construct, 44
Freescale semiconductor, 9, 119
Front desk notifier, 90-94
G
Getting familiar with the IDE, 19
Growth economics, 7
155
156
Index
H
Hardware and software issues, 17
Header files, 30
Hidden debugger, 12-13
Hitachi 44780, 54
Home automation, 78
Hyperterminal based control, 69-78
I2C bus, 46
Incandescent light bulb, 119
Increment /decrement operator, 43
Interfaces offered by Keil IDE, 21
Interrupt 4, 58
Interrupt latency, 63-67
Interrupts, 57
IR LED, 120
ISRs, 58
JTAG interface, 13
K
Keil IDE, 20-21
Keil types, 35
Keil variable extensions, 36
Keyboard, 57, 85, 140
Minutes counter, 60-63
MOC3030, 80
Multiuser OS, 140
O
OFF time, 123
ON time, 123
Opening a new project, 22
Optoisolator, 80
Packet based control, 69
Password, 140
PCF8583, 134
Phototransistor, 120
Pico power microcontrollers, 11
Podium timer, 85-90
Ports, 37
Power consumption, 11, 119
PPI8255, 46
Program the microcontroller, 28
Protocol, 5, 69, 78, 133
PWM, 123
R
RS232C, 70
RTC, 134
Running LED, 51
LCD, 54-57
LED, 46-52
LED dimmer demoboard, 51
LED moving font, 52
Lightening industry, 48
LM35, 100, 127
LOGIN, 140
Low power design, 11
M
Market trend, 8
MAX232, 70
MCU turf, 10
Microcontroller, 1
Microcontroller applications, 5-7
Microcontroller based menu card, 94-95
Scrolling LED, 49-50
Security challenges, 139
Selecting a device for the target, 22
Serial EPROM, 133-138
Seven segment LED, 60
Shift register, 46
Shifting, 45-46
Simulated mode, 27
Simulated port testing, 37
Single set point, 127
Software delay loop, 43
Special Function Register, 35, 38, 42
Square wave, 41
Standard types, 35
Stepper motor control, 74-78
Street light, 48
Index
157
w
Thermistor, 123
Timeout waiting, 144
V
Variable types, 34
Von-Neumann architecture, 10
Web enabled microcontrollers, 13-14
Who's first timer, 104
Working with Keil IDE, 20
X
X10, 78
Live Music Archive
Librivox Free Audio
Metropolitan Museum
Cleveland Museum of Art
Internet Arcade
Console Living Room
Books to Borrow
Open Library
TV News
Understanding 9/11