nds on Approach ersity D G. SHELAKE , India NISH K. KAMAT niversity , India ersity S. PARAB niversity ISH M. NAIK d by Springer, x 17, 3300 AA Dordrecht, The Netherlands. inger.com on acid-free paper ts Reserved of this work may be reproduced, stored in a retrieval system, or transmitted orm or by any means, electronic, mechanical, photocopying, microfilming, recording wise, without written permission from the Publisher, with the exception material supplied specifically for the purpose of being entered cuted on a computer system, for exclusive use by the purchaser of the work. Springer 78-1-4020-6066-3 (HB) 78-1-4020-6067-0 (e-book) ord ix e xiii wledgments xvii rocontrollers: Yesterday, Today, and Tomorrow 1 1.1 Defining 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 egrated 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 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 v ploring the Capabilities of On-Chip Resources Programming for I/O Ports, Interrupts and Timer/Counter 37 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 perterminal-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 bedding 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 6.8 Energy Efficient Lighting Using Microcontroller 119 rocontroller-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: I2C Interface with Serial EPROM 133 uring 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 erences 151 ex 155 we accept the premise that an embedded engineer is made rather born, then how does one go about making a good one? The authors s book Exploring C for Microcontrollers: A Hands-on Approach are nly “good ones”. Not only do they explore some of the influences haped themselves but they also try to shape “would-be” embedded eers. Research and developmental activities in embedded systems own in a significant proportion in the recent past. Embedded soft- design is not new to the world, but with the changing time, it ained considerable momentum in the recent past, and many young eers are strongly inclined to pursue their future in this field. The is mainly targeted to these engineers who would like to understand at depth the synergetic combination of hardware and software. e book is divided into eight chapters. Chapter 1 introduces a brief round about micro-controllers and explains how they are embed- nto products commercially available in the market to emphasize the tance of these in the daily life of mankind. It also gives an insight he architectural details and embedded system concepts for stu- projects to motivate them into this exciting field. The rest of the concentrates on software development. The integrated development onment (IDE) is introduced in Chapter 2. Again the screen shots tep-by-step procedure will certainly make the students and engi- fully understand the development process. Chapter 3 differenti- he embedded C paradigm from the conventional ANSI C. Again uthors explain how to successfully overcome the memory and time raints while developing an embedded C program. Chapter 4 gives erview of program development for on-chip resources for MCS51 y of microcontrollers. Chapters 5–8 are devoted to live case studies. e book has come out with an elegant presentation to aspiring nts and engineers from the teaching experience and technical edge the authors have put over a long time in this field. I strongly mend this book for intermediate programmers, electronics, electri- strumentation engineers or any individual who is strongly inclined ix ng by doing. Last but not the least, this book will certainly be a 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 Senthil Kumar is Head of DQE and PQCD sections of National te Sensing Agency (NRSA) an autonomous operational center Department of Space (DOS), Government of India. This is the agency in the country for receiving, processing, and distributing atellite and aerial remote sensing data and products. NRSA is also nsible for providing end-to-end solutions for utilization of data ospatial applications and information services. NRSA has a huge ve of remote sensing data acquired through Indian and foreign tes and also has the capability to acquire data pertaining to any of the globe on demand. It is one of the important centers for otion of remote sensing and geographic information system tech- ies in India. NRSA has set up satellite data processing facilities ng from data reception to utilization at various centers within and across the globe. e past few decades have witnessed evolution of microcontrollers. have revitalized a number of products or equipment in almost all including telecommunications, medical, industrial, and consumer cts. These embedded microcontroller systems now resides at the of modern life with a variety of applications in fields like con- electronics, automotive systems, domestic, and even in aerospace cts. Embedding a microcontroller in an electronics instrument or ct requires a specialized design skill which requires a synergy of ware and software skills. our day-to-day life we come across a number of embedded products. we switch on the washing machine or send an SMS on a cell phone annot prevent without thinking the mechanism and the co-working dware and software in the background. The market for such smart dded products is occupying newer and newer applications seem- impossible few years back. Last year the IDC, a premier global et intelligence firm, revealed that the embedded industry product opment was expected to be as high as $75 billion. This entails the try requirement of trained human resource with mixed skill set in hardware and software. Unfortunately the synergetic demand rdware and software or sometimes even referred to as firmware etency has led to a supply–demand gap of HR in this field. This xpressed in numerical figures led to requirement of around 150,000 dded engineers to serve the global embedded industry. This book al for all those who would like to pursue their career in the exciting of microcontroller-based embedded systems. The approach is ped- cal; first the hardware module is presented and then the associated are code in Keil C. e hardware designed is useful for engineering graduates and prac- professionals with the required knowledge and practical hands on to design with embedded systems. However, the prerequisite for ook is background of theoretical aspects of architecture of micro- ollers especially the MCS-51 family. The book starts with initial xi r is comfortable with these primitive programs which covers almost e on-chip resources, he or she can switch to more advanced ones. Scope of the Book now review the topics covered in sequence, chapter by chapter. apter 1 provides an overview of microcontrollers and their appli- ns in different domains. The architectural trends and the growth mics emphasizes the importance of the subject. The photograph of tup and the hints toward project execution will definitely boost the dence of the novice to kick-start the project with minimal resources. apter 2 is devoted to the IDE for the MCS-51 family. The simulation ingle stepping as described in this chapter will solve all the project acies of the readers. Chapter 3 illustrates the basic difference in ional C programming and embedded C. Chapter 4 deals with the amming of on-chip resources of MCS-51 family microcontrollers The theoretical details of these on-chip resources such as ports, s, etc., are completely eliminated. As the book aims at hands-on ach, the programs for the on-chip resources have been developed heir execution is illustrated in the Keil simulation environment. e last four chapters, i.e., 5–8 deal with various project case stud- everal case studies in various application domains such as lighting, urement and control, security, and domestic applications are devel- from scratch. The hardware and software developed in the form of tudies also caters to a set of mini projects, which are discussed in from the design phase to the actual implementation on a target m. There are 17 case studies given in this book on various systems you may encounter in day-to-day life. Overall the hardware and are developed in this book can be reused for any embedded sys- project and is expected to act as a rapid prototyping unit for the dded systems industry. sons for Proposing this Book e market is flooded with a number of good books on embedded sys- designed especially with the most popular MCS-51 family. These are traditional in nature, i.e., they start with the routine archi- ral features of 8051, description of registers, ports, interrupts, etc. of these are already covered in the device data sheet and appli- n notes. In the present book all such routine features are skipped. ocus is on programming microcontrollers to be specific MCS-51 rce like port, time/counter, interrupt, serial I/O, etc. Rather than ducing the underpinning theory or reproducing lengthy data sheets, pproach is “learning-through-doing” and one that appeals to busy onics designers. The ‘C’ codes given are well supported by easy-to- stand comments wherever required. Mastering the basic modules ands-on working with the projects will enable the reader to grasp asic building blocks for most 8051 programs. Whether you are a nt using the MCS-51 family of microcontrollers for your project or an embedded systems programmer, this book will give you a tart in using and understanding the most popular microcontroller. thors through their interaction with the undergraduate and post- ate students as well as industry professionals have found that such k is the need of the microcontroller community interested in C amming. The book will bridge the gap between the microcontroller ware experts and the C programmers. or Features e objective of this book is to introduce the readers to the design mplementation of an embedded system. It covers the unique require- and limitations of operating in an embedded environment. It also s microcontrollers as the most widespread example of embedded ms. In particular, it focuses on the MCS-51 family of microcon- rs, their programming in C language, and interfacing techniques. ecial emphasis is to provide hands-on experience for the readers a hardware and interfacing modules described in this book. The s to empower the reader to actually solve his or her problem with ctical hands-on pedagogy through the hardware and software pre- d in this book. The principle of “Design Reuse” is explained effec- ther, the readers will also learn how to follow the sequence of data hrough the microcontroller when a program is executed. Addi- ly, the readers will learn the operation of the microcontroller’s unctions and the external devices driven by the microcontroller. ware and software design issues are discussed for specific systems mented using MCS-51 as the embedded microcontroller. would like to take the opportunity to thank all those who have buted or helped in some way in the preparation of this text. cular thanks must go to our heads of the institutions – Professor Salunkhe, Vice Chancellor, Shivaji University, Kolhapur, India, Professor P.S. Zacharias, Vice Chancellor, Goa University, Goa, – for the encouragement and support. We would also like to Mr. P. Venugopal, Director, Software Technology Parks of India, rashtra Region, for his support. Dr. Kamat and Dr. Naik would o thank their respective wives for their understanding and patience n when the preparation of the book took time which could have spent with the family. Our thanks then to Kamat’s wife Rucha Naik’s wife Deepa. ditionally, Mr. Shelake and Mr. Parab would like to express grati- o their parents for their encouragement and support over the years. t would like to dedicate his contribution to this book to the mem- the late Professor G.G. Tengshe and the late Dr. V. Rao Indolkar, Machine Control Tools Ltd., Mumbai. Kamat would also like to thank to his teacher in this field . Ramgopal, Indian Institute of Science, Bangalore, and Dr. Senthil ar, Dr. Raghurama, Deputy Director (Academic) of BITS Pilani ll as Mr. K.S. Deorukhkar for help in reviewing and critical sug- ns. The past batches of M.Sc. Electronics students of both Shivaji rsity and Goa University especially Mr. Roy, Mr. Rupesh from m Computers must be thanked for generation of problems for ams developed in this book. Jivan S. Parab Vinod G. Shelake Dr. Rajanish K. Kamat Dr. Gourish M. Naik xv pter 1 rocontrollers: Yesterday, Today, Tomorrow Defining Microcontrollers s said that from the definition everything true about the con- ollows. Therefore, at the outset let us take a brief review of how l-pervasive microcontroller has been defined by various technical es. microcontroller (or MCU) is a computer-on-a-chip used to con- lectronic devices. It is a type of microprocessor emphasizing ufficiency and cost-effectiveness, in contrast to a general-purpose processor (the kind used in a PC). A typical microcontroller con- all the memory and interfaces needed for a simple application, as a general purpose microprocessor requires additional chips to de these functions. . . .(Wikipedia [1]) highly integrated chip that contains all the components compris- controller. Typically this includes a CPU, RAM, some form of , I/O ports, and timers. Unlike a general-purpose computer, which ncludes all of these components, a microcontroller is designed for y specific task – to control a particular system. As a result, the can be simplified and reduced, which cuts down on production . . . (Webopedia [2]) {microprocessor} on a single {integrated circuit} intended to ope- s an {embedded} system. As well as a {CPU}, a microcontroller ally includes small amounts of {RAM} and {PROM} and timers /O ports. . . .(Define That [3]) single chip that contains the processor (the CPU), non-volatile ry for the program (ROM or flash), volatile memory for input and t (RAM), a clock and an I/O control unit. . . . (PC Magazine [4]) microprocessor on a single integrated circuit intended to operate embedded system. As well as a CPU, a microcontroller typically des small amounts of RAM and PROM and timers and I/O ports. OLDOC [5]) 1 rab et al. (eds.), Exploring C for Microcontrollers, 1–18. Springer. he crux of the matter is the widespread uses of microcontrollers ctronic systems. They are hidden inside a surprising number of ucts such as microwave oven, TV, VCR, digital camera, cell phone, orders, cars, printers, keyboards, to name a few. e last three decades and especially the past few years have wit- d the tremendous growth in the top-of-the-line processors used rsonal computing and digital signal processor (DSP) applications. y, the use of microcontrollers in embedded systems outnumbers se of processors in both the PC and the workstation market. It is ated that over 50% of the vast majority of the computer chips sold microcontrollers. The main reasons behind their huge success are rful yet cleverly chosen customizable electronics, ease in program- and low cost. These days microcontrollers find increasing appli- n even in areas where they could not be used previously. With the asing costs and footprints, it is now possible to have small-sized ost-effective microcontroller units (MCUs) for new applications. microcontrollers today are small enough to penetrate into the tra- al market for 4-bit applications like TV remote controls, toys, and s. For the simplest of all control applications they can offer high smart switch functionality for applications that previously used omechanical devices. Also the customers now can add intelligence eir end products for low cost as per the microcontroller market t by Frost & Sullivan research service [6]. Eagle’s View: Microcontrollers and Other Competing Devices nerally the technical fraternity try to compare the various devices microprocessors, PCs, microcontrollers, DSPs, and reconfigurable es like FPGAs and CPLDs. An interesting point to note is that dded systems are made using all the above-mentioned devices t PC owing to its general purpose architecture. As programma- is the common feature of all these devices, they have their firm g in different application domains. On one side of the spectrum, controller-based embedded system design emphasizes on task- ic dedicated applications at low power, low cost, high through- and highest reliability. On the other extreme of the spectrum, A-based embedded systems dominate their custom computing ectures. Unlike microcontrollers, these systems can be reconfigured e fly to suit the application with higher computational density and ry required to store their configurations. e technical community also tends to associate various character- of embedded systems with microprocessors and microcontrollers. microprocessors are typically found to dominate the desktop arena ng on more and more bit processing capability, with other fea- such as fairly good amount of cache with memory management rotection schemes supported by the operating system. Although controllers share flexibility aspect of microprocessors through pro- ming, 8-bit versions are more in use (although 16- and 32-bit exist) RAM and ROM (instead of cache) added with many on chip herals like timer/counter, decoder, communication interface, etc. literature many embedded systems products have been reported as processors. On the other side of the processor spectrum, a DSP pos- special architecture that provides ultra-fast instruction sequences, as shift and add, multiply and add, which are commonly used in intensive signal processing applications. The common attributes ated with the DSPs are multiply-accumulate (MAC) operations, pipelining, DMA processing, saturation arithmetic, separate pro- and data memories, and floating point capabilities required most time. However, the line of differentiation between all these devices ting blurred at a rapid pace. With the introduction of fuzzy logic, ial intelligence and networked communication capabilities in the mer products like refrigerators, mobile phones, and cars, conver- of the architectures of most of the above-mentioned programmable es is witnessed by the industry. Today’s ideal microcontroller is ted to offer plenty of MIPS, run the DSP programs with the same of the DSP processor, integrate all its peripherals and support communicate with the world with I2C or CAN protocols, with- extremes of environment in a car engine, and cost but a few Vignettes: Microcontrollers s interesting to note that the development of microprocessors seems an accident out of the microcontroller synthesis. In 1969, Busicom, anese company, approached Intel to convert their special pur- ROM and shift register–based calculator cores into a specialized ation specific processor. The objective was the development of controllers rather than a general purpose of CPU chips for key- scanning, display control, printer control, and other functions for andom logic chip-set originally envisioned by Busicom. The four ns [7] proposed by Federico Faggin, Ted Hoff, and Stan Mazor from were a 2048-bit ROM with a 4-bit programmable input/output (4001); a 4-registers × 20-locations × 4-bit RAM data memory a 4-bit output port (4002); an input/output (I/O) expansion chip, ting of a static shift register with serial input and serial/parallel t (4003); and the 4-bit CPU chip (4004). The 4001, 4002, and are very close to microcontroller kind of architecture rather than processor. However, the Intel 4004, which was supposed to be the s of a calculator, turned out to be a general-purpose microproces- powerful as ENIAC. The scientific papers and literature published d 1971 reveal that the MP944 digital processor used for the F-14 at aircraft of the US Navy qualifies as the “first microprocessor”. ugh interesting, it was not a single-chip processor, and was not al purpose – it was more like a set of parallel building blocks you use to make a special purpose DSP form [8]. It indicates that ’s industry theme of converging DSP-microcontroller architectures tarted in 1971. e other companies were also catching up at the same time. The official claim of filing the patent goes to Texas Instruments under ade name TMS1000 way back in 1974. This was the first micro- oller which included a 4-bit accumulator, 4-bit Y register and 2- or X register, which combined to create a 6- or 7-bit index register e 64 or 128 nibbles of on-chip RAM. A 1-bit status register was used rious purposes in different contexts. This microcontroller served as rain of the Texas Instrument’s educational toy named “Spark and ” shown in the movie ET: The Extraterrestrial. In 1976, Intel intro- the first 8-bit microcontroller family MCS-48 which was so pop- hat they could ship 251,000 units in that year. After four years of nuous research, the MCS-48 family was upgraded to 8051, an 8-bit controller with on-board EPROM memory. Intel shipped 22 million in 1980. The market requirement was so much that the total units n three years later were 91 million. The year 2005 is a special one e microcontroller 8051. It has celebrated its 25th anniversary. But, n 2005, Intel notified they would discontinue all automotive versions ir microcontrollers, including 8051. Car engine control units were perhaps the most prominent application for 8051s. This means only hing, Intel gives up the microcontrollers for good. This is confirmed oduct change notification published in early 2006, announcing that drops its whole microcontroller business [9]. ing 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 tomobile industry is the main driving force in propelling the growth crocontrollers. It is estimated that the microcontrollers constitute of the semiconductors used in a vehicle [10]. Requirements of the mobile sector has forced the microcontroller manufacturers to come ith the new bus protocols such as control area network (CAN) ocal interconnect network (LIN). Microcontrollers of all bit cores sed in vehicles according to the Frost & Sullivan Industry report. 8- and 16-bit microcontrollers are used for low-end applications ower-cost vehicles while the 32-bit microcontrollers are used for end application and high-end vehicles. It is estimated that cur- 30–40 microcontrollers are used in low-end vehicles and about crocontrollers are used in high-end vehicles. These requirements ntinuously increasing and it is highly likely that the count of micro- ollers in vehicles will further increase in the future, quotes World controllers Market Report by Frost & Sullivan [10]. Figure 1.1 Microcontroller application tree nsmission is no longer required because a lower-cost AC induction uctance motor controlled by sophisticated microcontroller-based onics can provide all the normal machine cycles [11]. Additionally, ectronically controlled induction or reluctance motor provides a effective and gentler agitation (wash) cycle that allows the drum ining the clothes to be rotated first in one direction, then stopped, otated in the opposite direction without requiring any additional anical device. This forward/reverse agitation cycle provides a more ve means of cleaning your clothes without damaging the fibers to make them. s also observed that the induction of microcontrollers in a product creased the market demand of the product itself. One such exam- NEC Electronics’ 8-bit microcontroller [12], which is employed in half of the digital cameras produced throughout the world, thus ng it a hit product – albeit one that plays its role behind the scenes. 03, the shipment volume of 8-bit microcontrollers for digital cam- e achieved monthly shipments of two million. Currently, the most only used microcontroller for digital cameras is the µPD78003×. ndustry’s top-level, low-voltage (1.8 V) A/D converter is built his compact 64-pin QFP package with an edge measuring a mere 10 mm. Growth Economics ny industry analysts have reported a bright growth economics icrocontroller in the near future. Bourne Research reports that S-based motion, pressure, and acoustic sensors (as well as other generation sensing technologies) are not only finding their way into c consumer products like toys, housewares, sporting goods, and ng, but applications as far-reaching as flooring materials, medical ostics, retail fixtures, and vending machines. System complexity is s varied, but Bourne Research notes that, more often than not, products will utilize multiple sensors and microcontrollers [13]. her interesting report by the Semiconductor Industry Association reveals that the microcontroller sales are projected to grow by to $12.3 billion in 2006 and to $15.4 billion in 2009, a compound an- rowth rate (CAGR) of 6.3% [14]. The positive growth economics of controller chips also ushers the associated growth of software such mulators, cross compilers, and assemblers. The market is witnessing novel supporting software packages with simple user interface with nient compiling and debugging tools. 1.1 Major players in the microcontroller market. (From 2006 EDN Directory of Microprocessors and Microcontrollers) ny Product range Application domain Core8051 8-bit-microcontroller IP Consumer, communications, auto- motive, industrial, and military/ aerospace applications Nios II/f (fast), Nios II/e (economy), Nios II/s (standard), Soft IP cores Automotive, consumer, industrial, medical m Royalty-free, 8- and 32-bit, FPGA-based soft processors, and FPGA-independent TSK3000RISC core Automotive, industrial, communications, and computer-peripheral g s ADuC7128 family of precision analog microcontrollers; ADSP-BF561 Blackfin ADSP-BF534 Blackfin, BF539 with CAN Audio, automotive, communication/wired, consumer, industrial, imaging and video, medical, motor control, security d ts Embedded PowerPC proces- sors PPC405CR PPC405EP, PPC405EZ, PPC405GP, PPC405GPr, nP405H, etc. Communication/wired, computers and peripherals, consumer, industrial, imaging and video, medical, mobile/wireless, motor control, security nter- al Two configurable, 32-bit processor-core families ARC600 and ARC700 Sound advanced subsystems targeting portable media devices and advanced-definition audio applications Range of processor cores, including the ARM7, ARM9, ARM10, and ARM11 families and the new Cortex family featuring Thumb-2 technology Audio, automotive, communication/wired, computers and peripherals, consumer, industrial, imaging and video, medical mobile/wireless, security AVR, AVR32, ARM7, ARM9, 8051, Teak, and Diopsis DSP cores Consumer, computer/networking, communications, security/smart cards, automotive, industrial, medical, military, and aerospace applications including 8051 cores with instruction execution one clock per cycle; configurable 8051, 8-bit Z80 and 16-bit 68000 compatible devices wired, computers and peripherals, consumer industrial, imaging and video, medical military/aerospace, mobile/wireless motor control Logic ARM9- and ARM7-based embedded processors EP9301, EP9302, EP9307, etc. Audio and industrial markets Semi- tor Four microcontroller families targeting networked, secure, mixed-signal, and 8051 drop-in designs 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 ale n- Ultralow-end, RS08-based, 8-bit microcontrollers to an advanced 32-bit ColdFire core Mobile and videoconferencing phones, portable media players, PDAs, and portable GPS applications, networking, home and SOHO (small-office/home-office) networking, automobile nics ca 32, 16, and 8-bit microcontrollers with onboard-flash, ROM, ADC, DAC, CAN (controller area network), USB, and LCD controllers Automotive, communications, computer peripheral, industrial, and consumer applications n lo- 8-, 16-, and 32-bit bit XC886/888, XC164CM TC116× Industrial and automotive, industrial motor control, building control for lifts and escalators, intelligent sensors, distributed I/O modules, and industrial automation n- 8-bit microcontrollers, including the 8051 and PIC, through its partners, Cast and Digital Core Design, LatticeMico8 an 8-bit soft microcontroller core Automotive, communication/wired, computers and peripherals, consumer industrial, medical ary ARM Cortex-M3-based microcontrollers Industrial and motor control hip logy 8- and 16-bit PIC microcontrollers, as well as 16-bit dsPIC DSCs (digital signal controllers) Motor control and general purpose ny Product range Application domain al on- COP8 flash microcontrollers featuring an 8-bit core with 32 kbytes of onboard flash 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 onics ca 8-bit uPD78F0711 and uPD78F0712 flash-based microcontrollers, 32-bit flash-based V850ES/IE2 series Consumer appliances, home health care, building management systems and industrial controlled applications Architectural Trends e emerging trends in microcontroller architecture are dictated by echnological needs of the embedded system applications. In gen- he common road map is characterized by the features like single onal, tightly constrained in terms of cost, power, speed, and foot- as well as continuously reactive in a real-time manner. The micro- oller world is divided over the architecture used. Controllers like 68HC11 join their microprocessor counterparts (80× 86 family) in Von-Neumann architecture by sharing RAM and program mem- ith the same bus. This imposes the same bit width for the buses ective of their requirement, which is not the case with the PIC ssors which uses Harvard architecture. t Treads on MCU Turf s really interesting to note that in this era of 32-bit processors, -bit microcontrollers are flourishing and enjoying a stable future. easons behind this are low cost and inexpensive development soft- An 8-bit microcontroller like 8051 today enjoys 40% of the market [15]. It has become so popular that about 40 manufacturers now it with 800 derivatives used for diverse applications right from bit CPU optimized for event control, Boolean processing, on-chip ry (up to 32 K) and on-chip peripherals (timer/counters, serial PCA, etc.). The other manufacturers like Atmel, Dallas, Philips, g Devices, etc., have extensively worked for strengthening the basic y introducing additional features such as Additional Data Pointers R), Extended Stack Space, Fast Math Operations and Extended duced Instruction Sets to name a few. Table 1.1 summarizes the es of the popular 8051 derivatives manufactured by various compa- Although industry analysts predicted the saturation of 8051 family lso its death, it turned out to be a rumor. In 2003, Cygnal released ’s highest performance 8051 microcontroller [16]. The C8051F120 y devices include 128 Kbyte Flash memory, 8448 byte RAM, and ackaged in either a 100-pin or 64-pin TQFP. On-chip peripherals de a 12-bit 100 ksps ADC, two 12-bit DACs, a 2% internal oscillator, erature sensor, voltage reference, two UARTs, and many features DSP processor. Power Design e latest 8-bit devices continue to drive up the performance bar simplicity for usage and ease of programming. Most of these de- are aimed at low power consumption achieved by using sleep modes he ability to turn certain peripherals on and off. The best example is is XE88LC02 from XEMICS [17], a recently launched microcon- r, which features programmable gain/offset amplifier followed by resolution ADC with four differential or seven pseudo differential s, with current consumption as low as 2 µA in real-time clock mode typical 300 µA/MIPS in sustained computing mode. Recently, l has also strategically evolved their microcontroller architecture by menting novel power saving techniques. Atmel’s picoPower tech- y uses a variety of techniques that eliminate unnecessary power mption in power-down modes. These include an ultra-low-power z crystal oscillator, automatic disabling and re-enabling of brown- etection (BOD) circuitry during sleep modes, a power reduction er that completely powers down individual peripherals, and dig- nput disable registers that reduces the leakage current on digi- puts [18]. PicoPower microcontrollers consume down to 340 µA in mode, 150 µA in idle mode at 1 MHz, 650 nA in power-save mode 00 nA in power-down mode. d in the 1970s with MP944, which had more of DSP orienta- For a microcontroller engineer to consider a DSP or for a DSP eer to use a microcontroller, three strict criteria must be met: /performance, peripheral set, and development tool quality [19]. trend is now more pronounced as seen in the newly launched controller cores by Motorola. For instance, in its 56F83xx family crocontrollers, Motorola has introduced a series of devices that it ds to meet uprated processing needs in today’s systems – partic- in automotive systems – while keeping 8/16-bit economics and ing the shift to 32-bit controllers. The defining features of the e series are the inclusion of some DSP attributes and the use of ip flash memory instead of EEPROM. The term “hybrid” describes evices’ combination of microcontroller and DSP functions. These es are not hybrid in the sense that they combine twin processing rather, they add the facility to efficiently execute certain DSP- rithmetic functions such as multiply-accumulate operations [20]. kinds of architectures are in heavy demand owing to such hybrid processing requirements in application domains such as speech ssing in consumer applications. The key challenges in converging two diversified architectures are combining the pipelining, register ed, complex conditional resolving architecture of microcontrollers the multiply-accumulate, data massive, and deterministic software ally with zero overhead loops of the DSPs. With the inclusion of functionality in microcontrollers many things such as modem sup- compression of data voice, and image as well as filtering and speech esis/recognition are possible. This has been successfully done in of the recently launched microcontrollers like Goal Semiconduc- VMX1016. This microcontroller possesses a powerful hardware metic unit with 32-bit barrel shifter that can perform simultaneous signed multiplication and 32-bit addition. Another example of onvergence is Hitachi’s SH3-DSP based on a single instruction m approach combining general purpose CPU and dedicated DSP onality in a single architecture [21]. These types of microcon- rs facilitate upgradation of the embedded systems merely with the on of software utilities. den Debugger th the increasing design complexity debugging or verification has me the major bottleneck to meet the tight time to market schedule. bility by embedding test points or scan chains as well as exter- ebugger are on the way of extinction. The new microcontrollers ruggling to sort out the resource requirement vs computational exity dilemma. The use of logic analyzer for monitoring the clock y as well as the bus activity has become very expensive and many physically impossible with the shrinking footprint of microcon- rs operating at the clock speed as high as 100 Mhz. The IEEE-ISTO s 5001 Forum which comprises around 25 major microcontroller facturers defines a common set of on-chip debug features, proto- pins, and interfaces to external tools which may be used by real-time dded application developers. As a result, more than 70% of leading dded microcontroller vendors now have dedicated circuits and pins, assist in new product development based on the IEEE 1149.1 Joint Action Group (JTAG) 4-wire serial interface [22]. Apart from the G interface, today’s microcontrollers are enriched with the back- d debug mode (BDM) and on-chip emulation being achieved at r abstraction level for reducing size and searching space in the ging. Although the microcontroller community is still far from menting the debugging solution for pointer problems, accessing alized memory, and interprocess interaction, the chips are domi- with single stepping and breakpoint utilities, e.g., the recently hed C8051F120 [23] has on-chip debug circuitry facilitating full- in-system debug features such as single-stepping, breakpoints, and ying registers and memory. b-Enabled Microcontrollers bedded internetworking allows anytime, anywhere, control of the ct with a regular self-maintenance and pervasive, wearable com- g. The tangible benefits of Internet connectivity in products like nditioner or washing machine are self-upgradation by downloading oftware updates, lowering cost by fine-tuning energy consumption ak hours, generating auto maintenance alarms, etc. Microcontroller facturers have come out with new processors having a built-in ility to cope with the challenges of web processing. Dallas Semi- ctor has come out with the microcontrollers that can directly serve b pages. TINI (Tiny InterNet Interface) [24] is a microcontroller- development platform that executes code for embedded web s. Remote devices can have preferences and settings adjusted from just by having their administrator browse a web page hosted by xposes the extensive I/O capability of the Dallas microcontrollers. va programmer accesses the I/O from robust APIs (Application am Interfaces) that include Ethernet, RS-232 serial, I2C, 1-Wire CAN, and memory-mapped parallel bus. By using these APIs, ammers code functions without worrying about the underlying ace to hardware peripherals. The runtime environment is tightly for optimized network communications and efficient device I/O ghput. minance of Soft IP cores/Free Microcontroller? e new VLSI devices such as FPGAs offer several advantages microcontrollers. FPGA-based platform enables the developer to thanks to the JTAG philosophy) and add features in parallel ut the need for repeating the complete testing of the platform again. Increasing number of manufacturers are now offering the A-based microcontroller core. The list of FPGA-based soft IP cores 051-based microcontrollers is available at the web page of Keil //www.keil.com/dd/ipcores.asp). For example, the C-8051 core is DL model of the Intel 8-bit 8051 microcontroller by Aldec Inc. [25]. model is fully compatible with the Intel 8051 standard and is avail- n both EDIF and VHDL netlists formats. The EDIF netlist is used e place and route process and VHDL is the post-synthesis netlist for the simulation only. Both netlists are technology-dependent se they are created after the synthesis where the customer needs ecify a vendor, target family, etc. Even the source code of a set of testbenches for the cores is also available. Jump Starting Your First Embedded System Project ure 1.2 shows a minimum setup required to build microcontroller- embedded system project. The foremost requirement is a low- PC pre-loaded with the IDE to facilitate the code development, ation and testing before actual dumping the code in the flash of the controller. The Keil IDE is covered in depth in Chapter 2. Most of rojects developed in this book have been tested on AT89S52 which he following features: 8K Bytes of In-System Reprogrammable Flash Memory Fully Static Operation: 0 Hz to 33 MHz e 1.2 Minimum setup recommended for your Embedded System Laboratory Three-level Program Memory Lock 256 × 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 Power-off Flag Fast Programming Time Flexible ISP Programming (Byte and Page Mode) Execution of Embedded System Project: Is it a Gordian’s Knot? re is a piece of thought for the student community as well as preneurs looking for a successful embedded system project. ject Idea to Execution successful project development, first you must develop an idea. are lots of sources for idea generation. Ideally your ideas should from research laboratories towards the marketplace. Many devices rocesses around can be improved by the inculcation of microcon- rs. The automation of the nylon rubber stamp making machine bed in the case studies is the best example. The thinking should y go on the following lines: How can the process be controlled a microcontroller, ultimate efficiency, or throughput improvement embedding of microcontrollers? Are there any simulation tools to l and estimate before the actual experimentation? In what way he process be made more intelligent (or thinking) by using the mi- ntrollers? For answering the automation of a process plant using controller, one must think about the on-chip resources and their ive usage (e.g., interrupt level/edge, usage of ports, timer/counter, o on). The answer to the second question should throw light on enefits of using the microcontroller in your project. (Can you think een house controller without microcontroller? Or the amount of y saved with the microcontroller-based corridor lighting which is mented in the case studies.) According to the US Department of gy [26], the electricity used to light businesses represents 25% of the y they spend; so it is important to develop energy-saving devices. a simple switch equipped with photosensor and microcontroller can o reduce lighting energy consumption by 30%. mulation is the best methodology to avoid project failure as well work in a time-efficient manner. It is always a good idea to simu- he things using the microcontroller IDE instead of rushing to the ct board and actually dumping the code in the on-chip memory. project. The last question is little challenging. In order to make microcontroller think or make it intelligent you have to resort to novel items such as neural net implementation, extrapolation, and tical techniques. the sole success of the embedded system project is on firmware, the are and the underlying hardware should not be treated as separate es. Therefore, the term “Hardware–Software Co Design” has gained f significance in the field of embedded systems. Following issues ning to hardware and software are of utmost importance while ting any embedded system project. dware and Software Issues en the simplest things dictate the final specifications of the final ct. There is often a major gap between the theory of design and “plays” in the real world. The most casual thing for a designer in microcontroller-based product is the value of the crystal frequency is 11.0592 MHz. The rationale behind this value is the ease of ency division to yield exact clock rates for standard baud rate gen- n for the UART. However, in the applications where the serial unication is not at all in picture, the designer has lot of flexibil- choosing the crystal value. The crystal value decides the execution , e.g., Intel 8051 microcontrollers require a minimum of 12 oscillator . This means if the crystal is of 12 MHz, then 8051 microcontroller at performance of 1 MIPS. If a thorough analysis of the occurrence l-time events reveals that this speed is not required, then a designer go for a lower value of the crystal. The ultimate advantage is a cant reduction in power consumption. In CMOS-based versions of a linear relation between oscillator frequency and power consump- xists. Another lower range crystal value is 7.3728 MHz which can ed even for standard baud rate generation. The notable thing is: counter1 of 8051; this gives an even 38.4 Kbps rate exactly, which possible even with 11.0952 MHz Xtal. The lower crystal value also es to access low-speed peripherals and frees the system from elec- gnetic interference (EMI) evident in high clock speed MCUs. oblems such as reset, latch-up, memory corruption, and code run- are found to fail the embedded system application due to ESD MI. Areas of MCUs typically vulnerable to ESD and EFT stresses de: power and ground pins, edge sensitive digital inputs, high fre- y digital inputs, analog inputs, clock (oscillator) pins, substrate g proper package style, footprint, and maximum number of supply round pins [27]. hile developing the software it is important to have a modular app- . The interrupt service routines should be as short as possible to e the interrupt latency. Readability and debugging specifications nly enhances the value of the software but also frees the novice nimize the learning curve. Choice of the language plays an impor- role to decide the lead time, life and processor migration of your controller-based product. Using the higher level languages like ‘C’ riting programs offers some unique advantages such as faster devel- nt, improved portability, reusability, platform independence – all duced cost. Complex algorithms can be very easily implemented in ther than assembly. As the design evolves in due course, the req- restructuring of the program without breaking the existing design e easily done in ‘C’. Although assembly language is the best choice me critical programs, the user face lot of difficulties in managing programs especially in memory allocation. “Porting” the assembly age code to another processor family is almost impossible or very ult. pter 2 egrated Development Environment egrated development environment popularly known as IDE is a of software tools that facilitates microcontroller programming. The DE enables the embedded professional to develop the program in d assembly as well. The IDE passes through the source code to the syntax. The compilation leads to a hex file to be dumped in microcontroller on-chip ROM. A quick session of simulation and ging using the IDE ensures the working of the program before- The user can verify the results as the package presents screenshots chip resources. This chapter presents in-depth discussion on using Vision 2 package of Keil IDE on MS Windows platform. It is mended that while going through the discussion the user should the µVision 2 package of the Keil. A step-by-step working as sed in this chapter will empower the user to get familiar with eil IDE. Getting Familiar with the IDE e microcontroller product development cycle consists of several 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 microcontroller-based project generally makes several iterations gh the above-mentioned steps before it sees the light of the day. 19 rab et al. (eds.), Exploring C for Microcontrollers, 19–28. Springer. for microcontroller application development is refereed to as IDE. examples of the popular IDEs apart from Keil are MPLAB from chip, PE micro from Motorola, and AVR studio from Atmel. y typical IDE comprises many subcomponents such as a text editor tering the code, building tools for converting the code into machine compiler to convert ‘C’ code to assembly or hex format, and linker ovide absolute addresses to the relocatable object code. The IDE is ally equipped with powerful code simulator that models operation e target microcontroller as code execution is in process. IDEs are ble as a software suite which runs on a stand-alone PC and displays llows to modify the contents of virtual I/O and on-chip resources as registers. Single-stepping and breakpoint facilities are provided tematically execute and watch the cause/effect relationship of the A provision of instruction cycle calculation/display is also provided to see the time/memory efficiency of the code. Working with Keil IDE the entire software development described in this book is based e Keil 8051 Development Tools, it is worthwhile to study the tool pth. The Keil IDE is a user-friendly software suite to develop your ode and test the same in a virtual 8051 environment. The main re of the Keil is that it allows C programmers to adapt to the 8051 onment quickly with little learning curve. offers the designer a device database of MCS-51 family from which arget device of interest can be chosen. The µVision IDE sets the iler, assembler, linker, and memory options for the designer. The comes with numerous example programs to assist the designer to his project. With the virtual environment, the available on-chip rces of the microcontroller chosen can be seen working on the PC n. The simulation window facilitates very realistic simulation of CPU and embedded peripherals. The graphical window shows the and configuration of the embedded peripherals and displays the ction of the microcontrollers with external peripherals. Although mulation exercise consumes time, it helps to save the bugs and ct failure in the long run. natural question that occurs to designer is in what way the ntional C programming for PC is different from the C programming Keil or C51 programming. The basic objective of the conventional to registers. However, unlike the conventional C program- on PC, most of the microcontroller-based embedded systems ations demand reading and setting or resetting of single bits, oolean processing. The second main difference is the program- environment. Conventional C operated under the umbrella of an ting system may be Linux or Windows, wherein there is a pro- of system calls the program may use to access the hardware. st all the programs written with microcontroller are for direct here the while(1) loop is common. The above-mentioned differ- are bridged in Keil compiler by adding several extensions to language, e.g., connecting of interrupt handlers. A good web- rces are available on this topic at www.massey.ac.nz/∼chmessom/ ter%206%20C%20ProgrammingFinal.pdf Development Flow for the Keil IDE e evaluation version of the Keil IDE for MCS-51 family (also n as C51 evaluation software) can be downloaded from the website keil.com. One can go up to a limit of 2 Kbytes of object code the evaluation version. Once the Keil IDE is installed, a short cut rs on the desktop. p 1: Interfaces Offered by Keil IDE er clicking on the above shown shortcut the following steps d be carried out. The first blank window will appear as shown ure 2.1. u will be working with three windows presented by the Keil IDE. irst is target toward the extreme left of the screen which is blank e moment, but will be updated as you go on working with the ct. The source file, register header file, and the target microcon- r chosen is displayed here. The bookmarks for the user such as sheet, user guides, library functions, etc., forms a ready reckoner e developer. The program window which occupies most of the size r screen displays the source code in C. At the lowermost end of the n, an output window is presented which gives information regarding rors and other output messages during the program compilation. en a new text file for writing your source code. This file has to be with .c extension. This source code file will be ultimately added Figure 2.1 The starting interface of Keil IDE your project to be opened as per step 2. The addition should be as per the instructions given in step 5. p 2: Opening a New Project re you can give a meaningful name for your project. After saving it reate a folder which will store your device information and source register contents, etc. Figure 2.2 shows a project opened with a trial. p 3: Selecting a Device for the Target er completing step 2, Keil will give an alert to select the device. µVision 2 supports 45 manufacturers and their derivatives. In the se given in this book we have selected Atmel’s 89S52 microcon- r as a target. p 4: Copying Startup Code to Your Project e “startup.a51” will be added automatically to your project from eil library “c:\keil\c51\lib” to [c:\keil\c51\EXAMPLES\HELLO\ \STARTUP.A51]. Figure 2.2 Opening a new project Figure 2.3 Selecting a device for the target Figure 2.4 Copying startup code to your project p 5: Adding Your Program Source Code 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” serve the files getting updated in the target window. You will have uble-click on the C source file name displayed in the target window w it. p 6: Configuring and Building the Target ght click on target 1 in the target window, select the option for t 1, a window to choose the options for the target will be displayed. you can choose the microcontroller frequency, listing of files, output x, debug information, etc. e important point here is choosing the appropriate memory model. Figure 2.5 Adding your program source code per the on-line Keil IDE manual [28] C51 currently supports the ing 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 8051’s internal memory. COMPACT: variables are stored in paged memory addressed by ports 0 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. Figure 2.6 Configuring and building the target Table 2.1 Choosing the best memory model for your C51 program RAM supported Best for Worst for Total RAM 128 bytes (8051/31) Code size up to 4K Global variable (be kept minimum) act 256 bytes off-chip, 128 or 256 bytes on-chip High stack usage, pro- grams with large num- ber of medium speed 8-bit variables Rarely used in isolation, usually combined with the SMALL switch reserved for interrupt routines. 64 KB, 128, or 256 bytes on-chip Easiest model to use 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 0×FFFF. Within each 64 KB memory block a COMMON area must be set aside for C library code. Inter-bank function calls are possible. Figure 2.7 Compiling your program by pressing F7 p 7: Compile Your Program by Pressing F7 her press F7 or click on build target in the target window to compile program. The output window will show the errors or warnings if You can also see the size of data, code, and external data, which is mense importance since your on-chip memory is limited. p 8: Working in Simulated Mode ce the program is successfully compiled, you can verify its func- ity in the simulated mode by activating the debug window. For ress CTRL + F5 or go to the menu option “Debug” and select t and Stop Debug Section”. Press F11 for single stepping or F5 ecution in one go. Go to the menu item “Peripheral” and select ppropriate peripherals to view the changes as the program starts ting. minating the debug session is equally important. Click on “stop ng” or ESC key to halt the program execution. You can make hanges to the program after coming out from the debug session Figure 2.8 Simulation mode of Keil ressing start/stop debug session. Few iterations through the -mentioned process will make your program completely bug-free ave your time and other resources on the actual hardware. p 9: Actual Dumping of the Code Microcontroller’s On-chip Memory ere are different mechanisms for this. Some programmers use ready- programmers to program the microcontroller. If you are interested rchasing one for your project, the list is enclosed. Design of vari- rogrammers has also been given at Wichit Sirichote’s webpage at //www.kmitl.ac.th/∼kswichit%20/. pter 3 of C Programming for Microcontrollers ere are large number of textbooks and data sheets which give erview of 8051 architecture, pinout, and other peripheral details. ver, with the Keil IDE, you can take the benefit of the header and need not remember the details like the port address, timer er addresses, etc. The CA51 Compiler Kit for the 8051 microcon- r family supports all 8051 derivatives including classic devices and res from companies like Analog Devices, Atmel, Cypress Semicon- r, Dallas Semiconductor, Goal, Hynix, Infineon, Intel, OKI, Philips, n Labs, SMSC, STMicroelectronics, Synopsis, TDK, Temic, Texas uments, and Winbond. Familiarizing with Your Compiler Capabilities e C for microcontrollers and the standard C syntax and seman- re slightly different. The former is aimed at the general purpose amming paradigm whereas the latter is for a specific target micro- oller such as 8051. The underlying fact is that everything will be ately mapped into the microcontroller machine code. If a certain e such as indirect access to I/O registers is inhibited in the target controller, the compiler will also restrict the same at higher level. arly some C operators which are meant for general purpose com- g are also not available with the C for microcontrollers. Even the tors and constructs which may lead to memory inefficiency are not ble in C programming meant for microcontrollers. Be aware that rget code should fit in the limited on-chip memory of the proces- ven the I/O functions available in standard C such as printf() or ) are either not made available in C compilers for microcontrollers vised not to use them. These functions eat up lot of memory space re not time-efficient owing to the dragging of supporting func- like floating point routines and lot of delimiters. Another striking ence in case of embedded systems programs is that they do not 29 rab et al. (eds.), Exploring C for Microcontrollers, 29–36. Springer. n traditional C. e C for microcontrollers is more closer to the assembly language the conventional or traditional C. Few examples to support the statement are presence of arithmetic/logic/bitwise operations to ble machine operations, Use of pointers which corresponds to mem- ccess at machine level etc. The detailed information regarding the res of ‘C’ supported may be found in the document C×51 Compiler s Guide for Keil Software [28]. Whether to Use Headers or Not? a professionally embedded systems developer one can write a stand- ‘C’ code, requiring no header files, and it will compile correctly with eil C51 compiler. However, this requires a through study of the tar- microcontroller architecture. With the large number of derivatives e 8051, it is difficult to remember the on-chip resources, e.g., the 51 versions from Atmel such as AT89C2051 or AT89C51 have two s while the other members such as At89C52 or AT89S53 have three s. Therefore, although there is little memory space overhead, it is able to use the header files which defines all the on-chip resources e target microcontroller, e.g., whenever you choose the target de- uch as AT89C52, Keil IDE gives the information regarding all its ip resources in the window at the right side as shown in Figure 3.1. u can observe another advantage of working with the header file. e the header file <REG51.h> or <REG52.h> in the program win- and select the target device as 80C51. Now open the header file, will reflect all the on-chip resources of 80C51 as shown below: ------------------------------------------------ 51.H er file for generic 80C51 and 80C31 microcontroller. right c© 1988–2002 Keil Elektronik GmbH and Keil Software, Inc. ghts reserved. -----------------------------------------------∗/ ef REG51 H sbit EX1 = 0xAA; ne REG51 H sbit ET0 = 0xA9; /∗ BIT Register ∗/ sbit EX0 = 0xA8; YTE Register ∗/ /∗ PSW ∗/ 0 = 0x80; sbit CY = 0xD7; /∗ IP ∗/ 1 = 0x90; sbit AC = 0xD6; sbit PS = 0xBC; SW = 0xD0; sbit RS0 = 0xD3; sbit PT0 = 0xB9; CC = 0xE0; sbit OV = 0xD2; sbit PX0 = 0xB8; = 0xF0; sbit P = 0xD0; P = 0x81; /∗ P3 ∗/ PL = 0x82; /∗ TCON ∗/ sbit RD = 0xB7; PH = 0x83; sbit TF1 = 0x8F; sbit WR = 0xB6; CON = 0x87; sbit TR1 = 0x8E; sbit T1 = 0xB5; CON = 0x88; sbit TF0 = 0x8D; sbit T0 = 0xB4; MOD = 0x89; sbit TR0 = 0x8C; sbit INT1 = 0xB3; L0 = 0x8A; sbit IE1 = 0x8B; sbit INT0 = 0xB2; L1 = 0x8B; sbit IT1 = 0x8A; sbit TXD = 0xB1; H0 = 0x8C; sbit IE0 = 0x89; sbit RXD = 0xB0; H1 = 0x8D; sbit IT0 = 0x88; = 0xA8; /∗ SCON ∗/ = 0xB8; /∗ IE ∗/ sbit SM0 = 0x9F; CON = 0x98; sbit EA = 0xAF; sbit SM1 = 0x9E; BUF = 0x99; sbit ES = 0xAC; sbit SM2 = 0x9D; sbit ET1 = 0xAB; sbit REN = 0x9C; TB8 = 0x9B; sbit TI = 0x99; RB8 = 0x9A; sbit RI = 0x98; #endif Figure 3.1 On-chip resources in the window rces pertaining to this device as shown below. ------------------------------------------------ 52.H er file for generic 80C52 and 80C32 microcontroller. right c© 1988–2002 Keil Elektronik GmbH and Keil Software, Inc. ghts reserved. -----------------------------------------------∗/ ef REG52 H sfr IP = 0xB8; ne REG52 H sfr SCON = 0x98; sfr SBUF = 0x99; YTE Registers ∗/ 0 = 0x80; /∗ 8052 Extensions ∗/ /∗ TCON ∗/ 1 = 0x90; sfr T2CON = 0xC8; sbit TF1 = TCON∧7; 2 = 0xA0; sfr RCAP2L = 0xCA; sbit TR1 = TCON∧6; 3 = 0xB0; sfr RCAP2H = 0xCB; sbit TF0 = TCON∧5; SW = 0xD0; sfr TL2 = 0xCC; sbit TR0 = TCON∧4; CC = 0xE0; sfr TH2 = 0xCD; sbit IE1 = TCON∧3; = 0xF0; sbit IT1 = TCON∧2; P = 0x81; sbit IE0 = TCON∧1; PL = 0x82; /∗ BIT Registers ∗/ sbit IT0 = TCON∧0; PH = 0x83; /∗ PSW ∗/ CON = 0x87; sbit CY = PSW∧7; /∗ IE ∗/ CON = 0x88; sbit AC = PSW∧6; sbit EA = IE∧7; MOD = 0x89; sbit F0 = PSW∧5; sbit ET2 = IE∧5; L0 = 0x8A; sbit RS1 = PSW∧4; //8052 only L1 = 0x8B; sbit RS0 = PSW∧3; sbit ES = IE∧4; H0 = 0x8C; sbit OV = PSW∧2; sbit ET1 = IE∧3; H1 = 0x8D; sbit P = PSW∧0; sbit EX1 = IE∧2; = 0xA8; //8052 only sbit ET0 = IE∧1; EX0 = IE∧0; sbit RCLK = T2CON∧5; ∗/ sbit TCLK = PT2 = IP∧5; T2CON∧4; X1 = IP∧2; sbit TR2 = T0 = IP∧1; T2CON∧2; X0 = IP∧0; sbit C T2 = T2CON∧1; ∗/ sbit CP RL2 = RD = P3∧7; T2CON∧0; WR = P3∧6; T1 = P3∧5; #endif T0 = P3∧4; NT1 = P3∧3; NT0 = P3∧2; TXD = P3∧1; RXD = P3∧0; ON ∗/ M0 = SCON∧7; M1 = SCON∧6; M2 = SCON∧5; REN = SCON∧4; TB8 = SCON∧3; RB8 = SCON∧2; TI = SCON∧1; RI = SCON∧0; ∗/ T2EX = P1∧1; 52 only T2 = P1∧0; 52 only CON ∗/ TF2 = T2CON∧7; XF2 = ON∧6; te the bold letters which are exclusively added for the 80C52 only. tartup procedures for the 8051 are contained in startup.a51. This included in your project and will be assembled together with ompiled output of your C program. For custom applications, this up file might need modification, because the stack or stack space, are predefined as per the memory model. Basic C Program Structure ting below shows a basic structure for a C program. ----------------------------------- sic blank C program that does nothing cludes ----------------------------------- lude <reg51.h> // SFR declarations main (void) { e(1); { body of the loop // Infinite loop } } // match the braces te: Similar to conventional C, all the variables must be declared at art of a code block, you cannot declare variables in the midst of rogram statements. Differences from ANSI C ere are marginal differences of Cx51 compiler from the ANSI mpiler. These differences are twofold, viz. compiler related and y related. The details are given in the help menu of the Keil Frequently used things are given below for ready reference of the ammers. able Types e Keil C compiler supports most ANSI C variable types and in on has several of its own. C compiler as the basic 8051 core is not efficient for the same. The supported are as follows: Type Bits Bytes Range Char 8 1 −128 to +127 Unsigned char 8 1 0 to 255 Enum 16 2 −32, 768 to +32, 767 Short 16 2 −32, 768 to +32, 767 Unsigned short 16 2 0 to 65, 535 Int 16 2 −32, 768 to +32, 767 Unsigned int 16 2 0 to 65, 535 Long 32 4 −2, 147, 483, 648 to 2, 147, 483, 647 Unsigned long 32 4 0 to 4, 294, 697, 295 Types e bit and Boolean capabilities of MCS-51 family are well explored e Keil C Compiler by adding several new types. Some of them are ows: Type Bits Bytes Range Bit 1 0 0 to 1 Sbit 1 0 0 to 1 Sfr 8 1 0 to 255 Sf16 16 2 0 to 65, 535 these, only the bit type works as a standard variable. The other have special behavior that a programmer must be aware of. The pe gets allocated to the 8051’s bit-addressable on-chip RAM. Note you cannot declare a bit pointer or an array of bits. The special on registers are declared as a sfr data type in Keil C. If you give ddress of the SFR as 0x80h then it gets allocated to port 0 of Extensions of the 8051 often have the low byte of a 16 bit register ding the high byte. Therefore the timer 0 for instance should be ed as a 16-bit special function register, sfr16, giving the address of w byte: TMR0RL = 0x8A; // Timer0 reload value TMR0 = 0x8B; // Timer0 lower ble extensions. Following table summarizes the same. Assembly age mnemonics are used to indicate the subsequent meaning of ariable extension used. ension Memory Type Related ASM a Directly-addressable data mem- ory (data memory addresses 0x00-0x7F) MOV A, 056h a Indirectly-addressable data memory MOV R0, #09Ah (data memory addresses 0x00-0xFF) MOV A, R0 a External data memory MOVX @DPTR e Program memory MOVC @A+DPTR case the memory type extension is not specified, the compiler will e which memory type to use automatically, based on the memory l (SMALL, COMPACT, or LARGE, as specified in the project rties in Keil). pter 4 ploring the Capabilities of On-Chip ources Programming for I/O Ports, errupts and Timer/Counter Importance of Ports rts are the means through which the microcontroller communi- with the outside world. They are the most common I/O devices. teresting point to note is that the number of I/O pins or ports ecided by the packaging style of the microcontroller. A compari- various packages is given below: A new trend in 8-bit controller n is to place the chip inside a 20-, 16-, or even 8-pin PDIP or SOP ge, allowing for very small and cheap embedded systems to be ructed [29]. tunately most of the derivatives of the 8051 are generally offered pin DIP or 52-pin PLCC packages and there is not much varia- n terms of package pinouts. The obvious advantage of the upward atibility maintained into the different versions of the 8051, is irect replacement of the latest advanced 8051 from Intel to its predecessor without even changing the printed circuit board. “drop-in” replaceability is rarely true of other microcontroller ectures [30]. ying with the Ports gram 4.1: Simulated Port Testing Using Keil e program illustrates simple port programming in a simulated mode the Keil compiler. A sample data is sent to the port and the output erved in the simulator window. You may as well connect LEDs to ve the output. 37 rab et al. (eds.), Exploring C for Microcontrollers, 37–67. Springer. ge Number of pins Features Applications (plastic n-line e) 8–64 Through hole type devices, dense style package, pins/area ratio of PDIP not very efficient Prototype or hobbyist type applications, smaller 8-bit microcontrollers (plastic arrier) 20 up to 80+ Through hole type devices Small, low-pincount microcontrollers (small ted ) or (small e) 8–64 pins Pins are spaced much closer together, package designed to be soldered directly to the top of a board quad flat e) 8–220+ pins Sophisticated soldering workstation required to deal with the pins closely spaced 16- to 32-bit microcontrollers to 64-bit superscalar microprocessors gram Source Code ********************************************** ude<reg51.h> /∗ special function register declarations for the intended 8051 derivative. The header file contains the definitions of special function registers (SFRs) and other functions. ∗/ main(void) // Start of the Main function. P1=0x44; /∗Send 44H to port P1∗/ P2=0x55; /∗Send 55H to port P2∗/ // End of the main function. ********************************************** e screenshot of simulation window shown in Figure 4.1 the data ry to port 1 and 2. Figure 4.1 Screenshot of simulation window showing the ports gram 4.2: Sending Out Different Contents to Port 1 ferent data bytes are sent to port 1 after delay. The results can be ed in the simulation window, which shows the changing of data on ort 1 lines. gram Source Code ****************************************** ude <REG52.H> delay(void); delay(void) /∗ invoking delay function ∗/ =0;i<30000;i++); =0;i<30000;i++); while(1) { P1 = 0x01; // Out 01 on the port 1. delay(); // Delay function. P1= 0x02; // Out 02 on port1. delay(); P1=0x04; delay(); P1=0x08; delay(); P1=0x10; delay(); P1=0x20; delay(); P1=0x40; delay(); P1=0x80; delay(); P1=0x40; delay(); P1=0x20; delay(); P1=0x10; delay(); P1=0x08; delay(); P1=0x04; delay(); P1=0x02; delay(); P1=0x01; delay(); } // termination of the while loop. // termination of the main function. ****************************************** 1 contents are complemented and sent to the port 1. The square can be observed on port 1 by using CRO. gram Source Code ******************************************* ude<reg51.h> delay(int); delay(int k) ; =0;j<k+1;j++){ =0;i<100;i++); main(void) // Start of the main function. int N1=0; // Defining the integer value for the er. while(1) // Infinite loop { P1=N1 ; /∗ Assign N1 to port P1∗/ N1 =∼N1; /∗Complement N1∗/ delay(10); /∗ Delay which defines the on and off time for the Square wave. ∗/ P1 = N1; /∗Send it to port P1∗/ delay (10); } // End of while loop. // End of main. ******************************************* is program illustrates assigning values to the character and then ng it to the port. Here the characters a, b, c are assigned with the numbers and these values are sent to ports. gram Source Code ********************************************** ude<REG51.H> main(void) char a,b,c; // Define the characters a, b and c. while(1) { a=0x01; /∗ Assign 01H to ‘a’ ∗/ b=0x02; /∗ Assign 02H to ‘b’ ∗/ c=0x03; /∗ Assign 03H to ‘c’ ∗/ P0=a; /∗ Send value assigned to ‘a’ to port 0∗/ P1=b; /∗ Send value assigned to ‘b’ to port 1∗/ P2=c; /∗ Send value assigned to ‘c’ to port 2∗/ } ********************************************** gram 4.5: Configuring the Ports as Input default all the ports act as output port. They can be configures put by writing FFH to them. The programmer need not bother the actual SFR address. Thanks to the header file included at op. e actual input operation is simulated by assigning values to the bles. The actual DIP switch interfaced as input device is covered er in the text. ogram below illustrates the simplest way to define the ports as an port and how to read the input from the ports and the result is ved in the simulation window. ude<REG52.H> main(void) char N1,N2,N3; // Defining the characters. P0=0xFF; // set P0 as input P1=0xFF; // set P1 as input while(1) { N1=P0; /∗Input value of P0 in N1∗/ N2=P1 ;/∗Input value of P1 in N2∗/ N3=N1+N2; // Addition of the two inputs P2=N3; /∗Send value of N3 to port 2∗/ } ****************************************************** gram 4.6: Software Delay Loops Combined h I/O Ports e program demonstrates generation of software delay using two operating on a single count. An integer x is declared and assigned nt equal to 10,000. “While(1)” loop keeps the program in continues The other two loops are conditional with the first loop executes “while(x > 1)” is valid, i.e., when x is greater than 1. The other executes when x is less than 10,000. Note the usage of decrement and increment (++) operators. Both these loops are embedded in ain loop. observe the output of this connect the port 1 to LEDs. The output so be verified in the simulator window. gram Source Code ******************************************************** ude <reg51.h> main (void) (1) while(x > 1) /∗ 10000 count delay ∗/ { P1 = 0x0f; /∗ set leds on PORT1 to 00001111 ∗/ x- -; /∗ decrement x ∗/ } // end of first loop while(x < 10000) /∗ 10000 count delay ∗/ { P1 = 0xf0; /∗ set leds on PORT1 to 11110000 ∗/ x++; /∗ increment x ∗/ } // end of second loop. // End of open loop. End of main. ******************************************************** gram 4.7: Alternate Method of Software Delay eration with Port Programming is program illustrates the use of “FOR” construct for delay gener- which toggles only one port pin (P1.1). te the use of ! operator for complementing the variable. gram Source Code ******************************************************** ude<reg52.h> in = P1∧0 ; //Pin declaration vin = port 1 pin 0 main(void) int i; vin = 1; //Make port pin P1.0 high while(1) { for(i=0;i<=3000;i++); // Delay generation delay } ******************************************************** Figure 4.2 LED interface to microcontroller port pin gram 4.8: Shifting the Port Contents to Left is program shifts the contents of port 0 to left. The result may be n the simulation window by opening the menu option for periph- The port bits goes on changing one by one. gram Source Code ******************************************************** ude <REG52.H> main(void) int i; char N1; while(1) { N1=0x01; while(N1!=0x00) //Continue the loop till N1 not equal to 00H //When N1=00H program exits the loop { port 0 N1=N1<<1; //Left shift N1 by one bit position } } /∗ try right shift by using right shift operator ‘>>’ ∗/ ******************************************************** Simple Ideas for Port Expansion e users are worried when the number of I/O port lines poses a bot- k for applications especially in the areas of robotics and industrial ss control. In these types of application domains the user may either another microcontroller with more I/O pins or interface chips like 255 to the existing ports. However, there are many simple methods pand the port. Few of them tried by embedded system developers ven herewith the source URL, so that the user may adopt them eir applications. 2 Wire Input/Output for 8051 type CPUs [31]. The application note explains the use I2C 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. LED Interfacing e simplest applications such as port testing or indication may only re on/off-type LEDs for displaying status information. For such ap- ions, LEDs can be controlled directly by a general-purpose I/O pin le of sourcing or sinking the necessary current required for lighting ED, typically between 2 mA and 10 mA. LEDs have exponential ge-current characteristics, that means around the operating point is rapid increase in current for little increase in voltage. Therefore y a constant current source is desirable to drive the LEDs. How- the same can be simulated by using a series resistor connected to ort pin so that the voltage across the LED will be fairly constant. Figure 4.3 Interfacing diagram for a LED nerally a common anode connection is chosen in a digital environ- because pull-down is much easy as compared to push-up. If an nal power supply is used, then the corresponding brightness will be better as compared to driving logic 1 through the microcontroller pins. From a programmer’s point of view this means by writing 0’ the LED will glow (see Figure 4.3). ree things are required for working with the LEDs: the driving ge, the current to be passed, and the forward voltage drop across ED. For a blue LED with 12 V supply, in order to glow a single a current of the order of 20 mA is required to be passed. With the rd voltage drop of 3.4 V, the value of the resistor can be calculated simple Ohm’s law as follows: R = VS-VL/I e VS = the supply voltage VL = voltage across the LED I = Current through the LED. tput. The choice of the series resistor and its wattage is covered in standard books. Relevance of LEDs in Today’s Lightening Industry eet lighting is fast emerging as a potentially strong market for , since these devices have reached a level of output and efficiency to them viable replacements for incumbent lighting technologies. The ntages of LED-based street lights are reduced energy consumption, maintenance, and better light quality [33]. Novel interfacing tech- s based on microcontroller are emerging which ranges from simple ost current limiting resistors to dynamic constant current utilizing Ms and analog-to-digital converters. With HB-LED lighting requir- he use of low-voltage electronic control, low-cost microcontrollers seful in bringing additional compelling features to household light- Microcontrollers are making it easier for lighting designers to in- rate a reliable connectivity interface such as DALI and DMX512 will provide the backbone for adding remote user controls [34]. The mentioned interfaces are based on packet-based system to deliver ata to the LED matrix. The technique has been covered in depth s chapter. Different Programs for LED Interfacing gram 4.9: Blinking LED is program illustrates simple LED blinking at a constant interval. mple technique of complementing a bit is used with changing soft- delay. The hardware shown Section 4.3 is used. gram Source Code ************************************************** ude <REG52.H> /∗ special function register declarations for the intended 8051 derivative ∗/ delay(void); /∗declaring a delay routine for blinking al∗/ delay(void) main(void) // invoking main function. ybit; // define the bit as a mybit. = 1; // assign the mybit a logic high (1) // indefinite loop = !mybit; // complement the bit mybit; // send the complemented bit to port 1 (); // invoke the delay routine // termination of the while loop // termination of the main function ************************************************** gram 4.10: Scrolling LED is program illustrates the interfacing of LED with scrolling pattern. display appears as if the LED is shifting. The LED connected to ort 0 glows one by one. A software delay is used to define scrolling al. gram Source Code ************************************************** ude <REG52.H> main(void) int i; // define the integer number char N1; //define the character to assign the hex number while(1) { N1=0x01; while(N1!=0x00) // routine for scrolling interval { for(i=1;i<10000;i++); N1=N1>>1; //shift right by one } } ************************************************** te: Similarly one can write the program for the Shifting the LED reverse order. gram 4.11: Exploring Bit Capabilities he Microcontroller is program makes use of the microcontroller’s bit programming ility. Here the single port pin is used as an output. The program es the single port pin to give a continuous on/off pattern on pin Input from P1.0 is simulated. gram Source Code **************************************************** ude<reg52.h> an= P1∧0; /∗ Pin declaration vinod = port 1 pin 0∗/ ew = P1∧1; /∗ Pin declaration new = port 1 pin 1∗/ main(void) int vinod; // Define the int vinod vinod = 0x00; while(1) /∗ Infinite loop (i.e.,countinuos loop)∗/ { van = vinod; /∗ Simulating input from port pin P1.0 and assigning the same to character van ∗/ new = vinod; /∗ send output to port1 pin1 ∗/ vinod=!vinod; //compliment vinod } // end of loop } // End of main **************************************************** sed on the programs given above many advanced projects are ble. Given below is the list of project ideas, which can be explored ittle efforts by modifying the LED interfacing circuit. 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. 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. 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 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. 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 20mA 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. 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. DIP Switch Interfacing: Getting Input to Your Embedded System al in-line package (DIP) switches are electronic packages that con- f a series of tiny switches. DIP switches are used to configure com- s and peripherals such as circuit boards and modems. They are useful for testing purpose. On our kit an eight input DIP switch vided with all its inputs available through the male connector on oard. Any port can be connected to this DIP switch by simply cting the associated male connectors. This scheme is very useful mulate a digital input to the microcontroller. Figure 4.4 DIP switch interfacing to microcontroller gram 4.12: DIP Switch Interfacing ogram for getting the DIP switch status and outputting the same ED. DIP switch status is read through port 1. LEDs are connected rt 0 to display the status read. gram Source Code ************************************************ ude <REG52.H> main(void) N1; //Define the character for assignment of the umber. P1 = 0xFF; // Define the port P1 as a input port. while(1) { N1=P1; // Assign the value read from the port 1 to N1. P0=N1; /∗ display the status of the DIP switch on the LEDs connected to port 0. ∗/ } // End of “while” // End of “main” ************************************************ ucts like cell phone, data loggers and process control instruments. e 4.5 shows LCD controller Hitachi 44780 that provides a relatively e interface between a processor and an LCD. Since the LCD inter- g is used in almost all our applications, a datasheet and other details ven in annexure I. Three output pins, viz., P2.0, P2.1 and P2.2 are for controlling the LCD. The data is passed on to the LCD using 1. e most important thing in LCD interfacing is to apply a minimum 0 ns wide high to low pulse to the enable pin of the LCD. This is to activate the latch of Hitachi 44780 to grab the data on the port t that instance. Figure 4.5 LCD interfacing to 8051 microcontroller is program displays the string “We Thank Springer Publishers Authors” on the LCD. The comments are self-explanatory. gram Source Code **************************************************** ude <REG52.H> /∗ special function register declarations ∗/ /∗ for the intended 8051 derivative ∗/ RS = P2∧0; // Control signal RESET of the LCD connected to pin P2.0 RW = P2∧1; // Write (RW) Signal pin connected to pin P2.1 N = P2∧2; // Enable (EN) LCD control signal connected to pin P2.2 delay(void); // Delay function NIT(void); // Function for the commands to Initialization of the LCD ENABLE(void); // Function for the commands to enable the LCD LINE(int); /∗ Function for the commands to choose the line for displaying the characters on the LCD ∗/ LINE(int i) // start of LINE function if (i==1) { RS=0; // first make the reset signal low RW=0; // make RW low to give commands to the LCD P1=0x80; // force cursor to beginning of the first line ENABLE(); // enable the LCD RS=1; } else { RS=0; RW=0; P1=0xC0; // force cursor to beginning of the second line ENABLE(); RS=1; } =0;j<10;j++) =0;i<100;i++); ENABLE(void) // Invoking the enable function =1; // Give high to low pulse to Enable the LCD. (); 0; (); NIT(void) // Initialization of the LCD by giving the proper commands. RS=0; RW=0; EN=0; P1 = 0x38; // 2 lines and 5∗7 matrix LCD. ENABLE(); ENABLE(); ENABLE(); ENABLE(); P1 = 0x06; //Shift cursor to left ENABLE(); P1 = 0x0E; // Display ON, Cursor Blinking ENABLE(); P1 = 0x01; // Clear display Screen. ENABLE(); main (void) code dis[] = “We Thank Springer Publishers”; code dis2[] = “From Authors”; // Array of characters to be display. (1) =1;x<3;x++) ); (1); // Display on the line 1 of the LCD. =1) dis; // point the character address from the array “dis” where it is stored. dis2; // Point the Character address from the “dis2” where it is stored/ =0;j>8;j++){ P1= ∗p++; // Increment the pointer by 1. ENABLE(); } (2); // Display the second array on the second line on the LCD. **************************************************** Interrupts in Microcontrollers errupts are of immense importance in any microcontroller-based m. A peripheral such as timer/counter, A to D converter, or even a ry or a keyboard can interrupt the microcontroller from its ongoing ntial execution to let it know that it requires attention. This may be o several reasons such as timer overflowing, ADC returning data, or gnal on an input pin changing. Generally, many standard references are the polling technique with the interrupt and concludes that the upt is a superior technique. However, in microcontroller paradigm, developer intends to use the polling technique, then he will have to But the interrupt offers a flexible and time-efficient response to xternal events with the least software overhead. errupts in 8051 microcontroller are as follows: Timer 0 Overflow Timer 1 Overflow Reception/Transmission of Serial Character External Event 0 External Event 1 1 Writing ISRs in C gram 4.14: is simple program illustrates the initialization sequence for the , serial I/O and interrupt. A function called “serial int” is set as the er for interrupt 4, which is the serial port interrupt. A character sent to the serial buffer. Observe this in the simulation window of DE. gram Source Code **************************************************** rial Port Interrupt ude <reg52.h> ude <stdio.h> void main (void) { int i; TMOD = (TMOD & 0xF0) | 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 bit while (1) { SBUF = ‘V’; //Send V continuously on //Serial Port for(i=0;i<=10;i++); /∗ Delay to avoid trans- mission overlapping ∗/ } } rial Port Interrupt Service Routine. void timer0 ISR (void) interrupt 4 { TI = 0; //Clear transmission interrupt flag } **************************************************** gram 4.15: is program is modification of the Program 4.14. Unlike the inter- technique used in Program 4.14, here the interrupt flag is polled nuously. Observe the transmission of ‘v’ in simulator window. gram Source Code **************************************************** rial port Interrupt Programming ude<REG52.H> main() TMOD=0x20; // Timer 1 Mode 2 TH1=0XFD; // Baud rate = 9600 for 11.0592 SCON=0X50; //Serial Communication mode 1 TR1 = 1; // Start Timer 1 TI = 0; // Clear Transmit Interrupt flag while(1) { SBUF = ‘v’; // Send ‘v’ continuously on Serial port while(!TI); // Check TI flag till it is zero TI = 0; // Clear Transmit Interrupt flag } **************************************************** gram 4.16: Implementation of Minutes Counter is program implements a seconds counter on the serial seven- ent LED. Timer 0 is used for the generation of delay of a minute. elapsing of the delay routine the count is incremented and dis- d on the serial seven-segment LED. The 4 seven-segment display is y connected. Pins P3.7 is used for clock generation and the data nsferred serially over the pin P3.6. gram Source Code **************************************************** ude<REG52.H> display(char a); clear(void); NIT (void); delay(void); ned int count, milliseconds; // Unsigned Integers for the count. at=P3∧6; // Set the pin to Sending the data bits over the pin P3.6 lk=P3∧7; // Set the pin to send clk 0x90}; delay(void) // Invoking the Delay routine d; =0;c<2;c++) d=0;d<2000;d++); NIT (void) // Invoking the function to start the timer D=0X01; =0; /∗ Timer 0 overflow flag reset first, Start the timer and set the interrupt when timer overflows ∗/ =0; 1=50000; 1=∼delay1; // Complement the delay count delay1%256; // Count loaded in the Timer 0 lower byte. =delay1/256; // Load the higher byte of timer 0 =1; // Run the timer 0 =1; 1; // Global interrupt bit x00; lear(void) /∗ Invoking the function to clear the display ∗/ 1; =0;j<32;j++) ; // Sending the pulse to clear the display ;clk=0; display(char a) // Display the numbers on the seven-segment LEDs ned char mask; =0x80; // Mask the higher digit mask) 1; 0; ; ;clk=0; =mask>>1; /∗ If the unit digit goes overflow then switch the upper digit. ∗/ main(void) // Invoking the main function ned char m,n; ); =0; milliseconds=0; (); // Initializing the timer r (); n=count%10; m= ( (count/10) % 10); play(s[m]); // Display the count at higher digit position play(s[n]); // Display the count on the lower digit position (); (count < 60); =0; le (1); ) interrupt 1 // Function for the interrupt routine when timer overflows =0; TF0=0; // Reset the timer and the timer flag 1=50000; 1=∼delay1; =delay1%256; =delay1/256; ++; // Increment the count econds=0; =1; // Run the timer 0 **************************************************** 2 A Word about Interrupt Latency errupt latency is the time between the generation of an interrupt evice and the servicing of the device which generated the interrupt. her words it is the time taken to service the interrupt or the longest between when the interrupt occurs and when the microcontroller nds the current processing context. errupt latency is an important issue in microcontroller-based sys- esign for several reasons. Microcontroller-based system with a sin- terrupt will execute correctly (as per the intended logic of the oper) provided ISR execution time is smaller than the frequency interrupt. One of the most important issues in microcontroller- embedded systems is the power consumption, since the system at remote installation with long battery life. From the low power mption point of view, the crystal frequency should be at the low- nd of the permissible limit. This value is ultimately decided by terrupt latency (generally the standard values should be adopted e prescribed baud rates in serial communication). Improving the upt latency results into lowering down the throughput and increas- e processor utilization. On the other hand, reducing the processor ation may increase interrupt latency but may decrease the overall ghput. gram 4.17: Estimating Interrupt Latency gram Source Code **************************************************** ude <REG52.H> /∗ special function register declarations ∗/ /∗ for the intended 8051 derivative ∗/ RS = P2∧0; RW = P2∧1; nterrupt1 = P3∧3; // External interrupt N =P2∧3; delay(int); NIT(void); ENABLE(void); LINE(int); NTIME(int); LINE(int i) // Enabling the Line function if (i==1) { RS=0; RW=0; P1=0x80; ENABLE(); RS=1; } else { RS=0; RW=0; P1=0xC0; ENABLE(); RS=1; } delay() ; =0;j<10;j++){ =0;i<100;i++); ENABLE(void) // Invoking the Enable function for the LCD. 1; (); NIT(void) // Initialization of the LCD by giving the proper commands RS=0; RW=0; EN=0; P1 = 0x38; // 2 lines and 5∗7 matrix LCD ENABLE(); ENABLE(); ENABLE(); ENABLE(); P1 = 0x06; // Shift cursor to left ENABLE(); P1 = 0x0E; // Display ON, Cursor Blinking ENABLE(); P1 = 0x01; // Clear display Screen ENABLE(); NTIME() // Invoking the ONTIME function D=0x01; // Intialize as 16 bit timer(mode 1)(Timer 1) 0x00; =0x00; =1; // start the timer ; /∗input to 8052 from 555 osc∗/ (IN); (!IN); (IN); =0; // stop the timer n((TH0∗256)+TL0); // return the ISR Execution count main (void){ tency, unit, tens, hundred, thousand, code dis2[] =“Interupt Latency=”; ∗p; ; (1) D=0x01; // Initialize the timer to count the total program execution time =0x00; =0x00; =1; // Start the timer 1 errupt1==1) NTIME(); = (i%10); = (i/10)%10; red = (i/100)%10; and = (i/1000)%10; ou = (i/10000)%10; = unit + 0x30; // Sending the ASCII data to the LCD = tens + 0x30; red = hundred + 0x30; and= thousand + 0x30; ou = tenthou + 0x30; (); (1); dis; =0;j<8;j++){ P1= ∗p++; ENABLE(); } (2); enthou; BLE(); housand; BLE(); undred; BLE(); nit; BLE(); dis2; =0;j<8;j++){ P1= ∗p++; // Pointer to point the data from the array ENABLE(); // Enabling the LCD } (2); // Display the content on the second line of the LCD =0; // stop the timer 2 y=(((TH1-TH0)∗256)-(TL1-TL0)); //Timer 0 count is subtra- cted from timer1 = (latency%10); = (latency/10)%10; ed1 = (latency/100)%10; and1 = (latency/1000)%10; ou1 = (latency/10000)%10; = unit1 + 0x30; = tens1 + 0x30; ed1 = hundred1 + 0x30; and1= thousand1 + 0x30; ou1 = tenthou1 + 0x30; (2); enthou; // display the latency BLE(); housand; BLE(); undred; BLE(); ens; BLE(); nit; BLE(); **************************************************** pter 5 perterminal-Based Control Hyperterminal perTerminal is a terminal emulator program that runs in MS ows. It offers a text-based command prompt interface on a e device. The remote device is a serial device, and it could be ter, connected directly to the PC’s serial port OR a network e. HyperTerminal is generally used for the local serial interface for unications or the network. In the case of the network, HyperTer- is simply using the telnet protocol. In order to communicate with evice, the HyperTerminal must be configured on the right COM (either COM1 or COM2) and at appropriate baud rate (most of me 9600 for applications written here). ving designed to emulate various types of text terminal configurable ke a over a serial port the serial parameters to be selected are: Baud rate Parity (odd, even, none) Stop bits Flow control Packet-based Control Scheme e beauty of the programs covered in this section is that they present sight with regard to the new protocol development. The remote i.e., microcontroller board connected to COM1, has various com- blocks which will be invoked based on the parameters passed from yperTerminal. The command blocks are packed and a particu- acket corresponding to the desired control sequence that is made as soon as the associated command parameter is received from the rTerminal. 69 rab et al. (eds.), Exploring C for Microcontrollers, 69–83. Springer. election of proper baud rate. A standard serial interfacing for PC, 2C, requires negative logic, i.e., logic ‘1’ is −3V to −12 V and logic +3 V to +12 V. In order to convert a TTL logic, say, TxD and pins of the microcontroller chips, a converter chip is required. A 232 chip is a very popular chip used in the circuit boards for all the cations covered in this chapter. It provides 2-channel RS232C port equires external 10uF capacitors. The polarity of the capacitor is al which the user must note. Another possibility in lieu of MAX232 275, which does not require an external capacitor. Mechanism and Lots of Possibilities e mechanism of packet-based interface works as follows. The num- control possibilities are listed in case of each control module and orized in terms of packets. For instance, in case of the LED inter- board, various display sequences are defined as packets. In case of er motor-based interface the packet definitions include the clock- anticlockwise rotations in the first instance and step size as the dary instance, both the things defined together. As per the firing commands from the HyperTerminal the firmware residing in the controller flash will invoke the appropriate control action. e following simple steps will help you to configure the rTerminal. Open the HyperTerminal, by clicking Start>Programs>Accessories>Communications>HyperTerminal. 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. Select the serial port where the device is connected to the PC (COM1 in our case). Click OK. Enter the following configuration for the connection: Bits per second 9600 Data bits 8 Parity None Stop bit 1 Flow control None Click OK.