Programming 16-Bit PIC Microcontrollers in C. Learning to Fly the PIC 24

386 Pages·2011·6.74 MB·English

by  Lucio Di Jasio (Auth.)

Programming 16-Bit
PIC Microcontrollers in C
Programming 16-Bit
PIC Microcontrollers in C
Learning to Fly the PIC 24
Second edition
Lucio Di Jasio
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This book is dedicated—
To Sara and Luca
Preface
Writing this book turned out to be much more work than I had expected and believe me,
I was already expecting a lot. This project would have never been possible if I did not have
110% support and understanding from my wife. Special thanks also go to Steve Bowling,
a friend, a pilot and an expert of Microchip 16-bit architecture, for reviewing the technical
content of this book and providing many helpful suggestions for the demonstration projects
and hardware experiments. Many thanks go to Eric Lawson for constantly encouraging me
to write and for all the time he spent to fix my eternally long running sentences and my bad
use of punctuation. I owe big thanks also to Thang Nguyen, who was first to launch the
idea of the book; Joe Drzewiecky and Vince Sheard for patiently listening to my frequent
laments, always working hard on making MPLAB a better tool; Calum Wilkie and Guy
McCarthy for addressing quickly all my questions and offering so much help and insight into
the inner workings of the MPLAB C compiler and libraries. Among the technical reviewers
of the second edition, I would like to add special thanks to Stewart Cording, Tom Mignone,
and Wayne Duquaine who helped me adapt the code to the many new families of PIC24
devices. But I would like to extend my gratitude to all my friends, ex-colleagues at Microchip
Technology and the many embedded control engineers I have been honored to work with
over the years. You have so profoundly influenced my work and shaped my experience in the
fantastic world of embedded control.
xv
Introduction to the Second Edition
In the six years since I completed the first manuscript of this book, there has been a
tremendous evolution of the PIC24 architecture and all the supporting set of tools and
documentation. What seemed like a promising, if only embryonic, new product line has
become one of the main driving forces in Microchip Technology’s portfolio. The number of
different models available has long passed the 100 mark. It's been growing up toward larger
and larger memory sizes and more complex devices as well as down to smaller, simpler
devices in tiny packages and with minuscule power consumption figures where, once upon a
time, it used to be the undisputed sole domain of the smallest of the 8-bit PIC® architectures.
Back then, when looking for evaluation boards, there was only one choice: the Explorer16 and
that is what I had to use for the first edition of this book. Today the choice has been expanded
to hundreds of new options offered by numerous and creative third parties worldwide.
Interestingly, after much consideration, my final choice for this second edition has been to
remain focused mainly on the Explorer16 demonstration board although the reader will be able
to reproduces most/all examples and exercises on many other equivalent tools. This choice
can be considered a testament to the success of the board in itself and the huge portfolio of
expansion boards – known today as the PICTail Plus boards – that complete it. The Explorer16
today can be used to evaluate all 16-bit and 32-bit devices (dsPIC® digital signal controllers
included) available in packages of 64 pin or higher, with clock frequencies that have reached
80 MHz at the time of this writing and will certainly pass that mark in the coming years.
The same could be said for the programming and debugging tools. When once upon a time
the ICD2 used to be the one and only choice, today there is a range of tools, from the simple
and inexpensive PICKit3 to the fast and sophisticated REAL ICE, that can cover with agility
the entire portfolio of 600 models of 8-bit, 16-bit and 32-bit microcontrollers offered by
Microchip.
So for this second edition my tool of choice has shifted (only slightly) to the generic PICKit3,
for its cost, or the ICD3, for its speed, preferring them to more PIC24-specific tools of even
lower cost (PIC24F Starter kit, PIC24H Stick…) considering that the work done in this book
will represent only a starting point and the PICKit3 and ICD3 in circuit debuggers will have
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xviii Introduction to the Second Edition
the ability to continue to support you well beyond these 15 chapters and into the real world of
embedded control.
As per the MPLAB Integrated Development Environment, the evolution in these years has
been relentless but incremental for the most part. In the last few months, I had the opportunity
to test drive the new MPLAB X platform, an almost complete redesign of the tool around an
open source platform known as NetBeans. MPLAB X offers tons of new features but also
runs on a wider range of operating systems (including MAC OS X, and Linux at last). Most
importantly it brings the promise of a greater stability and robustness.
Every chapter in this book has been revised to accommodate for the new MPLAB X interface.
In most cases, this has resulted in a simplification of what used to be long sequences of
operations, previously detailed in extensive checklists, and now reduced to single mouse
clicks.
Finally let me add a word about the MPLAB C compiler, the PIC24F peripheral libraries
and the Microchip Application Library. Here the evolution has been steady but nothing short
of spectacular. The work on the compiler (now based on the open source GNU GCC v4
project) has been relentless and the real proof of quality of the results today can be quickly
summarized in two bullets:
l None of the examples in this book required a single line of assembly code! This is in
stark contrast to the first edition, when in several chapters I had to augment the examples
with numerous and, at times, cryptic assembly code workarounds.
l Both performance and code size figures had to be corrected in most/all chapters as the
compiler produced much tighter code (up to 30% smaller) and faster code (removing the
need for extensive hand optimizations) while utilizing only optimization levels 0 and 1
available on all the evaluation (as in free) copies of the compiler.
The PIC24 peripheral libraries have remained an interesting but mixed bag from my point
of view. So I have been picking and choosing, very selectively, chapter by chapter when,
why and what to take from them. The Microchip Application Libraries (MAL), a large
collection of modules that used to be offered as separate application notes (USB, Ethernet,
Graphic displays…) deserve a separate mention. Unfortunately the size of the library and the
complexity of the subjects covered made it impossible for me to add in this book more than
a few hints here and there, and links at the end of related chapters. Each library in the MAL
would have perhaps required an entire book dedicated to each subject.
So in the end, far from a definitive work, as too many books claim to be nowadays, this
second edition of the “Flying PIC24” is more than ever similar to a private pilot license, a true
license to learn, merely the beginning of an adventure that never ends.
Introduction
The story goes that I badly wanted to write a book about one of the greatest passions in
my life: flying! I wanted to write a book that would convince other engineers like me to
take the challenge and live the dream – learn to fly and become private pilots. The thing is
that I knew the few hours of actual flying experience I had did not qualify me as a credible
expert on the art of flying. So when I had an opportunity to write a book about Microchip’s
new 16-bit PIC24 microcontrollers, I just could not resist the temptation to join the two
things, programming and flying, in one project. After all, learning to fly means following
a well structured process – a journey that allows you to acquire new capabilities and push
beyond your limits. It takes you gradually through a number of both theoretical and practical
subjects, and culminates with the delivery of the Private Pilot License. The pilot license,
though, is really just the beginning of a whole new adventure- a license to learn as they say.
This compares so well to the process of learning new programming skills, or learning to take
advantage of the capabilities of a new microcontroller architecture.
Throughout the book, I will make brief parallels between the two worlds, and in the
references for each chapter I will add, here and there, some suggestions for reading about
flying. I hope I will stimulate your curiosity and, if you had this dream inside you, I will give
you that last final push to help make it happen.
Who Should Read this Book?
This is the part where I am supposed to tell you that you will have a wonderful experience
reading this book; that you will have a lot of fun experimenting with the software and
hardware projects and you will learn about C programming a shiny new 16-bit RISC processor,
practically from scratch. But, in all honesty I cannot! This is only partially true – I really hope
you will have a lot of fun reading it and the experiments are ... “playful” and you should enjoy
them. However you will need quite some preparation and hard work in order to be able to digest
the material I am presenting at a pace that will accelerate rapidly through the first few chapters.
This book is meant for programmers of a basic to intermediate level of experience, but not for
“absolute” beginners; so don’t expect me to start with the basics of the binary numbers, the
hexadecimal notation or the fundamentals of programming. Although, we will briefly review
xix
xx Introduction
the basics of C programming as it relates to the applications for the latest generation of
general-purpose 16-bit microcontrollers, before moving on to more challenging projects. My
assumption is that you, the reader, belong to one of four categories:
l Embedded Control programmer: experienced in assembly-language microcontrollers
programming, but with only a basic understanding of the C language.
l PIC® microcontroller expert: with a basic understanding of the C language.
l Student or professional: with some knowledge of C (or C) programming for PCs.
l Other SLF (superior life forms): I know programmers don’t like to be classified that
easily so I created this special category just for you!
Depending your level and type of experience, you should be able to find something of
interest in every chapter. I worked hard to make sure that every one of them contained both
C programming techniques and new hardware peripherals details. Should you already be
familiar with both, feel free to skip to the experts section at the end of the chapter, or consider
the additional exercises, book references and links for further research/reading.
These are some of the things you will learn:
l The structure of an embedded-control C program: loops, loops and more loops
l Basic timing and I/O operations
l Basic embedded control multitasking in C, using the PIC24 interrupts
l new PIC24 peripherals, in no specific order:
l Input Capture
l Output Compare
l Change Notification
l Parallel Master Port
l Asynchronous Serial Communication
l Synchronous Serial Communication
l Analog-to-Digital conversion
l How to control LCD displays
l How to generate video signals
l How to generate audio signals
l How to access mass-storage media
l How to share files on a mass-storage device with a PC
Structure of the Book
Similar to a flying course, the book is composed of three parts. The first part contains five
small chapters of increasing levels of complexity. In each chapter, we will review one basic
Introduction xxi
hardware peripheral of the PIC24FJ128GA010 microcontroller and one aspect of the C
language, using the MPLAB C30 compiler (Student Version included in the CD-ROM).
In each chapter, we will develop at least one demonstration project. Initially, such projects
will require exclusive use of the MPLAB SIM software simulator (included in the CD-ROM),
and no actual hardware will be necessary; although, an Explorer 16 demonstration board
might be used.
In the second part of the book, containing five more chapters, an Explorer16 demonstration
board (or third-party equivalent) will become more critical, as some of the peripherals used
will require real hardware to be properly tested.
In the third part of the book, there are five larger chapters. Each one of them builds on the
lessons learned in multiple previous chapters, while adding new peripherals to develop
projects of greater complexity. The projects in the third part of the book require the use of the
Explorer 16 demonstration board and basic prototyping skills, too (yes, you might need to use
a soldering iron). If you don’t want to or you don’t have access to basic hardware prototyping
tools, an ad hoc expansion board containing all the circuitry and components necessary to
complete all the demonstration projects will be made available on the companion Web site:
http://www.flyingpic24.com
All the source code developed in each chapter is also available for immediate use on the
companion CD-ROM.
What this Book is Not
This book is not a replacement for the PIC24 datasheet, reference manual and programmer’s
manual published by Microchip Technology. It is also not a replacement for the MPLAB C30
compiler user’s guide, and all the libraries and related software tools offered by Microchip.
Copies are available on the companion CD-ROM, but I expect you to download the most
recent versions of all those documents and tools from Microchip’s Web site (http://www
.microchip.com). Familiarize yourself with them and keep them handy. I will often refer
to them throughout the book, and I might present small block diagrams and other excerpts
here and there as necessary. But, my narration cannot replace the information presented
in the official manuals. Should you notice a conflict between my narration and the official
documentation, ALWAYS refer to the latter. However please send me an email if a conflict
arises, I will appreciate your help and I will publish any correction and useful hint I will
receive on the companion Web site: http://www.flyingpic24.com
This book is also not a primer on the C language. Although a review of the language is
performed throughout the first few chapters, the reader will find in the references several
suggestions on more complete introductory courses and books on the subject.