Beginning C for Arduino Learn C Programming for the Arduino and Compatible Microcontrollers Technology in AcTion™ Beginning C harness the processing power of the microcontroller and learn how Also available: to control your own electronic devices with Beginning C for Arduino. Written for individuals who have no prior experience with microcontrollers or programming, this book teaches you tried and true coding practices that B will help you become a fearless tinkerer. e led by an engaging, expert programmer, with more than 25 years of g university teaching experience, you’ll discover how to use the c program- Arduino ming language to control the Arduino (Atmel) family of microcontrollers i n for as well as Arduino-compatible boards. each step of the way, a simple, inexpensive, hardware experiment demonstrates the language in action. n This provides you with a deep understanding of what the code is doing i and how it is done. n g With Beginning C for Arduino, you’ll learn how to: Learn C Programming for the Arduino C • Use the syntax of the c programming language as defined for the Arduino • Design, code, and debug programs that drive Arduino microcontrollers f and Compatible Microcontrollers • extend the functionality of c by creating your own library routines o • Detect, isolate, and fix program bugs r • implement multiple solutions for any given programming problem A • integrate low-cost, off-the-shelf, hardware shields into your own projects r d Beginning C for Arduino blends a software and hardware learning experi- u Take complete control of your Arduino ence into a single, enjoyable endeavor. it offers you an engaging, take-at- with the power of C your-own-pace way to learn the fundamental programming concepts that i n will fuel your future creations. o P u r d US $39.99 u m Shelve in Computer Hardware/General User level: Beginning-Intermediate SOURCE CODE ONLINE Ph.D. Jack Purdum www.apress.com Beginning C for Arduino n n n Jack Purdum Beginning C for Arduino Copyright © 2012 by Jack Purdum All rights reserved. No part of this work may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or by any information storage or retrieval system, without the prior written permission of the copyright owner and the publisher. ISBN-13 (pbk): 978-1-4302-4776-0 ISBN-13 (electronic): 978-1-4302-4777-7 Trademarked names, logos, and images may appear in this book. Rather than use a trademark symbol with every occurrence of a trademarked name, logo, or image we use the names, logos, and images only in an editorial fashion and to the benefit of the trademark owner, with no intention of infringement of the trademark. The use in this publication of trade names, trademarks, service marks, and similar terms, even if they are not identified as such, is not to be taken as an expression of opinion as to whether or not they are subject to proprietary rights. 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For detailed information about how to locate your book’s source code, go to http://www.apress.com/source-code/. ii To Jane for her unwavering support during this project. iii Contents at a Glance  About the Author ................................................................................................................xiii  About the Technical Reviewer ............................................................................................xiv  Acknowledgments ...............................................................................................................xv  Introduction ........................................................................................................................xvi  Chapter 1: Introduction .........................................................................................................1  Chapter 2: Arduino C ...........................................................................................................21  Chapter 3: Arduino C Data Types ........................................................................................37  Chapter 4: Decision Making in C .........................................................................................55  Chapter 5: Program Loops in C ...........................................................................................77  Chapter 6: Functions in C ....................................................................................................91  Chapter 7: Storage Classes and Scope .............................................................................113  Chapter 8: Introduction to Pointers ..................................................................................131  Chapter 9: Using Pointers Effectively ...............................................................................151  Chapter 10: Structures, Unions, and Data Storage ...........................................................171  Chapter 11: The C Preprocessor and Bitwise Operations ................................................197  Chapter 12: Arduino Libraries ...........................................................................................211  Appendix A: Suppliers and Sources..................................................................................231  Appendix B: Electronic Components for Experiments .....................................................237  Answers to Exercises ........................................................................................................241  Index ..................................................................................................................................257 iv Contents  About the Author ................................................................................................................xiii  About the Technical Reviewer ............................................................................................xiv  Acknowledgments ...............................................................................................................xv  Introduction ........................................................................................................................xvi  Chapter 1: Introduction .........................................................................................................1 Assumptions About You ..........................................................................................................2 What You Need .......................................................................................................................3 An Atmel-Based Microcontroller Card ............................................................................................................3 Breadboard .....................................................................................................................................................5 Miscellaneous Parts .......................................................................................................................................6 Verifying the Software ............................................................................................................6 Verifying the Hardware ...........................................................................................................8 Attaching the USB Cable .................................................................................................................................8 Selecting Your mc Board in the Integrated Development Environment ...........................................................9 Port Selection ...............................................................................................................................................10 Loading and Running Your First Program ............................................................................13 The Blink Program .......................................................................................................................................14 Running the Blink Program Code ..................................................................................................................16 Compiling the Blink Program Code ...............................................................................................................17 Uploading the Blink Program .......................................................................................................................18 Summary ..............................................................................................................................20  Chapter 2: Arduino C ...........................................................................................................21 The Building Blocks of All Programming Languages ............................................................21 Expressions ..................................................................................................................................................21 v ■ contents Statements ...................................................................................................................................................23 Statement Blocks .........................................................................................................................................24 Function Blocks ............................................................................................................................................25 The Five Program Steps .......................................................................................................26 1. Initialization Step ......................................................................................................................................26 2. Input Step .................................................................................................................................................26 3. Process Step .............................................................................................................................................26 4. Output Step ...............................................................................................................................................27 5. Termination Step .......................................................................................................................................27 The Purpose of the Five Program Steps .......................................................................................................27 A Revisit to the Blink Program ..............................................................................................28 Program Comments ......................................................................................................................................29 Data Definition ..............................................................................................................................................30 The setup() Function ....................................................................................................................................32 The loop() Function ......................................................................................................................................34 Summary ..............................................................................................................................35 Exercises ..............................................................................................................................36  Chapter 3: Arduino C Data Types ........................................................................................37 Keywords in C ...............................................................................................................................................38 Variable Names in C .....................................................................................................................................38 The boolean Data Type .........................................................................................................39 The char Data Type ...............................................................................................................39 Binary Data ...................................................................................................................................................39 The char Data Type and Character Sets ........................................................................................................40 Generating a Table of ASCII Characters ........................................................................................................41 The byte Data Type ...............................................................................................................42 The int Data Type ..................................................................................................................43 The word Data Type ..............................................................................................................43 The long Data type ...............................................................................................................43 The float and double Data Types ..........................................................................................43 Floating Point Precision ................................................................................................................................44 The string Data Type .............................................................................................................44 String Data Type ...................................................................................................................45 The void Data Type ...............................................................................................................46 The array Data Type ..............................................................................................................47 vi ■ contents Defining versus Declaring Variables .....................................................................................47 Symbol Tables ...............................................................................................................................................47 lvalues and rvalues .......................................................................................................................................48 The Bucket Analogy ......................................................................................................................................50 Using the cast Operator ........................................................................................................52 Summary ..............................................................................................................................53 Exercises ..............................................................................................................................54  Chapter 4: Decision Making in C .........................................................................................55 Relational Operators .............................................................................................................55 The if Statement ...................................................................................................................56 A Modified Blink Program .....................................................................................................58 The Circuit ....................................................................................................................................................59 The Program Code ........................................................................................................................................60 Software Modifications to the Alternate Blink Program ...................................................61 The if-else Statement ...........................................................................................................62 Cascading if Statements ......................................................................................................63 The Increment and Decrement Operators ............................................................................65 Two Types of Increment Operator (++) .........................................................................................................65 Two Flavors of the Decrement Operator (--) .................................................................................................66 Precedence of Operators ..............................................................................................................................66 The switch Statement ..........................................................................................................67 The goto Statement .............................................................................................................68 Getting Rid of Magic Numbers .............................................................................................68 The C Preprocessor .............................................................................................................68 Heads or Tails .......................................................................................................................71 Initialization Step ..........................................................................................................................................71 Input Step .....................................................................................................................................................71 Process Step .................................................................................................................................................71 Output Step ...................................................................................................................................................71 Termination Step ..........................................................................................................................................72 Something to Think About ....................................................................................................74 Summary ..............................................................................................................................75 Exercises ..............................................................................................................................76 vii ■ contents  Chapter 5: Program Loops in C ...........................................................................................77 The Characteristics of Well-Behaved Loops .........................................................................77 Condition 1: Variable Initialization .................................................................................................................77 Condition 2: Loop Control Test .....................................................................................................................78 Condition 3: Changing the Loop Control Variable’s State .............................................................................78 Using a for Loop ...................................................................................................................78 The while Loop .....................................................................................................................80 The do-while Loop ................................................................................................................81 The break and continue Keywords .......................................................................................82 The break Statement ...................................................................................................................................82 The continue Statement ...............................................................................................................................83 A Complete Code Example ...................................................................................................84 Step 1. Initialization ......................................................................................................................................85 Step 2. Input .................................................................................................................................................85 Step 3. Process ............................................................................................................................................85 Step 4. Output ...............................................................................................................................................85 Step 5. Termination .......................................................................................................................................85 Listing 5-1 is Sorta Dumb Code ....................................................................................................................87 Loops and Coding Style ........................................................................................................88 Summary ..............................................................................................................................89 Exercises ..............................................................................................................................90  Chapter 6: Functions in C ....................................................................................................91 The Anatomy of a Function ..................................................................................................92 Function Type Specifier ................................................................................................................................92 Function Name .............................................................................................................................................92 Function Arguments .....................................................................................................................................93 Function Body ...............................................................................................................................................94 Function Signature ......................................................................................................................................95 What Makes a “Good” Function ...........................................................................................96 Functions Use Task-Oriented Names ............................................................................................................96 The Function Should Be Cohesive ................................................................................................................96 Functions Should Avoid Coupling .................................................................................................................97 Writing Your Own Functions .................................................................................................97 Function Design Considerations ...................................................................................................................98 Argument List ...............................................................................................................................................99 viii ■ contents Function Body ...............................................................................................................................................99 Logical Operators ...............................................................................................................100 Logical AND Operator (&&) ..........................................................................................................................100 Logical OR (||) ..............................................................................................................................................101 Logical NOT (!) ............................................................................................................................................101 Writing Your Function .........................................................................................................102 The IsLeapYear() Function and Coding Style ..............................................................................................103 Arguments versus Parameters ...................................................................................................................103 Why Use a Specific Function Style? ...........................................................................................................104 Leap Year Calculation Program .........................................................................................104 Passing Data Into and Back From a Function .....................................................................107 Pass by Value ..............................................................................................................................................108 Summary ............................................................................................................................110 Exercises ............................................................................................................................111  Chapter 7: Storage Classes and Scope .............................................................................113 Hiding Your Program Data ..................................................................................................113 Statement Block Scope ......................................................................................................113 Local Scope ........................................................................................................................116 Name Collisions and Scope ........................................................................................................................117 Global Scope .......................................................................................................................119 Global Scope and Name Conflicts ...............................................................................................................121 Scope and Storage Classes ................................................................................................121 The auto Storage Class ...............................................................................................................................121 The register Storage Class .........................................................................................................................121 The static Storage Class .............................................................................................................................122 The extern Storage Class ............................................................................................................................122 The volatile keyword ..........................................................................................................127 Summary ............................................................................................................................128 Exercises ............................................................................................................................129  Chapter 8: Introduction to Pointers ..................................................................................131 Defining a Pointer ...............................................................................................................131 Pointer Name ..............................................................................................................................................131 Asterisk ......................................................................................................................................................132 Pointer Type Specifiers and Pointer Scalars ...............................................................................................132 Using a Pointer ...................................................................................................................136 ix