Elijah - C Programming for Microcontrollers: Featuring ATMEL’s AVR Butterfly and the Free WinAVR Compiler

C Programming for Microcontrollers

Featuring ATMELs AVR Butterfly and the Free WinAVR Compiler

Cosmos Elijah

Table of Contents:
Why
AVR?.........................................................................................................12
Chapter 2: Quick Start Guide................................................................................17
Chapter 3: A Brief Introduction to C What Makes Blinky Blink?.....................39 Functions.......................................................................................................41 The Main() Thing..........................................................................................42
Projects.......................................................................................................... 65 Port Input and Output................................................................................ 65
Statements and Blocks .................................................................................. 73
Switch............................................................................................................ 75
Loops While, For and Do-while................................................................. 78
Break and Continue....................................................................................... 79
A few practical examples: strlen, atoi, itoa, reverse...................................... 81 Chapter 6: C Functions and Program Structures................................................... 87
Variables External, Static, and Register........................................................ 90
Headers.......................................................................................................... 92
Blocks............................................................................................................ 92
Recursion ...................................................................................................... 93
Projects.......................................................................................................... 98 Is anybody out there? Communicating with a PC..................................... 98
Projects........................................................................................................ 114
Calibrating the Butterfly oscillator: ............................................................ 121
Projects........................................................................................................171 Chapter 9 Digital Meets Analog ADC and DAC..........................................207
But First - A Debugging Tale
......................................................................207 Analog to Digital
Conversion .....................................................................210
Projects........................................................................................................216
Structures and Functions.............................................................................243
Projects........................................................................................................251

Table of Figures:
Figure 1: Dennis Ritchie, inventor of the C programming language stands next to Ken Thompson, original inventor of Unix, designing the original Unix

operating system at Bell Labs on a PDP-11.................................................. 11 Figure 2: The Butterfly front................................................................................. 21 Figure 3: RS-232 connections............................................................................... 22 Figure 4: Battery holder, switch, and batteries..................................................... 23 Figure 5: External battery connection to Butterfly ............................................... 23 Figure 6: Butterfly hooked up to RS-232.............................................................. 24 Figure 7: Bray's Terminal...................................................................................... 24 Figure 8: Enter name to send to the Butterfly....................................................... 25 Figure 9: Blinky wiring diagram and photo of wired board................................ 26 Figure 10: Hardware setup for Blinky................................................................... 27 Figure 11: From the cover of the Battlestar Galactica comic Red Cylon .............. 34 Figure 12: from page 92 of the ATMega169 data book........................................ 58 Figure 13 ATMega169 Block Diagram................................................................. 65 Figure 14: Port I/O switch input and LED output................................................. 69 Figure 15: Bit 7 high
Figure 16: Bit 7 low......................................... 71 Figure 17: Pulse Width Modulation Duty Cycle................................................. 134 Figure 18: Motor Speed Control Schematic and Parts........................................ 137 Figure 19: Motor Speed Control Breadboard Labeled........................................ 138 Figure 20: Motor Speed Control Hardware ........................................................ 138 Figure 21: Motor Base ........................................................................................ 139 Figure 22: Motor Wheel Stationary and Spinning.............................................. 139 Figure 23: Opto Interrupt Switch - H21A1......................................................... 145 Figure 24: Opto Interrupter Glued on Motor Base ............................................. 145 Figure 25:
Speedometer...................................................................................... 146 Figure 26: The PDP-11 could be programmed by switches, though Dennis Ritchie used a Teletype machine to write the C programming language................ 153 Figure 27: 10-bit successive approximation ADC Figure................................... 211 Figure 28: Potentiometer Schematic................................................................... 225 Figure 29: Voltage measurement......................................................................... 226 Figure 30: R-2R resistor ladder........................................................................... 228 Figure 31: Breadboard of R-2R DAC................................................................. 228 Figure 32: Breadboard R-2R DAC wiring.......................................................... 229 Figure 33: R-2R DAC with Oscilloscope........................................................... 229 Figure 34: Function Generator / Digital Oscilloscope on HyperTerminal.......... 230 Figure 35: Sine Wave Figure 36: Square Wave..............................................231 Figure 37: Triangle Wave Figure 38: Sawtooth Wave ...................................231

Figure 39 Butterfly Menu....................................................................................253
Figure 40: Cheap soldering iron, solder and wick from JAMECO.....................276 Figure 41: Seasoning the tip................................................................................276

Chapter 1: Introduction

C Programming and microcontrollers are two big topics, practically continental in size, and like continents, are easy to get lost in. Combining the two is a little like traipsing from Alaska to Tierra del Fuego. Chances are youll get totally lost and if the natives dont eat you, your infected blisters will make you want to sit and pout. Ive been down this road so much that I probably have my own personal rut etched in the metaphorical soil, and I can point to all the sharp rocks Ive stepped on, all the branches that have whacked me in the face, and the bushes from which the predators leapt. If you get the image of a raggedy bum stumbling through the jungle, youve got me right. Consider this book a combination roadmap, guidebook, and emergency first aid kit for your journey into this fascinating, but sometimes dangerous world.