LinuxFocus article number 231 http://linuxfocus.org

by Guido Socher (homepage) About the author: Guido loves Linux not only because it is fun to discover the great possibilities of this systems but also because of the people involved in its design.

Programming the AVR Microcontroller with GCC Abstract: Note: An updated version of this article is now available at: ../November2004/article352 The AVR 8-Bit RISC Microcontroller from Atmel is a very common Microcontroller It's a single integrated circuit with EEPROM, Ram, Analog to Digital converter, a lot of digital input and output lines, timers, UART for RS 232 communication and many other things. The best is however that a complete programming environment is available under Linux: You can program this Microcontroller in C using GCC. In this article I will explain how to install and use GCC. I will as well explain how to load the software into the Microcontroller. All you need for this are an AT90S4433 Microcontroller, a 4Mhz crystal, some cable and a few other very cheap parts. This article shall be only an introduction. In a later article we will build a LCD display with a few push buttons, analog and digital inputs, hardware watchdog and LEDs. The idea is that this will be a general purpose control panel for a Linux Server but first we will learn how to setup the programming environment and that is what this article is about. _________________ _________________ _________________

Software installation: What you need

To use the GNU C development environment you need the following software:

mkdir /usr/local/atmel

Software installation: GNU binutils

bunzip2 -c binutils-2.11.2.tar.bz2 | tar xvf -
cd binutils-2.11.2
./configure --target=avr --prefix=/usr/local/atmel
make
make install

Software installation: AVR gcc

tar zxvf gcc-core-3.0.3.tar.gz
cd gcc-core-3.0.3
./configure --target=avr --prefix=/usr/local/atmel --disable-nls --enable-language=c
make
make install

Software installation: The AVR C-library

Set some environment variables (syntax is for bash):
export CC=avr-gcc
export AS=avr-as
export AR=avr-ar
export RANLIB=avr-ranlib
export PATH=/usr/local/atmel/bin:${PATH}

./configure --prefix=/usr/local/atmel --target=avr --enable-languages=c --host=avr
make
make install

Software installation: The Programmer

tar zxvf uisp-20011025.tar.gz
cd uisp-20011025/src
make
cp uisp /usr/local/atmel/bin

A small test project

Needed Hardware

	1 x AT90S4433, Atmel 8 bit Avr risc processor.
	2 x 14 pin IC socket or 1 x 28 pin 7.5mm IC socket The 28 pin socket is a bit more difficult to get. Usually the 28 sockets are 14mm wide but we need a 7.5mm socket.
	1 x 10K resistor (color code: brown,black,orange) 3 x 470 Ohm resistor (color code: yellow,purple,brown) 1 x 1K resistor (color code: brown,black,red) 1 x 220 Ohm resistor (color code: red,red,brown) 1 x 4Mhz Crystal 2 x 27pf ceramic capacitor
	Any kind of 5 pin connector/socket for the programmer. I usually buy these strips of connectors and break off 5 of them.
	matrix board
	1 x DB25 connector to plug into the parallel port.
	1 x LED
	A breadboard. We don't use it here but it is very useful if you want to do further experiments with the AVR. I suggest you leave the Microcontroller together with the crystal and the capacitors on the matrix board and connect the input/output lines via short cables to the breadboard.

Building the programmer hardware

Writing software

void main(void)
{
      /* enable PD5 as output */
      sbi(DDRD,PD5);
      while (1) {
            /* led on, pin=0 */
            cbi(PORTD,PD5);
            delay_ms(500);
            /* set output to 5V, LED off */
            sbi(PORTD,PD5);
            delay_ms(500);
      }
}

Compiling and loading

export PATH=/usr/local/atmel/bin:${PATH} (for bash)
setenv PATH /usr/local/atmel/bin:${PATH} (for tcsh)

# /sbin/lsmod
parport_pc
ppdev
parport

modprobe parport
modprobe parport_pc
modprobe ppdev

chmod 666 /dev/parport0

Some interesting binutils

avr-objdump -h avrledtest.out

avrledtest.out:     file format elf32-avr

Sections:
Idx Name          Size      VMA       LMA       File off  Algn
  0 .text         0000008c  00000000  00000000  00000094  2**0
                  CONTENTS, ALLOC, LOAD, READONLY, CODE
  1 .data         00000000  00800060  0000008c  00000120  2**0
                  CONTENTS, ALLOC, LOAD, DATA
  2 .bss          00000000  00800060  0000008c  00000120  2**0
                  ALLOC
  3 .eeprom       00000000  00810000  00810000  00000120  2**0
                  CONTENTS
  4 .stab         00000750  00000000  00000000  00000120  2**2
                  CONTENTS, READONLY, DEBUGGING
  5 .stabstr      000005f4  00000000  00000000  00000870  2**0
                  CONTENTS, READONLY, DEBUGGING

avr-size avrledtest.out

   text    data     bss     dec     hex filename
    140       0       0     140      8c avrledtest.out

avr-objdump -S avrledtest.out

Conclusion

References

• Libc and uisp: /www.amelek.gda.pl/avr/libc/
• GCC and binutils: ftp://gatekeeper.dec.com/pub/GNU/
• avrfreaks (watch out some people on that site are still using windows !?): http://www.avrfreaks.net/
• the tavrasm assembler for Linux: www.tavrasm.org
• AVR webring: R.webring.com/hub?ring=avr&list
• Pre-compiled versions of gcc: combio.de/avr/
• All software and documents mentioned in this article
• The atmel website: www.atmel.com/

2005-01-14, generated by lfparser_pdf version 2.51