2.1. Licence

      Permission is granted to copy, distribute, and/or modify this
      document under the terms of the GNU Free Documentation License,
      Version 1.2, or any later version published by the Free Software
      Foundation; with no Invariant Sections, no Front-Cover Texts, and
      no Back-Cover Texts.  A copy of the license is included in the
      section entitled "GNU Free Documentation License".

GNU Free Documentation License

2.2. What Is a Microcontroller?

A microcontroller is a single-chip computer. It has internal RAM, ROM, timers, counters, interrupt circuitry, I/O ports, analog comparators, serial USARTs, analog to digital converters, watchdog timers, and a RISC architecture. When you are using a microprocessor, you cannot program it alone. You need other components, like RAM, ROM, timers, etc. For programming, you should know its architecture thoroughly: You must read the datasheet for your microcontroller.

2.3. Software Required

binutils: Tools like the assembler, linker, etc.

gcc-avr: The GNU C compiler (cross-compiler for avr).

avr-libc: Package for the AVR C library, containing many utility functions.

uisp: A Micro In-System Programmer for Atmel's AVR MCUs (for burning code to MCUs' memory).

The following Atmel microcontrollers are supported by avr-gcc in Linux:

at90s Type Devices

at90s2313, at90s2323, at90s2333, at90s2343, at90s4414, at90s4433, at90s4434, at90s8515, at90s8515, at90s8515, at90s8535, at90s1200.

atmega Type Devices

atmega103, atmega603, atmega8, atmega48, atmega88, atmega8515, atmega8535, atmega16, atmega161, atmega162, atmega163, atmega165, atmega168, atmega169, atmega32, atmega323, atmega325, atmega3250, atmega64, atmega645, atmega6450, atmega128.

attiny Type Devices

attiny22, attiny26, attiny26, attiny13, attiny13, attiny13, attiny13, attiny2313, attiny11, attiny12, attiny15, attiny28.

Other AVR Devices

avr2, at90c8534, at86rf401, avr3, at43usb320, at43usb355, at76c711, avr4, avr5, at90can128, at94k, avr1.

binutils: Programs to manipulate binary and object files that may have been created for Atmel's AVR architecture. This package is primarily for AVR developers and cross-compilers.

gcc-avr: The GNU C compiler, a fairly portable optimising compiler that supports multiple languages. This package includes C language support.

avr-libc: Standard library used for developing C programs for Atmel AVR microcontrollers. This package contains static libraries, as well as needed header files.

uisp: Utility to program AVR chips with object code created by gcc-avr. It supports in-system programming.

You download the above packages untar, configure, and install it. If you are using Debian or Ubuntu, these packages are available in your distribution: Install them using apt or synaptic package manager.

2.4. Hello World

We are writing hello world for the atmega8 microcontroller, which has a 28-pin, 8-bit, RISC architecture.

Before proceeding, have a look at this manual about __avr-libc__, which will help you program better, and understand. Also, refer to the datasheets for the various AVR microcontrollers.

Here is our first program:

/* ledblink.c, an LED blinking program */
#include<avr/io.h>
#include<util/delay.h>
void sleep(uint8_t millisec)
{
        while(millisec)

        {
                _delay_ms(1);/* 1 ms delay */
                millisec--;
        }
}
main()
{

        DDRC |=1<<PC2;  /* PC2 will now be the output pin */
        while(1)
        {
                PORTC &= ~(1<<PC2);/* PC2 LOW */
                sleep(100);/* 100 ms delay */

                PORTC |=(1<<PC2); /* PC2 HIGH */
                sleep(100);/* 100 ms delay */
        }
}

avr-gcc -mmcu=atmega8 Os ledblink.c o ledblink.o

avr-objcopy -j .text -j .data -O ihex  ledblink.o  ledblink.hex

:1000000012C02BC02AC029C028C027C026C025C0C6
:1000100024C023C022C021C020C01FC01EC01DC0DC
:100020001CC01BC01AC011241FBECFE5D4E0DEBF28
:10003000CDBF10E0A0E6B0E0EAE8F0E002C0059035
:100040000D92A036B107D9F710E0A0E6B0E001C0EC
:100050001D92A036B107E1F70CC0D2CF282FE4ECF7
:10006000F9E004C0CF010197F1F721502223D1F725
:100070000895CFE5D4E0DEBFCDBFA29AAA9884E66A

:0A008000EDDFAA9A84E6EADFF9CF6B
:00000001FF

uisp -dprog=dapa -dlpt=0x378

uisp -dprog=dapa -dlpt=0x378 --erase

uisp -dprog=dapa -dlpt=0x378 --upload if=ledblink.hex

2.5. Author

Comments to: mailto:ranjeeth_gecmail[at]yahoo[dot]com

Ranjeeth Weblog

Govt Engg College Sreekrishnapuram,

Palakkad,Kerala India.

2.6. Last version

You may find the last up-to-date version of this HOWTO on the LDP wiki.