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Simple examples

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Do-nothing

A basic C-program for an AVR can look like this:

//Include the default AVR io-header
//This file(avr/io.h) holds all of the information about the mcu's ports, setup-registers and so on 
#include <avr/io.h>
 
//The normal main-routine
int main(void){
   //Our main-loop
   for(;;){
      //Do nothing
   }
   //The compiler requires us to return something, even though we will never get here...
   return 0;
}

This program doesn't really do much however, so lets simply create another program which does a little bit more:

Reading & writing from ports

//Include the default AVR io-header
#include <avr/io.h>
 
//The normal main-routine
int main(void){
 
   //Set PORTB as output
   DDRB = 0xff;
   //Set PORTA as input
   DDRA = 0x00;
 
   //Our main-loop
   for(;;){
      //Set PORTB as PORTA
      PORTB = PINA;
      //Observe that when reading values from a port you use the PINx-tag, when writing values, you use the PORTx-tag.         
   }
   //The compiler requires us to return something, even though we will never get here...
   return 0;
}

Phew, our first program that actually does something! Notice how much this example resembles the first example.

--Oybo 06:06, 31 October 2007 (CET)