AVR A/D example.c

#include <avr/io.h>

void adc_init(void);                                 // A/D converter initialization

int main(void)
{
  unsigned int buffer;

  adc_init();                                         // Init A/D converter

  while (1)
  {
    ADCSRA |= (1<<ADSC);                              // Start A/D conversion
    while ( !(ADCSRA & (1<<ADIF)) /* Do nothing */ ;  // Wait until AD not finished
    buffer = (ADCH<<8) | ADCL;                        // Then, read result
  }

}


void adc_init(void)                                  // A/D converter initialization
{
  ADMUX = 0;                                         // Ref: external, Channel 0 (ADC0)
  ADCSRA = (1<<ADEN)|(1<<ADPS2)|(1<<ADPS1);  	     // A/D ON, prescaler = 64, 
  SFIOR = 0;	                                     // Specialfunctions OFF
}