/*
 * main.c
 *
 * Created: 23.4.2013 22:13:52
 *  Author: mpirc
 */ 
#include <avr/io.h>

void Init();
int	ADConvert(char channel);

int main()
{
	int result;
	Init();

	while(1)
	{
		result=ADConvert(2);	//measure channel 2 (trimmer)
		PORTB=result>>2;		//shift the result for 2 bits (lose the 2 least significant bits out of 10) 
	}							//before displaying it on the 8 bit PORTB.
}

void Init()
{
	//IO port
	PORTA=0x08;	//0000 1000
	PORTB=0x00;	//0000 0000
	PORTC=0x3E;	//0011 1110
	PORTD=0x7D;	//0111 1101
	//1-output, 0-input
	DDRA=0xF0;	//1111 0000
	DDRB=0xFF;	//1111 1111
	DDRC=0xC1;	//1100 0001
	DDRD=0x82;	//1000 0010

	//ADC
	ADMUX=(1<<REFS0);				//select 5V power supply as the reference voltage
	ADCSRA=(1<<ADEN) | (7<<ADPS0);	//enable the AD converter and select the 1:128 clock prescaller for the ADC clock
	DIDR0=0x07;						//Disable input buffers on pins PA0 to PA2	
}

int	ADConvert(char channel)
{
	ADMUX = (ADMUX & 0xE0) | (channel & 0x1F);	//select channel (without modifying the other bits in the register)
	ADCSRA |= (1<<ADSC);		//Start conversion
	while (ADCSRA & (1<<ADSC)); //Wait until conversion is completed (ADSC bit changes from 1 to 0 when conversion is done)
	return ADC;					//return the result
}