// Definition of interrupt names
#include <avr/io.h>
// ISR interrupt service routine
#include <avr/interrupt.h>
const int pLED = 13; // LED at Pin13
const int pAIN2 = 6; // AIN2 at Pin6
const int pAIN1 = 7; // AIN1 at Pin7
volatile boolean iflag = true;
int idx;

// Install the interrupt routine for ACOMP
ISR(ANALOG_COMP_vect)
{
  Serial.println("Hi");
  if ( ACSR & (1<<ACO) ) // ACO is set?
  {
    iflag = false;
    digitalWrite(pLED, HIGH);
  }
  else
  {
    iflag = true;
    digitalWrite(pLED, LOW);
  }
}

void setup()
{
  Serial.begin(9600);
  pinMode(pLED, OUTPUT);
  digitalWrite(pLED, LOW);
  pinMode(pAIN1, INPUT);
  pinMode(pAIN2, INPUT);
  cli();
  
  ADCSRB &= ~(1<<ACME); // AMUX disabled
  ACSR = (1<<ACIE); // ACOMP Interrupt enabled
  DIDR1 = (1<<AIN1D) | (1<< AIN0D);
  
  sei();
  
  Serial.print("ADCSRA: "); Serial.println(ADCSRA, HEX);
  Serial.print("ADCSRB: "); Serial.println(ADCSRB, HEX);
  Serial.print("ACSR: "); Serial.println(ACSR, HEX);
  Serial.print("DIDR1: "); Serial.println(DIDR1, HEX);
  Serial.println("Setup finished.");
}

void loop()
{
  /*if (iflag) 
    Serial.println(idx); // iflag controls serial output
  idx++;
  delay(500);*/
}