float photoVal;
const int ledPIN  = 7;

void setup()
{
  Serial.begin(9600);
  enableADC();
  PORTD |= (1<<2); // internal pullup pin 2
  pinMode(ledPIN, OUTPUT);
  timerInterrupt();
  setButtonInterrupt();
}

void loop()
{

  delay(1000);

}

//timer interrrupt
ISR(TIMER1_COMPA_vect) {

  static byte state = LOW;
  static int counter = 0;
  counter++;
  if (counter >= photoVal)
  {
  state = !state;
  digitalWrite(ledPIN, state);
  counter = 0;
  }

}
//button interrupt
ISR(INT0_vect) {
  photoVal = manualAnalogRead() + 100; // legger til 100 for å gi en minsteverdi
  Serial.print(photoVal);
  Serial.print("\n");
}



void timerInterrupt() {
  cli();
  //Clear registers
  TCCR1A = 0;
  TCCR1B = 0;
  TCNT1 = 0;

  //Timer control B
  //Set timer speed (prescaler)
  TCCR1B |=  (1 << CS12);
  //Enable timer compare mode
  TCCR1B |= (1 << WGM12);

  //Set compare value
  OCR1A = 16000000 / 256 / 1000;

  //Enable compare interrupt
  TIMSK1 |= (1 << OCIE1A);

  sei();
}

void setButtonInterrupt() {
  cli();
  EICRA = (1 << ISC01); //ISC00 = CHANGE, ISC01 = FALLING(?)
  EIMSK |= (1 << INT0); //INT0 = PIN 2
  sei();
}

float manualAnalogRead()
{

  ADCSRA |= (1 << 6);
  while (ADCSRA & (1 << 6));

  int val = ADCL;
  val |= (ADCH << 8);



  float r = val + 0.00;

  return r;
}
void enableADC() {
  //Setter bit 7 til 1
  ADCSRA |= (1 << 7);

  //XXXX0000 = A0
  ADMUX &= ~0xF;

  //bit 6 aka REFS0 til 1, intern reference
  ADMUX |= (1 << 6);
}