#include <avr/io.h>
#include <util/delay.h>

static inline void initADC0(void) {
  ADMUX |= (1 << REFS0);
  ADCSRA |= (1 << ADPS2) | (1 << ADPS1) | (1 << ADPS0);
  ADCSRA |= (1 << ADEN);
  ADCSRA |= (1 << ADIE);
}

ISR (ADC_vect) {
  //Serial.println(ADC);
  float adcValue = ADC;
  float voltageOutput = (5 * adcValue) / 1023;
  //Serial.println(adcValue);
  //Serial.println(voltageOutput);
  if (voltageOutput < 2.5) {
    PORTB |= (1 << PB0);
  }
  else if (voltageOutput >= 2.5) {
    PORTB &= ~(1 << PB0);
  }
  ADCSRA |= (1 << ADSC);
}

int main (void) {
  Serial.begin(9600);
  initADC0();
  sei();
  DDRB = 0xff;

  ADCSRA |= (1 << ADSC);
  while (1) {
    PORTB ^= (1 << PB1);
    //Serial.println(bitRead(PORTB,PB1));
    _delay_ms(1000);
  }
  return (0);
}