#define TCNT2_PERIOD_US      1000
#define TCNT2_PRESCALER        64

void initADC()
{
  noInterrupts();
  ADMUX |= (1 << REFS1) | (1 << REFS0);                     // Internal 1.1V Voltage Reference with external capacitor at AREF pin
  ADCSRA |= (1 << ADIE);                                    // Activating ADC Conversion Complete Interrupt
  ADCSRA |= (1 << ADPS2) | (1 << ADPS1) | (1 << ADPS0);     // Division factor between the system clock frequency and the input clock to the ADC set to 128 -> 125 kHz
  while(!(ADCSRA & ADIF));                                  // Wait until first conversion is complete, which takes 200 µs
  interrupts();
}

void initTimer()
{
  noInterrupts();
	TCCR2A |= (1 << WGM21);                                   // set CTC-MODE: WGM21 = 1
  OCR2A = TCNT2_PERIOD_US * F_CPU / 1e6 / TCNT2_PRESCALER; // set Output Compare Register A
	TIMSK2 |= (1 << OCIE2A);                                  // enable Output Compare A Match Interrupt
  TCCR2B |= (1 << CS22);                                    // clkT2S/8 (From prescaler)
  interrupts();
}

unsigned int adc_value = 0;

ISR(ADC_vect)
{
  adc_value = ADC;
}

ISR(TIMER2_COMPA_vect)
{

}

void setup()
{

}

void loop()
{

}