void config_timer1() {
  TCCR1A = 0;
  TCCR1B = 0;
  TCNT1 = 0;

  // tc = f_cpu / (prescaler * f_needed) - 1 = f_cpu / prescaler * time - 1
  OCR1A = (F_CPU / PRESCALER) * SAMPLING_INTERVAL_S - 1;  // Calculate the compare value

  TCCR1B |= (1 << WGM12);   // CTC mode
  TCCR1B |= (1 << CS12);    // 256 prescaler 
}

void init_timer1() {
  TIMSK1 |= (1 << OCIE1A);  // enable timer compare interrupt
}