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

volatile unsigned int ValPot;

//---------------------------------
// Lecture de l'ADC 2 sur la pin 4
//---------------------------------
void analogRead() {
  ADMUX = _BV(ADLAR) | _BV(MUX1);     // left shift result and use ADC2 for pot
  ADCSRA |= _BV(ADSC);                // Start conversion
  while (ADCSRA & _BV(ADSC)) {};      // Wait until conversion is done
  ValPot = ADCH << 3;                 // ADCH * 8

  if (ValPot > 2000)                  // Shaping ADC reading
    ValPot = 2000;
}

//-----------------------------
// Interruption mode CTC à 50Hz
//-----------------------------
ISR(TIM0_COMPA_vect) {
  PORTB |= (1<<PB0);                   // Pin 0 high
  _delay_loop_2(ValPot + 2000);        // Wait
  PORTB &= ~(1<<PB0);                  // Pin 0 low
} 

//--------------------
// Programme principal
//--------------------
int main (void) {
  sei();                               // Enable global interrupts
  DDRB |= (1<<PB0) | (1<<PB1);         // PB0 and PB1 as outputs
  TCCR0A |= (1<<WGM01);                // Configure timer 0 for CTC mode
  TIMSK |= (1<<OCIE0A);                // Enable CTC interrupt
  TCCR0B |= (1<<CS02) | (1<<CS00);     // Prescaler clk/1024
  OCR0A = 156;                         // Set CTC to execute at 50Hz
  ADCSRA |= _BV(ADEN) | _BV(ADPS1) | _BV(ADPS0); // ADC Enable and prescaler div 8
  ValPot = 0;                          // Initialize potentiometer reading

  while (1) {
    analogRead();                      // Read pot value and update ValPot
  }
}