#include <avr/io.h>

void init(void);

void init(void) {
    /* Setup comparator */
    ACSR = (1 << ACIE);
    /* Initialize PORTD for PIND5 */
    DDRD = 0x00;
    PORTD = 0x00;
    /* Enable global interrupts */
    sei();
}

int main(void) {

    init();

    while (1) {}
}

ISR(ANALOG_COMP_vect) {
    PORTC ^= (1 << PINC1);

     if (!(ACSR &  (1<<ACIS0))) { //comparator falling edge
         /* Set PIND5 to 0V */
         PORTD &= ~(1 << PIND5);

         ACSR |= (1<<ACIS0); //set next comparator detection on rising edge
 }
 else  {
        ACSR &= ~(1<<ACIS0); //set next comparator detection on falling edge
        /* Set PIND5 to 5V */
        PORTD |= (1 << PIND5);
    }
}