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

int main()
{
  DDRB = (1<<DDB5);
  PORTB = 0;

  TCCR0A = 1<<WGM01;
  TCCR0B = (1<<CS01);
  OCR0A = 5999;
  TIMSK0 = 1<<OCIE0A;
  sei();

  while(1)
  {
    ;;
  }
}

ISR (TIMER0_COMPA_vect)
{
  PORTB = PORTB ^ (1<<PORTB5);
}