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


int main (void){
  DDRB |= (1 << PB5);
  PORTB &= ~(1 << PB5);

  while(1){
    PORTB |= (1 << PB5);
    _delay_ms(500);
    PORTB &= ~(1 << PB5);
    _delay_ms(500);
  }
  return 0;
}