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


#define LED PB5 // LED is on Pin 13 or Pin 5 of Port B

void initIO(void)
{
DDRB |= (1<<LED);
}


int main(void)
{
  initIO();

  while (1)
  {
   PORTB |= (1<<LED); // set
   _delay_ms(500);
   PORTB &= ~(1<<LED); // clear
   _delay_ms(500);
  }
  return 0; // never reached
}