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

int main()
{
  DDRB = 0b00000001;           // Set PB0 pin mode to OUTPUT
  while(1)
  {
    PORTB = 0b00000001;        // Set PB0 state to HIGH
    _delay_ms(500);            // Delay 500 ms
    PORTB = ~0b00000001;       // Set PB0 state to LOW
    _delay_ms(500);            // Delay 500 ms
  }
}