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

#define DELAY 1000

int main(void)
{
	// Set PB5 (pin 13) as output
	DDRB |= (1 << DDB5);

	while (1)
	{
		// LED ON
		PORTB |= (1 << PORTB5);
		_delay_ms(DELAY);

		// LED OFF
		PORTB &= ~(1 << PORTB5);
		_delay_ms(DELAY);
	}
}