#define F_CPU 16000000UL
#include <avr/io.h>
#include <util/delay.h>

int main(void)
{   
    DDRB |= (1<<DDB7); 

    while(1)    // loop forever
    {
        PORTB |=  (1 << PORTB7);  // Turn the LED on.
        _delay_ms(500);
        PORTB &= ~(1 << PORTB7);  // Turn the LED off.
        _delay_ms(500);

    } // while(1)
}