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

#define DELAY 50
#define BITS sizeof(PORTB) * CHAR_BIT - 1

int main(void) {
    int i;

    DDRB = 0xff;

    PORTB = 1;

    for (;;) {
        for (i = 0; i < BITS; i++) {
            _delay_ms(DELAY);
            PORTB = PORTB << 1;
        }
        for (i = BITS; i > 0; i--) {
            _delay_ms(DELAY);
            PORTB = PORTB >> 1;
        }
    }

    return 0;
}