#include <avr/io.h>           // this contains all the IO port definitions
#include <util/delay.h>

#define DELAY 125             // 125ms * 8 = 1 seconds

void display(int v) {
    PORTB = v;
    _delay_ms(DELAY);
}

int main (void) {
  DDRB = 0x1F;                // output: 0, 1, 2, 3, 4

  while (1) {
    display(0x01);
    display(0x02);
    display(0x04);
    display(0x08);
    display(0x10);
    display(0x08);
    display(0x04);
    display(0x02);
  }

  return 0;
}