void setup() {
  // put your setup code here, to run once:
  volatile char *dira, *dirb;
  dira = 0x21; dirb = 0x24;
  *dira = 0xFF; *dirb = 0xFF;
  volatile char *outa, *outb;
  volatile long i, j;
    outa = 0x22; outb = 0x25;
  while (1) {
    for (i = 0; i < 8; i++) {
      unsigned char p = 1 << i;
      unsigned char q = 1 << 7 - i;
      *outa = (p); *outb = ~(q);
      *outa = 0x00;
      *outb = ~(0x00);
    }
  }
}

void loop() {
  // put your main code here, to run repeatedly:

}