void setup() {
  Serial.begin(115200);

  pinMode(8, OUTPUT); // !Enable

  pinMode(2, OUTPUT); // A-step
  pinMode(5, OUTPUT); // A-dir

  pinMode(3, OUTPUT); // B-step
  pinMode(6, OUTPUT); // B-dir

  pinMode(4, OUTPUT); // C-step
  pinMode(7, OUTPUT); // C-dir

  pinMode(12, OUTPUT); // D-STEP
  pinMode(13, OUTPUT); // D-DIR

  // PIND is the input register of port D (pins 0 to 7 on the UNO)
  PIND = 0b10100000; // Reverse direction AB


}

void loop() {
  PIND = 0b11100;
  // PINB is the input register of port D (pins 8 to 13 on the UNO)
  PINB = bit(4);

  delay(100);
  delayMicroseconds(35);
}