int IN1 = 8;
int IN2 = 9;
int IN3 = 10;
int IN4 = 11;
int demora = 20; // Demora de 20 ms. 

int paso[8][4] = {
  {1,0,0,0},
  {1,1,0,0},
  {0,1,0,0},
  {0,1,1,0},
  {0,0,1,0},
  {0,0,1,1},
  {0,0,0,1},
  {1,0,0,1}
};

void setup() {
  pinMode(IN1, OUTPUT);
  pinMode(IN2, OUTPUT);
  pinMode(IN3, OUTPUT);
  pinMode(IN4, OUTPUT);
}

void loop() {
  for (int i = 0; i < 512; i++){ // 512*8 = 4096 pasos por vuelta.
    for (int j = 0; j < 8; j++){
      digitalWrite(IN1, paso[j][0]);
      digitalWrite(IN2, paso[j][1]);
      digitalWrite(IN3, paso[j][2]);
      digitalWrite(IN4, paso[j][3]);
      delay(demora);
    }
  }
  digitalWrite(IN1, LOW);
  digitalWrite(IN2, LOW);
  digitalWrite(IN3, LOW);
  digitalWrite(IN4, LOW);
  delay(5000);
}