int actPin = 0; void setup() { pinMode(3, OUTPUT); pinMode(1, OUTPUT); pinMode(0, OUTPUT); pinMode(2, OUTPUT); digitalWrite(0, LOW); digitalWrite(1, LOW); digitalWrite(2, LOW); digitalWrite(3, LOW); } void loop() { digitalWrite(actPin, LOW); if (actPin == 3) { actPin = 0; } else { actPin ++; } digitalWrite(actPin, HIGH); delay(2000); }