void setup() {
  // put your setup code here, to run once:
  Serial.begin(115200);
pinMode(23, OUTPUT);
pinMode(22, OUTPUT);
pinMode(21, OUTPUT);
}

void loop() {
digitalWrite(23, HIGH);
delay(1000);
digitalWrite(23, LOW);
delay(500);
digitalWrite(22, HIGH);
delay(1000);
digitalWrite(22, LOW);
delay(500);
digitalWrite(21, HIGH);
delay(1000);
digitalWrite(21, LOW);
delay(500);
}