#define LED 23
void setup() {
  Serial.begin(4095);
  pinMode(LED,OUTPUT);
}

void loop() {
  if (Serial.available())
  {
    String command = Serial.readStringUntil('\n');
    if (command == "ON")
    {
      digitalWrite(LED,HIGH);
      Serial.println("turn LED ON");
    }
    else if(command == "OFF")
    {
      digitalWrite(LED,LOW);
      Serial.println("Turn LED OFF");
      }
      }
}