uint8_t LEDpin = D0;
bool LEDstatus = LOW;

// Set up the serial connection
void setup() {
  Serial.begin(115200);
  pinMode(LEDpin, OUTPUT);
  digitalWrite(LEDpin, LOW);
  Serial.println("Ready. Type 'on' or 'off'.");
}

// Loop to monitor serial connection
// When receiving an appropriate 'on' or 'off'
// it will change the state of the LED
void loop() {
  if (Serial.available()) {
    String command = Serial.readStringUntil('\n');
    command.trim();
    if (command == "on") {
      LEDstatus = HIGH;
      digitalWrite(LEDpin, HIGH);
      Serial.println("LED is ON");
    } else if (command == "off") {
      LEDstatus = LOW;
      digitalWrite(LEDpin, LOW);
      Serial.println("LED is OFF");
    } else {
      Serial.println("Unknown command. Use 'on' or 'off'.");
    }
  }
}