#define LED 7

void setup() {
  // put your setup code here, to run once:
  Serial.begin(115200);
  Serial.setTimeout(1000);
  // demo led output 
  pinMode(LED, OUTPUT);    // sets the LED Pin as output
  digitalWrite(LED, LOW);  // initial OFF
}

void loop() {
  String input;
  char any;
  Serial.println("Waiting for command...");

  while (Serial.available() == 0) {
    // you can do something if no data is available
  }     

  String command = Serial.readString();  //read until timeout (see setTimeout line #4 for ms)
  command.trim();                        // remove any \r \n whitespace at the end of the String

  Serial.print("Received command:");
  Serial.println(command);
  
  if (command == "on") {
    digitalWrite(LED, HIGH);
    Serial.println("DONE: Switching ON");
  } 
  else if (command == "off") {
    digitalWrite(LED, LOW);
    Serial.println("DONE: Switching OFF");
  }  
  else {
    Serial.println("Unknown command");
  }
}