// Arduino IDE:
// File -> Examples -> 04.Communication -> PhysicalPixel
// Source: https://stackpython.medium.com/today-ive-made-a-really-simple-project-the-main-idea-of-this-project-is-to-build-a-gui-app-to-c5884263971c

const int ledPin = 13; // pin the LED is attached to
int incomingByte;      // variable stores  serial data

void setup() {
  // initialize serial communication:
  Serial.begin(9600);
  // initialize the LED pin as an output:
  pinMode(ledPin, OUTPUT);
}

void loop() {
  // see if there's incoming serial data:
  if (Serial.available() > 0) {
    // read the oldest byte in the serial buffer:
    incomingByte = Serial.read();
    // if it's a capital H (ASCII 72), turn on the LED:
    if (incomingByte == 'H') {
      digitalWrite(ledPin, HIGH);
      Serial.println("Getting H"); //print out to serial monitor to check state
    }
    // if it's an L (ASCII 76) turn off the LED:
    if (incomingByte == 'L') {
      digitalWrite(ledPin, LOW);
      Serial.println("Getting L"); //print out to serial monitor to check state
    }
  }
}