import processing.serial.*;

Serial myPort;  // Create object from Serial class
int val;      // Data received from the serial port
int state = 0; 
int old_state = 0;

void setup() 
{
  size(200, 200);
  myPort = new Serial(this, "/dev/ttyACM0", 9600);
}

void draw()
{
  if ( myPort.available() > 0) {  // If data is available,
    val = myPort.read();         // read it and store it in val
    background(val);             // Set background to white
    println(val);
  }
  
  if (mouseX > 20 && mouseX < 60 && mouseY > 20 && mouseY < 60) {
    fill(255,0,0);
    state = 1;
  } else {
    fill(255);
    state = 0;
  }

  if (old_state == 0 && state == 1) 
    myPort.write('H');
  if (old_state == 1 && state == 0) 
    myPort.write('L');
  
  rect(20,20,40,40);
  
  old_state = state;
}