let lastValue = 0;

​

function setup() {

  createCanvas(400, 400);

  port = createSerial();

}

​

function draw() {  

  background(220);

  fill(lastValue / 4);

  ellipse(200, 200, 200, 200);

​

  let received = port.readUntil("\n");

  if (received) {

    console.log(received);

    lastValue = parseInt(received);

  }

}

​

function mousePressed() {

  if (!port.opened()) {

    port.open('Arduino', 9600);

  }

}