let connectBtn;

​

function setup() {

  createCanvas(400, 400);

  background(220);

​

  port = createSerial();

​

  // setup serial ports

  let usedPorts = usedSerialPorts();

  if (usedPorts.length > 0) {

    port.open(usedPorts[0], 9600);

  }

​

  connectBtn = createButton('Disconnect');

  connectBtn.position((width/2-connectBtn.width/2), height-40);

  connectBtn.mousePressed(connectBtnClick);

}

​

function draw() {

  // reads the incomming value

  let str = port.readUntil("\n");

  if (str.length > 0) {

    background(220);

    text(str, 10, height-20);

    let c = map( str, 0, 1024, 0, width);

    circle(width/2, height/2, c);  

  }

​

  // changes button label based on connection status

  if (!port.opened()) {

    connectBtn.html('_Connect_');

  } else {

    connectBtn.html('Disconnect');

  }

​

}

​

function connectBtnClick() {

  if (!port.opened()) {

    port.open('Arduino', 9600);

  } else {

    port.close();

  }

}