const serial = new p5.WebSerial();

// HTML button object:

let portButton;

let inData; // for incoming serial data

let outData; // for outgoing data

​

// variables for the circle to be drawn:

let locH, locV;

let circleColor = 255;

function setup() {

  createCanvas(400, 300); // make the canvas

  // check to see if serial is available:

  if (!navigator.serial) {

    alert("WebSerial is not supported in this browser. Try Chrome or MS Edge.");

  }

  // if serial is available, add connect/disconnect listeners:

  navigator.serial.addEventListener("connect", portConnect);

  navigator.serial.addEventListener("disconnect", portDisconnect);

  // check for any ports that are available:

  serial.getPorts();

  // if there's no port chosen, choose one:

  serial.on("noport", makePortButton);

  // open whatever port is available:

  serial.on("portavailable", openPort);

  // handle serial errors:

  serial.on("requesterror", portError);

  // handle any incoming serial data:

  serial.on("data", serialEvent);

  serial.on("close", makePortButton);

}

function draw() {

  background(0);// black background

  fill(circleColor);// fill depends on the button

  ellipse(locH, locV, 50, 50); // draw the circle

}

// if there's no port selected, 

// make a port select button appear:

function makePortButton() {

  // create and position a port chooser button:

  portButton = createButton('choose port');

  portButton.position(10, 10);

  // give the port button a mousepressed handler:

  portButton.mousePressed(choosePort);

}

// make the port selector window appear:

function choosePort() {

  serial.requestPort();

}

// open the selected port, and make the port 

// button invisible:

function openPort() {

  // wait for the serial.open promise to return,

  // then call the initiateSerial function

  serial.open().then(initiateSerial);

  // once the port opens, let the user know:

function initiateSerial() {

   console.log("port open");

   // send a byte to start the microcontroller sending:

   serial.print("x");

 }

  // hide the port button once a port is chosen:

  if (portButton) portButton.hide();

}

function serialEvent() {

  // read a string from the serial port

  // until you get carriage return and newline:

  var inString = serial.readStringUntil("\r\n");

  //check to see that there's actually a string there:

  if (inString) {

    if (inString !== "hello") {

      // if you get hello, ignore it

      // split the string on the commas:

      var sensors = split(inString, ",");

      if (sensors.length > 2) {

        // if there are three elements

        // element 0 is the locH:

        locH = map(sensors[0], 0, 1023, 0, width);

        // element 1 is the locV:

        locV = map(sensors[1], 0, 1023, 0, height);

        // element 2 is the button:

        circleColor = 255 - sensors[2] * 255;

        // send a byte back to prompt for more data:

        serial.print('x');

      }

    }

  }

}

// pop up an alert if there's a port error:

function portError(err) {

  alert("Serial port error: " + err);

}

// try to connect if a new serial port 

// gets added (i.e. plugged in via USB):

function portConnect() {

  console.log("port connected");

  serial.getPorts();

}

// if a port is disconnected:

function portDisconnect() {

  serial.close();

  console.log("port disconnected");

}