let portName = '/dev/tty.usbserial-1410';  // fill in your serial port name here

let inData,outData;

function setup() {

  createCanvas(300,300);

  serial = new p5.SerialPort();       

  serial.on('data', serialEvent);     

  serial.on('error', serialError);    

  serial.open(portName);             

}

​

function draw(){

  background(200);

  outData=map(mouseY,0,height,0,255)

  serial.write(outData);

  fill(255);

  textSize(30);

  text("incoming value: " + inData, 10, 30);

}

function serialEvent() {

  inData=serial.read();

}

function serialError(err) {

  console.log('Something went wrong with the serial port. ' + err);

}

​