Using MouseX in processing to control LEDs. Error in code - LEDs remain off I am fairly new to processing and Arduino - I have a coursework deadline for both on Monday (6th January). 

I am trying to write a script that uses the mouseX values to turn LEDs on and off. I haven't got any error messages on either of the scripts but currently, nothing happens to the LEDs (they remain off) when I move my mouse. I have tested the circuit with a simpler Arduino code and it is correct so there must be an error in my code!

I would be very grateful for some help. Thanks! 

Processing code:

import processing.serial.*;
Serial port;  
byte lightsOn;

void setup()
{
  size(600,300);
  port=new Serial(this,"/dev/cu.usbmodem1411",9600);
}

void draw()
{
  background(32,78,95);
  rect(300,0,300,300);
  noStroke();
  fill(185,215,216);

  lightsOn=byte(mouseX);
  port.write(lightsOn); 

  println(lightsOn);
}


Arduino code:

#include &lt;Servo.h&gt;

Servo myservo;
int ledpinA=12; 
int ledpinB=13;

void setup() 
{
  Serial.begin(9600);
  myservo.attach(ledpinA&amp;&amp;ledpinB);
  pinMode(ledpinA,OUTPUT);
  pinMode(ledpinB,OUTPUT);
}

void loop()
{
  if(0&lt;Serial.available())
  {
    int data = Serial.read();

  if (data&gt;300)
  {
    digitalWrite(ledpinA, HIGH);
    digitalWrite(ledpinB, LOW);
  }
  else
  {
    digitalWrite(ledpinB, HIGH);
    digitalWrite(ledpinA, LOW);
  }
  }
}
lightsOn=byte(mouseX);


A byte can be any number from -128 to 127 (Java has no concept of "unsigned" values). The Arduino will reinterpret that as a value from 0 to 255.

if (data&gt;300)


255, the maximum value, can never be more than 300 - so this will always fail.

You need to re-think what data you are sending and how you want to send it.