Skip to content

RGB Mixer – Processing to Arduino

It has been a long time since I wanted to control the arduino with processing and I tried a lot of libraries, and a lot of processes and I always felt that none of those were suited for what I needed. I needed something simple to implement and easy to understand, and because I am not a programmer, I asked for help and @pauloricca replied to me with a quick, fast and really good solution.

In this example I have connected an RGB LED to the Arduino and on Processing we will have a simple mixer to fade in and out color channels. DON’T DO THIS, LED’s always need to have one resistor in series before. In this case I just wanted to show the serial communication part, and I skipped the resistor part, lazy me! Never do this, otherwise you will kill your leds very fast.

RGB Mixer - Processing to Arduino

On the Arduino side, I defined 3 digital output pins 9, 10, 11, these are PWM capable pins. Than I defined pin 8 as an OUTPUT, and digitallyWrite it to LOW, to be the GROUND pin. On the loop() function we used a switch() function that detects when the sync characters ’R’, ‘G’ and ‘B’ are received. These characters will tell us what value is coming next. The function GetFromSerial() is called everytime we need to read a value from the serial port.

void setup()
  // declare the serial comm at 9600 baud rate

  // output pins
  pinMode(9, OUTPUT); // red
  pinMode(10, OUTPUT); // green
  pinMode(11, OUTPUT); // blue

  // another output pin o be used as GROUND 
  pinMode(8, OUTPUT); // ground
  digitalWrite(8, LOW);

void loop()
  // call the returned value from GetFromSerial() function
  case 'R':
    analogWrite(9, GetFromSerial());
  case 'G':
    analogWrite(11, GetFromSerial());
  case 'B':
    analogWrite(10, GetFromSerial());


// read the serial port
int GetFromSerial()
  while (Serial.available()<=0) {

On the Processing side, I am using a slider class adapted from, and I created 3 instances of this class (I assume you understand the concept of class). The important thing to understand here is the import of the Serial library, and the creation of a Serial object called “port”. On the setup() function I print out the available serial ports and than I defined which one is the Arduino port, on my case is the number 0, note that I am using mac, if you are using PC it should be COM1, COM2 or another COM#. Finally I am passing the values of the slider after I pass the sync character ‘R’, ‘G’, ‘B’.

RGB Mixer - Processing to Arduino

import processing.serial.*;
Serial port;

sliderV sV1, sV2, sV3;

color cor;

void setup() {
  size(500, 500);

  println("Available serial ports:");

  // check on the output monitor wich port is available on your machine
  port = new Serial(this, Serial.list()[0], 9600);

  // create 3 instances of the sliderV class
  sV1 = new sliderV(100, 100, 90, 255, #FF0000);
  sV2 = new sliderV(200, 100, 90, 255, #03FF00);
  sV3 = new sliderV(300, 100, 90, 255, #009BFF);

void draw() {


  // send sync character
  // send the desired value

Slider Class -
based on slider class
class sliderV {
  int x, y, w, h, p;
  color cor;
  boolean slide;

  sliderV (int _x, int _y, int _w, int _h, color _cor) {
    x = _x;
    y = _y;
    w = _w;
    h = _h;
    p = 90;
    cor = _cor;
    slide = true;

  void render() {
    rect(x-1, y-4, w, h+10);
    rect(x, h-p+y-5, w-2, 13);
    text(p, x+2, h-p+y+6);

    if (slide==true && mousePressed==true && mouseX<x+w && mouseX>x){
     if ((mouseY<=y+h+150) && (mouseY>=y-150)) {
        p = h-(mouseY-y);
        if (p<0) {
        else if (p>h) {

RGB Mixer - Processing to Arduino

RGB Mixer - Processing to Arduino

RGB Mixer - Processing to Arduino


{ 9 } Comments

  1. davide | August 5, 2010 at 10:05 am | Permalink

    hi guilherme!

    why not using the Arduino Library for Processing?
    Everything moves to the Processing IDE.


  2. GUI | August 7, 2010 at 11:12 am | Permalink

    I remember I tried that library once, but I didn’t worked, maybe I missed something at the time, must try it again.
    Thank you for your comment.

  3. André Delgado | September 4, 2010 at 6:21 pm | Permalink

    I like the sliders (: cute

  4. singul4r1ty | July 13, 2011 at 5:57 pm | Permalink

    Great code – I’ve been trying to get this to work for ages. I have my iPod touch controlling the 3 colors over OSC, and this code had the way I needed of sending over the 3 values. Thanks very much!

  5. GUI | July 13, 2011 at 9:53 pm | Permalink

    Hey! It so cool to know it helped you out!! Thanks for letting me know!

  6. Fábio Santos | August 20, 2011 at 2:26 am | Permalink

    Boas, entendo o conceito deste projecto e queria tambem tentar fazer algo do genero para controlar umas fitas rgb..
    Agora o problema é que ainda tou muiito fraquinho na programação, não conheço certas funções e afins, mas decidi arranjar um arduino para ir treinando.
    Gostava se possível que me explicassem as etapas de todo este processo..


  7. GUI | August 21, 2011 at 8:57 pm | Permalink

    Olá, que etapas precisas ao certo de perceber? O melhor para começar no Arduino/Processing é seguir os vários exemplos existentes, posso-te aconselhar estes:
    Força com isso ;)

  8. Neurotek | August 8, 2013 at 5:52 pm | Permalink

    Hey !

    You made a mistake in your arduino code =/

    Case G must analog write on pin 10 and Case B on pin 11 =)

  9. GUI | August 14, 2013 at 9:28 am | Permalink

    True!! Thanks friend :)

Post a Comment

Your email is never published nor shared. Required fields are marked *