Send Color value from Processing into Arduino

Question

I know this has been asked before, but I'm new to Arduino and Processing, and I'm trying to take this step by step.

I would like to pass an RGB value from processing, into Arduino via the Serial.Write/Read.

I have my Processing as:

void draw(){
 //orange colour in RGB values
 color _rgbColor = color(255, 40, 0);
 //convert colour into hex
 String _hexColor = hex(_rgbColor, 6);
 //convert colour into binary
 String _binaryColor = binary(_rgbColor);
 //pass colour to port
 myPort.write(_hexColor);
 delay(500);
}

I assume I can just pass the HEX value straight across, right?

First problem I get is that I can't debug what my Arduino device is getting (when I run the Processing program, the Serial Monitor wont work. Seems like I can only use one or the other). I can print the myPort.read within my Processing after the delay, and I get:

-1

So I'm not quite sure what I'm doing wrong there.

On the Arduino side, I'm using Serial.read() to retrieve the Serial data, which I assume will all be broken down into bytes, so I need to then convert it into a HEX formate, right?

----- Update -----

I now know that I need to break down my color variable into a char-message. I'm guessing I can do something like this then, for example: And then on the other side (Arduino), I need to rebuild the message, right?

if(mousePressed == true){
 //Red
 myPort.write('2'); 
 myPort.write('5'); 
 myPort.write('5');
 myPort.write(','); 
 //Green
 myPort.write('0'); 
 myPort.write('3'); 
 myPort.write('0');
 myPort.write(','); 
 //Blue
 myPort.write('0'); 
 myPort.write('0'); 
 myPort.write('0');
 myPort.write('\n'); 
 }

My Arduino script is as follows, is this an okay route to go down?

String message;
void loop() {
 int _size = Serial.available();
 if(_size > 0){
 char value = Serial.read();
 message += value;
 //full message received (255,255,255)
 if(message.length() == 11){
 String _red = message.substring(0,3);
 String _green = message.substring(4,7);
 String _blue = message.substring(8,11);
 Serial.println("R:" + _red + " G:" + _green + " B:" + _blue);
 //apply to light system
 setColour(_red.toInt(), _green.toInt(), _blue.toInt());
 //clear buffer
 message = "";
 Serial.flush();
 }
 }
}

• Majenko: You should digest this first: hackingmajenkoblog.wordpress.com/2016/02/01/…
• Majenko: Also you should understand exactly how the UART protocol (RS-232) works.
• Oliver Jones: Surely someone, somewhere has already made a defined script for this? To simply pass a colour variable to the Serial?
• Majenko: Many people have, yes. It is a simple enough operation once you understand how a UART works that it becomes a non-entity and you don't need to really worry about finding special code for it.
• Majenko: The simplest way is to print the three colour values as a comma-separated line, maybe with a prefix character to indicate the start (C23,49,119\n for example). Then it is a case of reading that string and interpreting it properly.

Answer 1

Add print(_hexColor); to you processing sketch. The value it's sending should appear in the Processing Console (at the bottom)

Answer 2

I know I'm late, but actually got a working solution, when I was working out a solution for this.

Code in Processing assuming variable myPort is handled in setup():

void draw() {
 int r = 255;
 int g = 123;
 int b = 2;
 myPort.write('S'); // tell the arduino to do something with leds
 myPort.write(r);
 myPort.write(g);
 myPort.write(b);
}

Code for Arduino loop:

void loop() {
 int r;
 int g;
 int b;
 if(Serial.available()) { 
 if(Serial.read() == 'S') {
 while(!Serial.available()){}
 r = Serial.read();
 while(!Serial.available()){}
 g = Serial.read();
 while(!Serial.available()){}
 b = Serial.read();
 }
 delay(10); // some recovery time, not sure if nessecary
 // do something with rgb values
 }
}

This works for me with every possible RGB range. It's not the most elegant solution, but by far better then converting between strings/chars and ints with different bit counts on different devices.

• gre_gor: 002 is an octal number. In this case it's still 2, but 020 would be 16. Don't use leading zeros, unless you actually want octal numbers.
• Cronay: you're right, I wrote this on the fly!