Serial control of Arduino pins (not reading them, writing them) from Max

Mar 4, 2013 at 11:49am

Serial control of Arduino pins (not reading them, writing them) from Max

Hi all,

I’m having a bit of a brain teaser here, trying to sort out how to send PWM controls to multiple Arduino pins. As a start I thought I’d make a Max patcher to send the 3 pin control info and the ASCII n symbol to interface with this Arduino tutorial sketch using an RGB LED:

I’m having trouble figuring out how to follow the 3 data values with the ASCII n (line feed/newline) code. Any suggestions?

Thanks in advance!


Mar 5, 2013 at 8:51pm

Can you post your patch and arduino code ?

Mar 6, 2013 at 9:13am

Hi Nat,

Thanks for the reply. The Arduino code is in the link in the original post. I’ll attach it below, for convenience.

I’m wanting to send the 3 control data bytes from Max rather than from the Arduino IDE serial monitor, as the sketch is set up for (3 binary bytes (0-255) comma or space separated, followed by ASCII 10). My (unsuccessful) Max patch is pasted below. I have no trouble sending the binary bytes successfuly by themselves, but getting them to be followed by the ASCII new line is where I’m getting hung up. Also, I’m not too worried about sending/receiving the data back from Arduino to Max – that part will be discarded as soon as I get the patch working.



Max patch:

– Pasted Max Patch, click to expand. –

Arduino sketch:

Reading a serial ASCII-encoded string.

This sketch demonstrates the Serial parseInt() function.
It looks for an ASCII string of comma-separated values.
It parses them into ints, and uses those to fade an RGB LED.

Circuit: Common-anode RGB LED wired like so:
* Red cathode: digital pin 3
* Green cathode: digital pin 5
* blue cathode: digital pin 6
* anode: +5V

created 13 Apr 2012
by Tom Igoe

This example code is in the public domain.

// pins for the LEDs:
const int redPin = 3;
const int greenPin = 5;
const int bluePin = 6;

void setup() {
// initialize serial:
// make the pins outputs:
pinMode(redPin, OUTPUT);
pinMode(greenPin, OUTPUT);
pinMode(bluePin, OUTPUT);


void loop() {
// if there’s any serial available, read it:
while (Serial.available() > 0) {

// look for the next valid integer in the incoming serial stream:
int red = Serial.parseInt();
// do it again:
int green = Serial.parseInt();
// do it again:
int blue = Serial.parseInt();

// look for the newline. That’s the end of your
// sentence:
if ( == ‘n’) {
// constrain the values to 0 – 255 and invert
// if you’re using a common-cathode LED, just use “constrain(color, 0, 255);”
red = 255 – constrain(red, 0, 255);
green = 255 – constrain(green, 0, 255);
blue = 255 – constrain(blue, 0, 255);

// fade the red, green, and blue legs of the LED:
analogWrite(redPin, red);
analogWrite(greenPin, green);
analogWrite(bluePin, blue);

// print the three numbers in one string as hexadecimal:
Serial.print(red, HEX);
Serial.print(green, HEX);
Serial.println(blue, HEX);

Mar 6, 2013 at 10:08am

Clearly posting the Arduino code made a mess…it’s probably easier just to copy & paste from the link in the original post…

Mar 6, 2013 at 11:31am

I just realized I posted the wrong version of my Max patch…and In doing so, I think I’ve sorted out the issue – but I don’t have my Arduino here, so can’t test it until tomorrow. So, I’ll wait to resend the correct version of the patch until I’ve had a chance to try it out tomorrow.


Mar 7, 2013 at 1:42am

OK, just for completeness’ sake, here’s the correct and working version of the Max patch that interfaces with the Arduino sketch in the linked URL.

– Pasted Max Patch, click to expand. –
Mar 7, 2013 at 3:54am

DId you try with ascii character 13 (CR) ?
Sometimes it expects CRLF so 13 10

Mar 7, 2013 at 7:45am

This particular sketch only looks for 10, though you’re right, they often come together.

Mar 7, 2013 at 3:34pm

Hmmm, did you try sending messages individually (by using the iter object ?

Mar 8, 2013 at 12:39am

Hi Nat, actually, as I mentioned in the post where I attached the last version of the Max patch, everything is correct and working now. Sorry for the confusion – it’s all sorted out now. Thanks!

Nov 21, 2013 at 11:02pm

Thank you for posting your research!


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