Messenger library

Messenger is a new library for Arduino. It is a “toolkit” that facilitates the processing of ASCII messages. Messenger processes characters until it receives a carriage return (CR). It then considers the message complete and available. The message is split into many elements as defined by a separator. The default separator is the space character, but can be any character other than NULL, LF or CR.

Messenger is the new SimpleMessageSystem. SimpleMessageSystem was nice, but not simple enough, so I wanted to switch to Firmata, but when I found out Firmata took at least half of my atmega168’s memory, I went back to the drawing board and designed Messenger.

Please note that Messenger only provides methods for incoming messages. The internal Serial.print() functions work just fine for outgoing messages.

You can find Messenger here.

Hey, thanks!

Can't wait to take it out for spin...

This will be very useful! I would love to use this with my new ethernet shield to parse caller ID messages and perhaps scrape web pages but, unfortunately, it doesn't support strings yet.

I would take this on myself but efficient string handling requires more C expertise than I have!

Any hope that string support will be added to the messenger library anytime soon?

The problem with strings is that they use up a big chunk of memory (1 byte per letter).

I could probably add string support. Something like: compareString(String) that would return a true or false. If the result is false, it stays in the buffer, if the result is true, it would pass to the next element of the message.

p.s.: I am not sure I posted the link before, but Messenger can be found here:

Yes, strings are memory hogs and are not easily handled in the Arduino environment. But something like Messenger could sure open a lot of interfacing possibilities!

I'd love to see support that allowed me to pick a string out of a sequence by position perhaps like:

readStr(index) returns the element at the index as a string (defined by the message separator).

Thanks for all you work on this so far!



Is it possible to use this library also on Serial1, Serial2 etc. available on the Arduino Mega? (This would be great)

Thank you

Is it possible to use this library also on Serial1, Serial2 etc.

Yes. You simply feed byte process(int serialData) with the serial data of the port you wish to parse. Please note that will also need one instance of the Messenger class for every port.

Hi, Thank you for indicating what needs to be done - I will answer back if this worked for me Ralph

I see what you mean - this was really not a too clever question of mine...

Thank you for providing this very useful library!


Could you develop the advantage of your solution compared with the bitlash one ?
Bitlash runs on 168 and allows one to dial with serial term as easily as :

i=3; while i<=8: pinMode(i,1); digitalWrite(i,1); i++

It allows the macro too.


Could you develop the advantage of your solution compared with the bitlash one ?

Well it is not a shoving match against messenger and bitlash that’s for sure! If you read the start of the thread, you will see I was looking for a light weight communication solution. Bitlash is not lightweight (takes up almost all the memory on a tamega168) and is not a simple communication protocol but a complete shell. Messenger is lightweight and very simple to implement.

Two string handling functions have been added to Messenger. Check them out here:


Excellent library I must say. Thanks for it. I am having some troubles trying to use Serial1 on the Arduino Mega. I basically took the example that is provided and changed Serial to Serial1. Can anyone take a look at my code below and help me please?

#include <Messenger.h>
// Instantiate Messenger object with the default separator (the space character)
Messenger message = Messenger(); 

// Create the callback function
void messageReady() {
    int pin = 10;
       // Loop through all the available elements of the message
       while ( message.available() ) {
      // Set the pin as determined by the message
         digitalWrite( pin, message.readInt() );

void setup() {
  // Initiate Serial Communication
  // Attach the callback function to the Messenger

void loop() {
  // The following line is the most effective way of using Serial and Messenger's callback
  while ( Serial1.available() )  message.process( () );

I can only help you if you describe what are the troubles you are experiencing.

oops sorry I should have explained.. Well really it just doesn't work. when i used the default Serial it did light up the LED on pin 13 upon entering the following text "1 1 1 1 1 1 1 1 1 1 1 1 1" followed by Enter. However as soon as i switch the Serial to Serial1. nothing happens. I can enter a million "1 1 1" followed by enter but the LED does not light up. I hope i have explained myself well. if you need any further details please do let me know

Thanks Swalehm

Well, the way you set up your code, Messenger processes messages comming in through Serial1. You therefore have to send the messages to Serial1 instead of Serial. What external circuitry are you using to do so?

When i change my code to serial then it uses the on board FTDI chip and it works. however on the other port i have a MAX233 chip which works fine because when I run the monitor I can see what the Arduino Mega is sending out(Serial.println). it just doesn't seem to pick up what I send to it through the serial monitor

I appreciate your assistance.

I am sorry, I still do not understand your configuration.
The Arduino Mega is plugged into your computer’s USB (that is Serial).
You have a MAX233 plugged into RX1, TX1 (Serial1). So you generate RS-232 level communication with the chip and that is plugged where? What is connected on the other side of the MAX233?

MAX233 chip which works fine because when I run the monitor I can see what the Arduino Mega is sending out(Serial.println)

Which monitor? The Arduino IDE’s? Doesn’t it only work with RX,TX and Serial? Do you mean you are echoing something like:


So how are you sending data to Serial1?

The second serial port is connected to the Serial port of a Computer. and I am running tera term pro(as a serial monitor). eventually I would like to have Processing( send out stuff to the Arduino but that would be at a later stage. so for now I have connected Serial1 to the computer via a MAX233 chip. My apologies for not explaining myself well.