[PD] Pduino sysex vs. OSC advice

[Christof Ressi]

The CNMAT OSC library works well and I often used it with a serial connection. The documentation, however, is not so good and some of the examples are buggy. I attached some test sketches/patches I once made for a class presentation. The arduino sketch explains how to easily send and receive OSC messages via a serial connection (make sure you use the same baud rate on both sides!)

Although OSC is convenient, it can be a waste of ressources if you send lots of messages. I often work with raw SLIP packages instead, where the first byte is used for addressing and the other bytes are the actual data (using some bit shifting to break up integers into several bytes). In the arduino code, use SLIPSerial.read() to fill an array (instead of an OSC message) and interpret your data as needed.

You can also make your own simple protocol where you define a certain character to signify the start or end of a message. But how do you know if it's not part of the data? SLIP uses escape sequences to handle this case. Two alternative solutions:
a) work with fixed length messages and count bytes (not very safe)
b) reduce the range of possible values for your data (e.g. 0-127, like MIDI) and reserve the rest for addressing (128-255). If you need a greater resolution for your values, just break them up into several bytes. This way, sending a single 16 bit integer would take 4 bytes (address, bit 14-15, bit 13-7, bit 0-6). 

Christof

Gesendet: Mittwoch, 01. Juni 2016 um 17:16 Uhr
Von: "Martin Peach" <chakekatzil at gmail.com>
An: "pd-list at lists.iem.at" <pd-list at lists.iem.at>
Betreff: Re: [PD] Pduino sysex vs. OSC advice

There's an OSC library for Arduino here:
https://github.com/CNMAT/OSCUsing SLIP it can communicate over serial line using [comport] on the Pd end.
 Martin
 
On Wed, Jun 1, 2016 at 10:29 AM, Rick Snow <ricksnow at gmail.com[ricksnow at gmail.com]> wrote:

Hello list!
 
I am looking for some advice on sending messages from PD to an Arduino sketch.  Essentially, I plan to connect a mac to an Arduino via USB and control a large amount of variables within the Arduino sketch from PD.  
 
Is using the sysex message with the [arduino] object message the way to go with this?  How can I "tag" the messages so that they go to the correct variable in the arduino sketch?  Is there a practical limit to the speed of such a system?
 
I am much more familiar with using OSC messaging between applications but when I looked into using OSC with Arduino it seemed like I needed to use an ethernet shield (instead of connect via usb) and I would rather not go that route unless absolutely necessary.
 
Any advice is much appreciated!
 
cheers,
Rick 
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