Forums > MaxMSP

serial command to projector as one BYTE (keyspan USA-19QW)

February 21, 2010 | 5:51 pm


I know this isn’t the most popular thing to do these days, but I am attempting to control a device through serial commands. I’ve done it before, but this time Im a little stumped.

I need to send the following (according to panasonic manual and tech support there)

STX as one byte – but of course when I use atoi / spell in conjunction with the serial object, it sends 3 bytes.

What am i missing here to be able to send a string as a single byte?

I would really appreciate some help on this one…

Im using a mac mini, OS 10.5, max5 + keyspan USA-19QW USB->serial adapter

thanks in advance

February 21, 2010 | 7:03 pm

STX must be a nemonic for some byte, no? An ASCII character is 7 or 8 bits, depending on your definition, so "STX" could never be sent as one byte as ASCII.

Is there a link to the manual for the projector?

February 22, 2010 | 4:13 pm

here’s a link for the serial protocol:

Sadly, panasonic tech support has told me they won’t help me, as they do not support usb-> serial converters. strange, but I think I may call them and pretend to be someone else. though if you have a clue, it would be a help.

Ive tried with a nullmodem cable, a pass through cable, and just nada, nothing doing, so I am guessing it has to do with this STX ‘command’ ETX string.


February 22, 2010 | 5:04 pm

I’ve seen this before where the commands were sent in hex
STX = 02
ETX = 03


February 22, 2010 | 6:58 pm

Turns out STX and ETX are ASCII control chars:
STX == 02
ETX == 03

February 22, 2010 | 10:03 pm

Wow, this is a great resource – I was a little lost here. One last question and I can link this all together, how do i send hex numbers out the serial object?

thanks for your help guys…


February 23, 2010 | 4:44 am

As an update to the above – I’ve tried everything I can figure out, but of course sending anything through the serial gets converted to an integer there. So sending a ‘2’ actually results in ’50’ – spell, atoi and so on don’t cut the mustard.

so how to send hex out the serial port then?

February 23, 2010 | 11:10 am

I’ve done a projector remote to switch on and off the projector with serial commands. It uses an arduino only. You can find details (in french) at
and code at

Hope it helps.

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