Dear fellow pd-ers,
I'm using comport to communicate with arduino/teensy for quite long time now, and I didn't encounter any serious issues while using one or two comport objects (and respectively one or two arduinos/teensies). But when I'm trying to connect three at a time, there are some problems, both when when connecting directly to computer's usb ports, and when using powered usb hub. I tried on two different computers. I'm getting this kind of messages in the console:

[comport]: WriteFile:GetOverlappedResult error: 31
[comport] ** ERROR ** couldn't reset params to DCB of device COM42
One of the teensies doesn't react, sometimes Pd freezes and unfreezes only when I disconnect the teensy in question.

Is there some hard limit in Pd - that you can't use more than two comports at once? Teensies are not draining that much power from usb, thei're controlling motor boards that have external power.

Any ideas?

EDIT: I'm using latest available version of PD-Etended

P.S. maybe there's some better alternative to comport in recent versions of Vanilla (wfich I'm not familiar with)?

Pd-vanilla has no [comport] equivalent, so you'll have to go with that. Why still use extended which is no longer supported? Did you try using three [comport]s with vanilla?
If you still get the same problem then maybe you'll need to have the additional Teensys work as slaves to one of the two Teensys connected to your computer and send data via SPI.

Thanks for reply!
I tried Pd Vanilla, unfortunately it's the same situation. Will probably have to control the other teensy as slave via i2c or something, as you suggested...

update: I eventually managed to daisy-chain two teensys via uart, and to forward data from pd thru teensy 1 to teensy 2, hopefully it will work also with third teensy. If anyone needs info on how this could be done, I could post the patch and code.