[PD] Comport and UBW problems on Linux

Thomas O Fredericks tof at danslchamp.org
Thu Oct 11 03:54:49 CEST 2007


I am creating an abstraction to ease the communication with an UBW (USB Bit
Wacker: http://greta.dhs.org/UBW/index.html).

The abstraction uses comport to communicate with the device. It is
considered as USB modem by the system. See the tail of dmesg when the device
is plugged in to my Ubuntu machine:

[102406.169656] usb 1-5: new full speed USB device using ohci_hcd and
address 8
[102406.381592] usb 1-5: configuration #1 chosen from 1 choice
[102415.654264] usb 1-5: USB disconnect, address 8
[102416.484598 ] usb 1-5: new full speed USB device using ohci_hcd and
address 9
[102416.706005] usb 1-5: configuration #1 chosen from 1 choice
[102416.708971] drivers/usb/class/cdc-acm.c: This device cannot do calls on
its own. It is no modem.
[102416.708984] cdc_acm 1-5:1.0: ttyACM0: USB ACM device

The problem is as follows:  The abstraction works fine in XP,
but in Ubuntu,
when I want to send more than three values
(i.e. something like [77,65,49,42,13< ),
comport complains that:

"[comport] write returned -1, errno is 11
Write error, maybe TX-OVERRUNS on serial line"

Now, ttyACM0 is a weird device because it does not have a baud rate. It
simply sends the data as fast as it can. So, this message DOES not make any
sense.

I know it is not a problem with my configuration of Ubuntu because I was
able to establish proper communication with Perl.

Anybody have a clue on how to solve this or modify comport? (I used a
version I compiled from pd cvs and another from pd-extended and both
failed).

Tom
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