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Re: Python, USB and cygwin

At 11:41 PM 12/15/2004, you wrote:

>I have a couple of USB devices which are based upon FTDI chips.  I am using
>the FTDI virtual serial port drivers.
>The devices appear to work properly except when attempting to communicate
>with them via cygwin python.  Scripts which work o.k. with Windows python
>will not work properly with cygwin python.  The point of failure depends
>upon the Windows version.
>Under Windows 98, the scripts fail to complete the opening of the virtual
>serial port,.  The failure occurs in tcgetattr and an error '22, Invalid
>argument' is returned.  I haven't followed this further into the bowels of
>python to work out what this means but tcgetattr() in cygwin 'C' does not
>Under Windows 2000, the same python scripts go further but fail further
>down the track, early during the attempted transfer of data.
>The same python scripts have worked well in the past under cygwin when I
>use a real serial port.
>Are there known problems with cygwin python and USB virtual serial ports?
>If so, are there any solutions or work-arounds?

There's nothing about your configuration that looks troublesome that I 
can see.  If things work well with real serial ports and Cygwin but not
with virtual serial ports, the problem may actually be with the virtual
serial port drivers.  But there's no way to really tell without 
investigating further.  If there are others on this list using the 
chips you are with the same problems with those virtual serial port drivers,
then they may have more information or be willing to track down this 
problem for you.  If not, you may be "stuck" trying to figure out
what's wrong on your own, more or less.  Since the problem isn't obvious
without the virtual serial port drivers, only those with them could track
this further. :-(

Larry Hall                    
RFK Partners, Inc.                      (508) 893-9779 - RFK Office
838 Washington Street                   (508) 893-9889 - FAX
Holliston, MA 01746                     

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