Re: [Libusb-win32-devel] libusb timeout and sync errors

[Dan E. <Dan...@ne...>]

Have you tried building from the top of cvs? There have been a number of
fixes since the last release.

Dan.

Ray Schumacher wrote:
> Hi all,
>=20
> We have been trying to use the libusb driver to bulk_read from the Ti
> ads1271 via the pyusb http://pyusb.berlios.de/ wrapper for Python.=20
> The problem is that there is some bulkread() miscommunication between
> the Python app and the Ti USB (implemented in firmware on the MMB0).
> I have not gotten the Ti data to be collected fault-free via the
> (required) bulk_read() method after many hours of testing various
> settings and timings.   =20
> The Labview demo (using the Labview usb DLL, I assume) has no issues
> at any speed or settings.=20
>=20
> I was testing using a 10Hz wave and data rates from 23Ksps to 55Ksps.
> At low data rates the most compact Python code for bulkRead'ing could
> read megasamples with few errors, but, the data is inevitably,
> silently, corrupted.  =20
>=20
> Requiring windows to update the DOS window (giving it focus) has
> horrible effects on performance of the USB interaction, with loads of
> reap_async timeout errors as well as silent corruption/data dropping;
> the data result can also be missing data in the absence of a thrown
> error. The latter is typical of the wx GUI app I did. The GUI program
> suffers the same problem, where a GUI with a DOS window is worst. It
> is evident that libusb/Python falls behind the
> expectation/requirements of the firmware as something on the PC is
> interrupted, and the Ti USB just quietly sends it the next data it
> has.       =20
>=20
> I also tried using ctypes
> http://starship.python.net/crew/theller/ctypes/
> to call the win32 libusb0.dll directly and bypass the pyusb wrapper,
> but failed to properly construct a device handle/pointer and didn't
> try more in that direction. The C code I was following was from the
> win32 package:  =20
>
http://libusb-win32.cvs.sourceforge.net/*checkout*/libusb-win32/libusb/t
ests/testlibusb_win.c
>=20
> If libusb only worked for me on LINUX, that would be fine also -
> there are some notable USB implementation differences with Win32,
> which I don't fully understand. One of them, usb_reap_async(), is
> what time-out errors often in my programs. (It appears to be waiting
> when it errors
>
http://msdn.microsoft.com/library/default.asp?url=3D/library/en-us/dllpro=
c
/base/waitforsingleobject.asp
> but I can't see what ever calls it directly, not even bulk_read(), or
> why.)=20
>=20
> System is an AMD Opteron, Python 2.4, libusb 0.1.10.1
>=20
> Thanks for any insight,
> Ray
>=20
>=20
>
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