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

[RayS <ra...@bl...>]

At 02:04 AM 8/25/2006, Dan Ellis wrote:
>Have you tried building from the top of cvs? There have been a 
>number of fixes since the last release.

Hi Dan,

No, I have not. But, Wander Lairsan said he was about to release a .4 
pyusb version with all new build - I'll check on how he's doing.

Thanks,
Ray

Ray Schumacher wrote:
 > Hi all,
 >
 > 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.
 > 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.
 > The Labview demo (using the Labview usb DLL, I assume) has no issues
 > at any speed or settings.
 >
 > 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.
 >
 > 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.
 >
 > 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:
 >
http://libusb-win32.cvs.sourceforge.net/*checkout*/libusb-win32/libusb/t
ests/testlibusb_win.c
 >
 > 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=/library/en-us/dllproc
/base/waitforsingleobject.asp
 > but I can't see what ever calls it directly, not even bulk_read(), or
 > why.)
 >
 > System is an AMD Opteron, Python 2.4, libusb 0.1.10.1
 >
 > Thanks for any insight,
 > Ray
 >
 >&