Re: [pyusb-users] unknown error in pyusb

[Debapratim G. <deb...@gm...>]

On Thu, Jul 12, 2012 at 2:11 AM, Tormod Volden <lis...@gm...>wrote:

> On Wed, Jul 11, 2012 at 8:03 PM, Debapratim Ghosh
> <deb...@gm...> wrote:
> > I am working with python in Ubuntu 11.10. I'm able to detect a USB
> device,
> > access its properties etc. Now I want to establish USB communication. As
> > given in the pyusb tutorial webpage, I gave a command
> >
> > pingu = usb.core.find(idVendor = 0x04D8, idProduct = 0xFEAA) #this is
> > working fine now, and then....
> >
> > pingu.set_configuration() #this gives the following error
> >
> > Traceback (most recent call last):
> >   File "testui1007.py", line 78, in startHandler
> >     pingu.set_configuration()
> >   File "/usr/local/lib/python2.7/
> > dist-packages/usb/core.py", line 547, in set_configuration
> >     self._ctx.managed_set_configuration(self, configuration)
> >   File "/usr/local/lib/python2.7/dist-packages/usb/core.py", line 92, in
> > managed_set_configuration
> >     self.backend.set_configuration(self.handle, cfg.bConfigurationValue)
> >   File "/usr/local/lib/python2.7/dist-packages/usb/backend/libusb10.py",
> > line 503, in set_configuration
> >     _check(_lib.libusb_set_configuration(dev_handle, config_value))
>
> I wonder what config_value is at this point. You can always add a
> little "print" in the above libusb10.py file to see. If the device was
> already configured and is reconfigured with the same value, it will
> typically perform a reset*. This might give an unknown error. Just a
> guess.
>
> Maybe you can give more information on the version of your pyusb and
> libusb-1.0, and even a lsusb -v dump of your device?
>
> Regards,
> Tormod
>

   Hi

   I used the function device.set_configuration(2).
   Also, I added a print statement to print the config_value in the part
you mentioned. It shows config_value = 2. However, the error is still
present. In the previous post, you can check that I did a lsusb -v dump of
my device. Is there an issue with libusb? How do I check if it is installed
on my linux os?

thanks.


>
>
> *) See http://libusb.sourceforge.net/api-1.0/caveats.html
>
> >   File "/usr/local/lib/python2.7/dist-packages/usb/backend/libusb10.py",
> > line 403, in _check
> >     raise USBError(_str_error[ret], ret, _libusb_errno[ret])
> > usb.core.USBError: [Errno None] Unknown error
> >
> > I am logged in as root, so authentication cannot be an issue right?
> >
> > Please give some idea why this is happening? I tried making a debug log
> > file, but the log file doesn't get created.
> >
> >
> > --
> > Regards,
> >
> > Debapratim Ghosh
> > IIT Bombay
>
>
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-- 
Regards,

Debapratim Ghosh
IIT Bombay