LibUSB crash while Logitech Camera is plugged in

[PtubbyTaylor]

My code works wonderfully while the NXT is the only thing connected, but if I have my webcam plugged in while it starts up, it does this:

Traceback (most recent call last):

  File "server.py", line 14, in <module>

    nxt = nxt.locator.find_one_brick() #"00:16:53:0A:BE:39"

  File "C:\Python27\lib\site-packages\nxt\locator.py", line 112, in find_one_bri

ck

    for s in find_bricks(host, name, silent, method):

  File "C:\Python27\lib\site-packages\nxt\locator.py", line 43, in find_bricks

    for s in socks:

  File "C:\Python27\lib\site-packages\nxt\usbsock.py", line 84, in find_bricks

    for bus in usb.busses():

  File "C:\Python27\lib\site-packages\usb\legacy.py", line 333, in busses

    return (Bus(),)

  File "C:\Python27\lib\site-packages\usb\legacy.py", line 329, in __init__

    self.devices = [Device(d) for d in core.find(find_all=True)]

  File "C:\Python27\lib\site-packages\usb\legacy.py", line 314, in __init__

    self.configurations = [Configuration(c) for c in dev]

  File "C:\Python27\lib\site-packages\usb\core.py", line 723, in __iter__

    yield Configuration(self, i)

  File "C:\Python27\lib\site-packages\usb\core.py", line 419, in __init__

    configuration

  File "C:\Python27\lib\site-packages\usb\backend\libusb01.py", line 408, in get

_configuration_descriptor

    return dev.config[config]

ValueError: NULL pointer access

[Marcus Wanner]

This looks like a pyusb/libusb issue which may be a result of the
webcam not behaving as expected (most likely in violation of some kind
of spec). Run this with and without the webcam plugged in:

import usb
for bus in usb.busses():
for device in bus.devices:
pass

And see if you get the same thing.

--
Marcus Wanner

[Philip T]

crashes while plugged in, outputs nothing while unplugged

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[Marcus Wanner]

On Wed, May 01, 2013 at 02:20:46PM -0400, Philip T wrote:
> crashes while plugged in, outputs nothing while unplugged

Awesome, that means it's not an nxt-python problem. Please report to
the pyusb folks. Thanks!

--
Marcus Wanner

[Philip T]

I updated libUSB and the problem went away. Now I can (hopefully) live-stream my NXT on the webpage where I've set up controls for it.

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