# What dependencies do I need for USB programing in python with pyUSB?

I am trying to get the usb.find command to work properly in a python script I'm writing on Angstrom for the Beagleboard.

Here is my code:

#!/usr/bin/env python

import usb.core
import usb.util
import usb.backend.libusb01 as libusb

PYUSB_DEBUG_LEVEL = 'debug'
# find our device
# Bus 002 Device 006: ID 1208:0815
#  idVendor           0x1208
#  idProduct          0x0815
# dev = usb.core.find(idVendor=0xfffe, idProduct=0x0001)
# iManufacturer           1 TOROBOT.com

dev = usb.core.find(idVendor=0x1208, idProduct=0x0815,
backend=libusb.get_backend() )


I don't know what's missing, but here is what I do know. When I don't specify the backend, no backend is found. When I do specify the backend usb.backend.libusb01 I get the following error:

root@beagleboard:~/servo# ./pyServo.py
Traceback (most recent call last):
File "./pyServo.py", line 17, in <module>
dev = usb.core.find(idVendor=0x1208, idProduct=0x0815, backend=libusb.get_backend() )
File "/usr/lib/python2.6/site-packages/usb/core.py", line 854, in find
return _interop._next(device_iter(k, v))
File "/usr/lib/python2.6/site-packages/usb/_interop.py", line 60, in _next
return next(iter)
File "/usr/lib/python2.6/site-packages/usb/core.py", line 821, in device_iter
for dev in backend.enumerate_devices():
File "/usr/lib/python2.6/site-packages/usb/backend/libusb01.py", line 390, in enumerate_devices
_check(_lib.usb_find_busses())
File "/usr/lib/python2.6/ctypes/__init__.py", line 366, in __getattr__
func = self.__getitem__(name)
File "/usr/lib/python2.6/ctypes/__init__.py", line 371, in __getitem__
func = self._FuncPtr((name_or_ordinal, self))
AttributeError: python: undefined symbol: usb_find_busses


What am I missing so that this will work properly?

Thank you.

• It looks like you could be missing the libusb library, or have the wrong version installed somehow; the error doesn't seem to be coming from the python side.
– Ian
Dec 9 '13 at 2:52
• Libusb is installed and everything that I knew to install has been done so with OPKG package manager. That includes python-core, python-pyusb, python-ctypes, python-setup. Dec 9 '13 at 13:23
• @ChronoFish, if you have happened to discover the solution, please provide it as an answer to this question (and accept it too). Dec 9 '14 at 17:42
• @Shahbaz, I did not find a solution for this specific problem. I found a work-a-round: The device I was trying to interface responded to a generic arduino driver so my needs were met... Dec 10 '14 at 23:16