I'm running Mac OS X 10.8 with python 2.7. I installed libusb with MacPorts and it does work (tested my importing usb.core & usb.util). However, each time I try to access a device, I get the following error:
>>> dev=usb.core.find(idVendor=0x1d50, idProduct=0x6048)
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "/Library/Python/2.7/site-packages/usb/core.py", line 829, in find
raise ValueError('No backend available')
ValueError: No backend available
I've tried several other things, like import usb.backend, yet I wasn't sure what that was supposed to do. Same result, after 3 days of working on it.
Thanks for any help in advance!
EDIT: This has actually changed. I'm not sure which file I modified and how, but now the following works:
>>> import usb
>>> usb.core.find(idVendor=0x1d50, idProduct=0x6048)
<usb.core.Device object at 0x10eb2f2d0>
However, now when I run sudo rfcat -r (which is the real purpose of getting libusb working), I still get these error messages:
Error in resetup():ValueError('No backend available',)
EDIT: It seems that the issue is with ipython. When I start ipython as root and import usb, I'm not able to find my device:
In [1]: import usb
In [2]: import usb.util
In [3]: import usb.core
In [4]: usb.core.find(idVendor=0x1d50, idProduct=0x6048)
---------------------------------------------------------------------------
ValueError Traceback (most recent call last)
<ipython-input-4-7884198c46c2> in <module>()
----> 1 usb.core.find(idVendor=0x1d50, idProduct=0x6048)
/Library/Python/2.7/site-packages/usb/core.pyc in find(find_all, backend, custom_match, **args)
827 break
828 else:
--> 829 raise ValueError('No backend available')
830
831 k, v = args.keys(), args.values()
ValueError: No backend available
In [5]:
EDIT: Jesis christ, once again. If I start python, then run the following:
>>> from IPython.frontend.terminal.ipapp import launch_new_instance
>>> launch_new_instance()
I get an ipython prompt. When in it I import usb and find my device, there isn't a backend error.
If I import usb in python, then do those commands above to get an ipython prompt, and then find my device, I get a "name 'usb' not defined" error. Then, I import usb and find my device, then there's no error.
At this point, I'm extremely confused. The commands above are exactly what /usr/local/bin/ipython contains, so I should be getting identical results.
I've gotten this fixed. Apparently, both rfcat and ipython binaries pointed to the wrong binaries of python - not /opt/local/bin/python. Changed that in vim, and it all runs fine.
Now, the issue is that libusb can't seem to get a good hold of the device - it can't do the most basic commands, but that's for another question.