Member Avatar for fatalaccidents

Hello all,

This is a two parter. One is an error that I'm receiving and one is a question in general about the capabilities of PyUSB.

1) So I've installed libusb from the tar file by just doing ./configure && make && sudo make install and I have checked that the library is in my /usr/local/lib and that my LD_LIBRARY_PATH is looking there. Out of frustration I also did sudo port install libusb as well. In either case I'm receiving this error:

In [1]: import usb.core

In [2]: dev = usb.core.find(find_all=True)
---------------------------------------------------------------------------
ValueError                                Traceback (most recent call last)
<ipython-input-2-f185198e950d> in <module>()
----> 1 dev = usb.core.find(find_all=True)

/Users/matthewbray/Library/Enthought/Canopy_64bit/User/lib/python2.7/site-packages/usb/core.pyc in find(find_all, backend, custom_match, **args)
    854                 break
    855         else:
--> 856             raise ValueError('No backend available')
    857 
    858     k, v = args.keys(), args.values()

ValueError: No backend available

I'm not sure how to get it to see the backend and google isn't really helping me that much.

2) I'm looking to receive information from a thermometer that plugs in through USB (Fluke 568 IR thermometer) and was hoping that I could get the reading through some pyUSB interface. Is that even something that is possible? I was going to just play around with it and see if I could get anything, but I'm unable to even get anything to run as long as it can't find a backend.

Thanks for your time!

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Member Avatar for fatalaccidents

It might be pertinent to point out that I'm using Mac OSX Snow Leopard. Thanks!

Member Avatar for woooee

2nd hit on Google pyusb backend not accessible. You have to install an additional lib that pyusb depends on, and it's also on the pyusb site but the web site isn't real clear saying that you have to install one of the library dependencies. Please mark this as solved.

Edited by woooee
Member Avatar for fatalaccidents

I have libusb1.0 installed, but for some reason pyUSB doesn't seem to be able to find it. It seems like it is a Mac problem. I installed it on my Windows machine and it works just fine. I haven't had enough time to play with it to see if it actually has the capabilities I'm looking for though. I still can't get it to recognize any backend on the Mac side.

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