No backend available python usb

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No backend available #26

No backend available #26

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Hi,
I am getting the error «No Backend Available»

When I set PYUSB_DEBUG_LEVEL=debug
I get the following error.

Traceback (most recent call last):

Fi_lib = _load_library()/site-packages/usb/backend/libusb10.py», line 648, in$

Firaise OSError(‘USB library could not be found’)d/libusb10.py», line 205, in$

OSError: USB library could not be found

I have both libusb1.0 and libusb0.4 installed. I have tried setting the LD_LIBRARY_PATH=/usr/lib but this is unsuccessful.

This is returned when I call the find function usb.core.find().

I’m using a linux OS. arm926 architecture

The text was updated successfully, but these errors were encountered:

I just saw you are using an old PyUSB version, please update PyUSB and check if you still have problems.

I will try and get back to you. thanks

I have to reanimate this thread. I have the same problem using python3.2.5, pyusb1.0.0b1 and libusb-win32 1.2.6.0 together with Windows 8.1. (I have no other windows installation to test it)

The libusb0.dll is present in C:\Windows\System32 and this path is listed in the PATH-enviroment variable of my cygwin shell.

$ python3 usbtest.py Traceback (most recent call last): File "usbtest.py", line 9, in dev = usb.core.find(find_all=True, idVendor=0x16c0, idProduct=0x05dc) File "/usr/lib/python3.2/site-packages/pyusb-1.0.0b1-py3.2.egg/usb/core.py", line 864, in find ValueError: No backend available 

Please, do a ‘set PYUSB_DEBUG=debug’ on the command line to define the PYUSB_DEBUG environment variable and post the output.

Hi,
Here is the output from using latest release;

2013-11-29 08:04:38,324 ERROR:usb.backend.libusb1:Error loading libusb 1.0 backend Traceback (most recent call last): File "/usr/lib/python2.7/site-packages/usb/backend/libusb1.py", line 896, in get_backend _lib = _load_library() File "/usr/lib/python2.7/site-packages/usb/backend/libusb1.py", line 293, in _load_library raise OSError('USB library could not be found') OSError: USB library could not be found 2013-11-29 08:04:38,397 ERROR:usb.backend.openusb:Error loading OpenUSB backend Traceback (most recent call last): File "/usr/lib/python2.7/site-packages/usb/backend/openusb.py", line 715, in get_backend _lib = _load_library() File "/usr/lib/python2.7/site-packages/usb/backend/openusb.py", line 256, in _load_library raise OSError('USB library could not be found') OSError: USB library could not be found 2013-11-29 08:04:38,553 ERROR:usb.backend.libusb0:Error loading libusb 0.1 backend Traceback (most recent call last): File "/usr/lib/python2.7/site-packages/usb/backend/libusb0.py", line 585, in get_backend _setup_prototypes(_lib) File "/usr/lib/python2.7/site-packages/usb/backend/libusb0.py", line 213, in _setup_prototypes lib.usb_open.argtypes = [POINTER(_usb_device)] File "/usr/lib/python2.7/ctypes/__init__.py", line 378, in __getattr__ File "/usr/lib/python2.7/ctypes/__init__.py", line 383, in __getitem__ AttributeError: Unable to resolve symbol Traceback (most recent call last): File "", line 1, in File "/usr/lib/python2.7/site-packages/usb/core.py", line 864, in find raise ValueError('No backend available') ValueError: No backend available

From logs, it cannot locate the libusb 1.0 shared library and there is a problem trying to load a symbol from libusb0 backend.

I recently merged the pull request #29 which allows you to manually specify the location of your library. Could you please give it a try to load the libusb 1.0 shared library?

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No backend available #120

No backend available #120

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Hello,when I use pyusb.It occured a error.I don’t know how to solve it.
All the error :
dev = usb.core.find(idVendor=0x0416,idProduct=0x5011)
File «/usr/lib/python2.7/site-packages/usb/core.py», line 1199, in find
raise ValueError(‘No backend available’)
ValueError:No backend available

The text was updated successfully, but these errors were encountered:

Getting this when trying to use it on a Synology DiskStation. Somehow there ctypes.util.find_library returns None for anything.

I would also like to bump this issue.

Is there any easy way to specify/hardcode where libraries are lying, instead of relying on the mechanisms to locate them?

Apologizes for the long delay, I am treating a disease and had to dedicate my free time to recovery. I just pushed a FAQ which intends to address common issues. It is a WIP doc.

The documentation is not very clear on this.

Remember that you need libusb (1.0 or 0.1) or OpenUSB running on your system. For Windows users, libusb 0.1 is provided through libusb-win32 package. Check the libusb website for updates (http://www.libusb.org).

But how and where do we install it? libusb-win32 is just a zip file. Lots of people having trouble with this:

I install it on openwrt system.A linux system.I will try to update my libusb.Thank you.

发自网易邮箱大师
在2016年01月12日 23:11，endolith 写道:

The documentation is not very clear on this.

Remember that you need libusb (1.0 or 0.1) or OpenUSB running on your system. For Windows users, libusb 0.1 is provided through libusb-win32 package. Check the libusb website for updates (http://www.libusb.org).

But how and where do we install it? libusb-win32 is just a zip file. Lots of people having trouble with this:

Pyusb on windows — no backend available
Pyusb on windows 8.1 — no backend available — how to install libusb?
libusb installed- but pyUSB backend not found
PyUSB ValueError: No backend available
PyUSB backend not accessible

—
Reply to this email directly or view it on GitHub.

all three backends are not working properly. How do you fix this error?

usb.core.find()
2016-01-12 22:02:52,362 ERROR:usb.libloader:Libusb 1 (/usr/local/lib/libusb-1.0.dylib) could not be loaded
Traceback (most recent call last):
File «/Library/Frameworks/Python.framework/Versions/3.4/lib/python3.4/site-packages/usb/libloader.py», line 116, in load_library
return ctypes.CDLL(lib)
File «/Library/Frameworks/Python.framework/Versions/3.4/lib/python3.4/ctypes/init.py», line 351, in init
self._handle = _dlopen(self._name, mode)
OSError: dlopen(/usr/local/lib/libusb-1.0.dylib, 6): no suitable image found. Did find:
/usr/local/lib/libusb-1.0.dylib: mach-o, but wrong architecture
2016-01-12 22:02:52,390 ERROR:usb.backend.libusb1:Error loading libusb 1.0 backend
dlerror: dlopen(/Library/Frameworks/openusb.framework/Versions/1.1.11/lib/openusb_backend/darwin.so, 1): Symbol not found: _usbi_devices
Referenced from: /Library/Frameworks/openusb.framework/Versions/1.1.11/lib/openusb_backend/darwin.so
Expected in: flat namespace
in /Library/Frameworks/openusb.framework/Versions/1.1.11/lib/openusb_backend/darwin.so
fail to load /Library/Frameworks/openusb.framework/Versions/1.1.11/lib/openusb_backend/darwin.so
2016-01-12 22:02:52,393 ERROR:usb.backend.openusb:Error loading OpenUSB backend
Traceback (most recent call last):
File «/Library/Frameworks/Python.framework/Versions/3.4/lib/python3.4/site-packages/usb/backend/openusb.py», line 738, in get_backend
_ctx = _Context()
File «/Library/Frameworks/Python.framework/Versions/3.4/lib/python3.4/site-packages/usb/backend/openusb.py», line 512, in init
_check(_lib.openusb_init(0, byref(self.handle)))
File «/Library/Frameworks/Python.framework/Versions/3.4/lib/python3.4/site-packages/usb/backend/openusb.py», line 506, in _check
raise USBError(_lib.openusb_strerror(ret), ret, _openusb_errno[ret])
usb.core.USBError: [Errno None] b’Unspecified kernel/driver failure’
2016-01-12 22:02:52,394 ERROR:usb.libloader:’Libusb 0′ could not be found
2016-01-12 22:02:52,394 ERROR:usb.backend.libusb0:Error loading libusb 0.1 backend
Traceback (most recent call last):
File «», line 1, in
File «/Library/Frameworks/Python.framework/Versions/3.4/lib/python3.4/site-packages/usb/core.py», line 1199, in find
raise ValueError(‘No backend available’)
ValueError: No backend available

import usb.core
from usb.backend import libusb1
be = libusb1()

TypeError: ‘module’ object is not callable

TypeError: ‘module’ object is not callable

your FAQ has errors!

all three backends are not working properly. How do you fix this error?

Your libusb install has problems. I suggest you reach libusb guys out.

I did contact them and posted my question on stack overflow but I haven’t heard from anyone. I installed libusb1 using Homebrew on my Mac OS X, however, I am getting a dlerror because the linker cannot find the backend library. Do you have any ideas on how to fix that? How did you make your backend work properly?

import usb.core
from usb.backend import libusb1
b = libusb1.get_backend()
b
print(b)
None
dev= usb.core.find()
dlerror: dlopen(/Library/Frameworks/openusb.framework/Versions/1.1.11/lib/openusb_backend/darwin.so, 1): Symbol not found: _usbi_devices
Referenced from: /Library/Frameworks/openusb.framework/Versions/1.1.11/lib/openusb_backend/darwin.so
Expected in: flat namespace
in /Library/Frameworks/openusb.framework/Versions/1.1.11/lib/openusb_backend/darwin.so
fail to load /Library/Frameworks/openusb.framework/Versions/1.1.11/lib/openusb_backend/darwin.so
Traceback (most recent call last):
File «», line 1, in
File «/Library/Frameworks/Python.framework/Versions/3.4/lib/python3.4/site-packages/usb/core.py», line 1199, in find
raise ValueError(‘No backend available’)
ValueError: No backend available

I did contact them and posted my question on stack overflow but I haven’t heard from anyone. I installed libusb1 using Homebrew on my Mac OS X, however, I am getting a dlerror because the linker cannot find the backend library. Do you have any ideas on how to fix that? How did you make your backend work properly?

How did you install libusb? Can any program linked to it work?

FYI for OSX 10.11:
I had previously installed pyusb using sudo pip3 install pyusb then subsequently installed libusb1 from source and pyusb was not finding my libusb1. I then removed the pip pyusb sudo pip3 uninstall pyusb and installed pyusb from source

python3 setup.py build sudo python3 setup.py install 

and it finds the libusb library just fine..

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usb.core.NoBackendError: No backend available #340

usb.core.NoBackendError: No backend available #340

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I am trying to start using Pyusb library to implement a USB logger for my STM32 device.

I started following the tutorial but got some error while checking the usb device connected to the PC.

import usb
import usb.util
import usb.core

dev = usb.core.find(idVendor=0x483, idProduct=0x572B)
print(dev)

Ended up with this error:
raise NoBackendError(‘No backend available’)
usb.core.NoBackendError: No backend available

I tried following up for the issue on this git but couldn’t find any proper solution.
Appreciate any help on this

The text was updated successfully, but these errors were encountered:

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