On 1/20/2021 4:41 PM, Jonas Malaco wrote:
On Wed, Jan 20, 2021 at 6:20 PM Steve Kranish via pyusb-users
<pyusb-users@lists.sourceforge.net> wrote:
This is a widely reported problem which has just been left dangling for
many people. I have yet to see a complete, meaningful resolution.
This is not true.
The solution, as you have already gathered, is to install libusb.
As mentioned below, I have installed libusb 1.0.23b7
It installs 32 and 64 bit versions, or at least 32bit and 64 bit
directories. The DLLs ARE different.
I have copied the 64 bit library to c:\Windows\System32 AND my python
working directory, where the py files are.
By the way, you haven't mentioned whether you're running 32 or 64 bit
Windows and Python.
Windows 7 - 64 bit, Python 3.85, 64 bit
I have libusb-1.0.dll in c:\windows\system32 AND the directory where my
python script exits. I still get the “No backend available” error.
Once common 64-bit Windows problem is that 64-bits DLLs go in
C:\Windows\System32 while 32-bit DLLs need to go in
C:\Windows\SysWOW64.
Perhaps that's your issue?
The 'library installation' directory is
C:\Users\skranish\AppData\Local\Programs\Python\Python38\lib\site-packages\libusb
I have used MS Process Monitor to see if libusb-1.0.dll is ever
accessed. Python does look for it (QueryDirectory) in
C:\Users\skranish\AppData\Local\Programs\Python\Python38\lib\site-packages\libusb
and my working directory, but there is nothing in the log that indicates
the file was ever accessed. It never looked in System32 or SysWOW64
Nonetheless, I put the 32 bit library in C:\Windows\SysWOW64.
and the 64 bit library in C:\Windows\System32.
I think I already had it that way.
It does seem bass-ackwards to me.
Perhaps this is of note? pyusb 1.1.0 should be the 64bit version
pyUsb installs in
C:\Users\skranish\AppData\Local\Programs\Python\Python38\lib\site-packages\pyusb-1.1.0.dist-info
The files in this directory are:
Directory of
C:\Users\skranish\AppData\Local\Programs\Python\Python38\lib\site-packages\pyusb-1.1.0.dist-info
01/17/2021 04:53 PM <DIR> .
01/17/2021 04:53 PM <DIR> ..
01/17/2021 04:53 PM 4 INSTALLER
01/17/2021 04:53 PM 1,513 LICENSE
01/17/2021 04:53 PM 2,176 METADATA
01/17/2021 04:53 PM 2,340 RECORD
01/17/2021 04:53 PM 0 REQUESTED
01/17/2021 04:53 PM 4 top_level.txt
01/17/2021 04:53 PM 92 WHEEL
7 File(s) 6,129 bytes
That is all!
After copying the dll again (as above), and running again, I find that
it DOES find a backend.
According to Process Explorer, there is now an QueryNameInformationFile for:
C:\Windows\System32\libusb-1.0.dll (because the program explicitly
looks for it there!)
in addition to accessing libusb-1.0.dll in the 'library install' directory.
Perhaps I had the wrong version of the library somewhere?
Thanks
Steve
import usb.core
import usb.util
from infi.devicemanager import DeviceManager
dm = DeviceManager()
devices = dm.all_devices
for i in devices:
try:
print ('{} : address: {}, bus: {}, location:
{}'.format(i.friendly_name, i.address, i.bus_number, i.location))
except Exception:
pass
import usb.backend.libusb1
backend = usb.backend.libusb1.get_backend(find_library=lambda x:
"C:\\Windows\\System32\\libusb-1.0.dll")
print(backend)
dev = usb.core.find(backend=backend, find_all=True)
print(dev)
def EnumerateUSB(): #I use a simple function that scans all known USB
connections and saves their info in the file
with open("EnumerateUSBLog.txt", "w") as wf:
counter = 0
for d in dev:
try:
wf.write("USB Device number " + str(counter) + ":" + "\n")
print("USB Device number " + str(counter) + ":" + "\n")
wf.write(d._get_full_descriptor_str() + "\n")
print(d._get_full_descriptor_str() + "\n")
# wf.write(d.get_active_configuration() + "\n")
wf.write("\n")
counter += 1
except NotImplementedError:
wf.write("Device number " + str(counter) + "is busy." +
"\n")
wf.write("\n")
counter += 1
except usb.core.USBError:
wf.write("Device number " + str(counter) + " is either
disconnected or not found." + "\n")
wf.write("\n")
counter += 1
wf.close()
EnumerateUSB()
_______________________________________________
pyusb-users mailing list
pyusb-users@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/pyusb-users
