Weewx has problems finding USB device

[Hiljo Lodewijk]

Hello everyone,

I’ve been running Weewx on my Synology NAS DS216+II for about 4 years now. I always used the attached manual to install Weewx. This worked great. Untill a recent update of the OS. Suddenly Weewx cannot find the USB device of my TFA Primus anymore..

The USB device is attached. The command lsusb shows:
Bus 001 Device 002: ID 6666:5555
Bus 001 Device 003: ID f400:f400
Bus 001 Device 001: ID 1d6b:0002
Bus 002 Device 001: ID 1d6b:0003

When I run weewx I get exception 'No backend available'. More users have had this error. The problem of most users is that python cannot find the USB modules.

The strange thing is that if I run python on the command line, it cannot find the libUSB library first, but if I import it manually (import usb.backend.libusb01), it does work. See below:

$ python
Python 2.7.12 (default, May 15 2018, 03:33:53)
[GCC 4.9.3 20150311 (prerelease)] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> import usb
>>> usb.core.find()
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/lib/python2.7/site-packages/usb/core.py", line 829, in find
    raise ValueError('No backend available')
ValueError: No backend available
>>> import usb.backend.libusb01
>>> usb.core.find()
<usb.core.Device object at 0x7f3d511fb250>

So my question is that if it is possible to import the usb.backend.libusb01 library somewhere in the Weewx core (or driver) to make it run correctly again.

I already tried to import it in the WS28xx.py file, but that doesn’t work unfortunately. Any ideas for help?

Thanks in advance!

[Thomas Keffer]

It looks like the underlying "C" library is missing. Try this:

find /usr/lib -name "libusb*"

If it is missing, you may have to install it.

-tk

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[Bernhard Frieß]

Hi There,

I had the same error message as you although I was about to install weewx on OpenWRT and not on a synology running DSM. I found a solution for my problem and if you're interested you can read through it at https://groups.google.com/forum/#!topic/weewx-user/sY5TJijPPv8.

I also updated the wiki page about running weewx on OpenWRT at https://github.com/weewx/weewx/wiki/weewx-on-openwrt.

The original description gave the impression that there is only an issue with a specific driver wmr200.py while it looks to me know that all drivers are affected which are relying on USB.

Perhaps this helps you as well?

Best regards

Bernhard

[Hiljo Lodewijk]

I've managed to get the WS2800 driver working by doing the same as Bernhard has done:

Then to fix error with backend driver missing you need to help the /home/weewx/bin/weewx/drivers/wmr200.py driver file find the installed usb driver:

import usb

import usb.backend.libusb1
backend = usb.backend.libusb1.get_backend(find_library=lambda x: "/usr/lib/libusb-1.0.so")

before:

import usb

import weewx.drivers

after:

import usb

import usb.backend.libusb1
backend = usb.backend.libusb1.get_backend(find_library=lambda x: "/usr/lib/libusb-1.0.so")

import weewx.drivers

Op zondag 17 juni 2018 09:51:20 UTC+2 schreef Hiljo Lodewijk:

[vince]

On Thursday, April 11, 2019 at 12:35:22 PM UTC-7, Hiljo Lodewijk wrote:

I've managed to get the WS2800 driver working by doing the same as Bernhard has done:

Then to fix error with backend driver missing you need to help the /home/weewx/bin/weewx/drivers/wmr200.py driver file find the installed usb driver:

import usb

import usb.backend.libusb1
backend = usb.backend.libusb1.get_backend(find_library=lambda x: "/usr/lib/libusb-1.0.so")

That is going to be a problem when somebody uses a different version of the library or runs on a different operating system.  Hard-coding things like this in a 'one size fits all' piece of software is rarely a good idea.....

[Thomas Keffer]

See this thread. In that particular instance, the problem was a missing copy of ldconfig on the user's operating system.

[Hiljo Lodewijk]

I do agree that there is a problem with my configuration (Synology NAS). But i've tried many ways to fix this problem. Currently this is the fastest solution.

Op donderdag 11 april 2019 22:41:46 UTC+2 schreef Thomas Keffer:

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[Thomas Keffer]

That's fine. Just remember to reapply the fix if/when you upgrade. 

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