Hi Tormod & others
Looks we are the same page ... yes I will tidy up permissions later ... and
the issue relates to the python version. I downloaded pyusb not
python-usb"or "python3-usb.
But I am winning!!!!! yes although still need help.
My process has been as follows (bear in mind I have the same problem with
my raspbian & ubuntu 16.04 systems - I am working on the Raspberry Pi
because it is way easier to reinstall the OS than on my desktop :)
Script:
1
2 import usb.core
3 import usb.util
4 help()usb)
5 dev = usb.core.find()
6 print(dev)
7
8 dev.set_configuration()
lines 4,5 and 6 execute fine = I get the expected outcome
Diagnostic:
AS it only the last line that really matters:
File
"/home/pi/.local/lib/python3.5/site-packages/usb/backend/libusb1.py", line
595, in _check
raise USBError(_strerror(ret), ret, _libusb_errno[ret])
usb.core.USBError: [Errno 13] Access denied (insufficient permissions)
Check permissions:
pi@raspi3:~/.local/lib/python3.5/site-packages/usb/backend $ ls -l
total 108
... the relevant one is:
-rwxrwxrwx 1 pi pi 35299 Jan 20 13:31 libusb1.py
... so anyone can execute ????
... so if I run libusb1.py in idle I get:
File "/home/pi/.local/lib/python3.5/site-packages/usb/backend/libusb1.py",
line 702, in <module>
class _LibUSB(usb.backend.IBackend):
AttributeError: module 'usb' has no attribute 'backend'
... so it looks like the permission problem = no backend
... but if I
root@raspi3:/home/pi/.local/lib/python3.5/site-packages/usb/backend#
python3.5 libusb1.py
Traceback (most recent call last):
File "libusb1.py", line 30, in <module>
import usb.util
ImportError: No module named 'usb'
in module libusb1.py:
29 from ctypes import *
30 import usb.util
so it seems the permission that is failing is the ability of backend to
import usb.util which my script does not seem to have a problem with.
Now checking ctypes there are three copies at:
i) /usr/lib/python2.7/ctypes
ii) /usr/lib/pypy/lib-python/2.7/ctypes
iii) /usr/lib/python3.5/ctypes
permissions on the above are all ok ...
now it gets interesting ... if I run (in idle) the script copied from
libusb1.py:
from ctypes import *
import usb.util
.... and add help(usb.util) I get expected 'help' output.
so there is a difference. BUT .. idle is python3.5 and pyusb is only
installed in python3.5 ... which usb.util does libsub1.py call?
Am I on the right track here?
I have now installed pyusb via pip to python2.7 ... my script now runs iin
terminal as user!!! looks like a win!
checking with ~$ python --version it seems the system defaults to 2.7
I have installed pyusb to 2.7 ... and checked it is there permissions are
ok plus IDLE for 2.7
Now I need more help.
While I can run the script from the terminal I can't from my IDEs I still
get
File "/home/pi/.local/lib/python2.7/site-packages/usb/backend/libusb1.py",
line 595, in _check
raise USBError(_strerror(ret), ret, _libusb_errno[ret])
USBError: [Errno 13] Access denied (insufficient permissions)
which I would understand if it is run from 3.5,but this is from 2.7????
cheers
Charles
On Tue, 22 Jan 2019 at 11:16, Tormod Volden <lists.tor...@gmail.com> wrote:
> On Mon, Jan 21, 2019 at 5:28 AM charles wilson wrote:
> > On permissions, I had checked/changed permissions previously but
> re-checked and found a missed one in /python3.5/site-packages/usb/backend-
> happened to be libusb1.pywhich was flagged - all fixed now
>
> > I had also not checked the /dev/*USB* but did and gave necessary
> permissions
>
> > drwxrwxrwx 3 pi pi 4096 Jan 20 13:31 backend
> > -rwxrwxrwx 1 pi pi 8739 Jan 20 13:31 control.py
> > still get the same error diagnostic which still ends usb.core.USBError:
> [Errno 13] Access denied (insufficient permissions)"
>
> > so basically no change.
>
> Charles,
>
> The permission issue is with the USB device node under
> /dev/bus/usb/*/* and not the python library files. It looks like you
> have messed up all library files permissions now - they need not and
> should not be writeable for everybody. You'd better reinstall the
> packages to tidy up.
>
> >
> > Now the interesting bit. I tried running as root
> > root@raspi3:/home/pi/PyProj# python3.5 pyusb_1.py
> > Traceback (most recent call last):
> > File "pyusb_1.py", line 2, in <module>
> > import usb.core
> > ImportError: No module named 'usb'
> >
> > same result if I simply sudo python3.5 pyusb_1.py
> >
> > when I run python3.5 from the terminal and get the python >>> prompt
> there is no trouble with 'import' and checking with 'help(usb)' shows the
> module is there and accessible.
> >
> > Interesting though is that I have the same problem on all linux, so
> whatever I did wrong I did it each time. I have tried installing pyusb with
> PIP and sudo apt-get but it makes no difference.
>
> Note that your Raspberry Pi has both python 2 and python 3 installed.
> The Debian package "python-usb" is for Python 2 and the package
> "python3-usb" is for Python 3.
>
> Regards,
> Tormod
>
>
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