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pyvisa / pyvisa-py

A pure python PyVISA backend
https://pyvisa-py.readthedocs.io
MIT License
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GPIB Instrument Support for Windows #105

Closed tkzilla closed 5 years ago

tkzilla commented 7 years ago

Is there a plan to support GPIB instruments on Windows? linux-gpib support is nice, but there are some instruments/software that only run on Windows and they use GPIB loopback addresses.

MatthieuDartiailh commented 7 years ago

I am not aware of any library other than visa providing GPIB support on windows, if you do please let us know.

tivek commented 6 years ago

GPIB drivers on Windows sit "below" the Visa layer. As far as I know, the GPIB C API exposed by gpib-32.dll/obj on Windows is the same as the C API of linux-gpib. So the question then becomes whether there are Python bindings for GPIB that work both on Linux and Windows.

There is an attempt to build the linux-gpib Python bindings on Windows/Cygwin: https://sourceforge.net/p/linux-gpib/mailman/message/36149135/

Instead of building a Python module written in C like linux-gpib does, another way would be to use ctypes or cffi to call the GPIB C functions. The old gpib-devices library does that quite successfully on both Windows and Linux, see libgpib.py. However, that is only a straightforward wrap of the GPIB C API and some effort will be required to have the same interface as linux-gpib.

EDIT: To scratch my own itch independent of pyvisa-py I am planning to implement a ctypes wrapper that mimics linux-gpib but works under Windows as well. I would be happy to see it work with pyvisa-py. As I am new to the project any help and pointers are most welcome.

MatthieuDartiailh commented 6 years ago

This sounds very interesting @tivek. Please keep us posted on your progress. As soon as you have something that could be supported by pyvisa-py please let us know and we will try to provide some guidance on how to proceed from there.

tivek commented 6 years ago

The rough first commit of linux-gpib-like bindings that also work on Windows is here: https://github.com/tivek/gpib_ctypes

I implemented the low-level gpib module from scratch by referring to linux-gpib Python bindings docstrings, NI GPIB C docs as well as linux-gpib docs. However, the nice, object-oriented, capital-letter Gpib module that pyvisa-py is using is copied directly from the linux-gpib project. Since linux-gpib is GPL2, that means for the time being gpib_ctypes is given under GPL2.

So far I tried out the code on Windows with NI GPIB-USB-HS, driver version 3.1.0.49154. I plan to also test it on Debian with linux-gpib in the coming days.

How to try it out:

# monkey-patch us to take precedence over eg. linux-gpib's gpib modules
from gpib_ctypes import make_default_gpib
make_default_gpib()

import visa
rm = visa.ResourceManager('@py')

rm.list_resources()
# output on my Windows machine: ('GPIB0::14::INSTR', 'GPIB0::23::INSTR')

hp = rm.open_resource('GPIB0::23::INSTR')
hp.query("*IDN?")
# output: 'HEWLETT-PACKARD,4284A,0,REV01.20\n'

Bugs are to be expected. Testers welcome!

tivek commented 6 years ago

Update on Linux tests: the above snippet works fine with linux-gpib on 201801 Arch Linux and the NI GPIB-USB-HS adapter (I only had to put board_type = "ni_usb_b" in /etc/gpib.conf to make the hardware work).

MatthieuDartiailh commented 6 years ago

@tivek any plan on publishing a first release soon ?

tivek commented 6 years ago

@MatthieuDartiailh apologies for the late reply, was offline and out of town.

Basically, https://github.com/tivek/gpib_ctypes works for us (TM) in the lab. It can be installed and tested right now using: pip install git+https://github.com/tivek/gpib_ctypes.git

Of course I can make an alpha release on pypi, but I was hoping for a bit more testing by others before my first ever release there. Open for any advice you can give.

MatthieuDartiailh commented 6 years ago

I can try to give it a go perhaps sometimes next week. I will keep you posted. After, as release go, I tend to hold back quite a bit myself, but actually releasing early usually makes sense. I do not find any large bug I think it would be worth releasing that way I will document it in PyVISA-py for the next release (and make the manual patching superfluous).

tivek commented 6 years ago

Sounds great. Please let me know what you find. For now the monkeypatching method above works ok so maybe start with that.

And thank you for the advice on releasing early. More eyes will catch more bugs. I will do so in the coming days.

kpckpc commented 6 years ago

If linux-gpib is already supported, you might want to have a look at the script I created for octave https://wiki.octave.org/Instrument_controlpackage#Windows.28cygwin.29 This allowed me to use software designed for linux-gpib wihtout any changes on Windows.

mb711 commented 5 years ago

Tivek,

I'm not sure if I found a bug, but the error I'm seeing is stumping me. I posted to the below link

https://github.com/tivek/gpib_ctypes/issues/1