GPIB on Ubuntu 12.04

Last modified: Jun, 2013

I have been using PyVISA to control GPIB lab instruments. The only problem was I used NI-VISA as the VISA layer. Since I also used GPIB-USB-HS adapter from NI, I have to use 32-bit Scientific Linux 5.x. While the whole package still looked much better than using the bloated LabVIEW, it was increasingly a pain because I couldn’t have things like matplotlib working out of box in SL 5.x in the data processing stage. Yes, SL 5.x was a stable (legacy) system. But there were things (like Octave fonts, old Emacs, etc.) in SL 5.x making me feel annoyed from time to time.

I was always thinking if I could have GPIB control from a much more modern system (sorry, SL 5.x grandpa) like Ubuntu 12.04, it would be great. Here is how.

Download linux-gpib source from here. Extract the tar ball, cd into the source directory, and do the routine compiling thing

./configure
make
sudo make install

After that, a group called “gpib” will be created. Add yourself to this group:

sudo usermod -aG gpib username

Also link the GPIB library to library path:

cd /usr/lib
sudo ln -s /usr/local/lib/libgpib.so.0 .

If you use GPIB-USB-HS adapters like me, go and edit /etc/gpip.conf and change the board_type in interface section to

board_type = 'ni_usb_b'

Now, if you plug in a GPIB-USB-HS cable to the laptop, you will see /dev/gpib[0~15]. But they are owned root. To write to GPIB device in userspace, udev is the way to go. Create /etc/udev/rules.d/99-ni_gpib_usb.rules with the content below:

SUBSYSTEM=="usb", ACTION=="add", ENV{DEVTYPE}=="usb_device", 
ATTR{idVendor}=="3923", ATTR{idProduct}=="702[ab]", 
MODE="660", GROUP="gpib", SYMLINK+="usb_gpib"
SUBSYSTEM=="usb", ACTION=="add", ENV{DEVTYPE}=="usb_device", 
ATTR{idVendor}=="3923", ATTR{idProduct}=="702[ab]", 
RUN+="/lib/udev/ni_usb_gpib"
KERNEL=="gpib[0-9]*", ACTION=="add", MODE="660", GROUP="gpib"

I take this udev rule from this page and it just works like a charm after a reboot. What it does is udev recognizes the GPIB-USB-HS cable once it is plugged in, and make all GPIB devices writable to group gpib.

At last, run

sudo gpib_config

Actually this command line should be run each time the linux-gpib drivers are loaded. If everything goes well, the GPIB communication should work by now. You can test it with an interactive GPIB tool (comes with linux-gpib) ibtest

ibtest

Note that you should be able to run it as a user in gpib group, otherwise udev is not configured right. Type ‘d’ –> type GPIB port –> type ‘w’ –> type ‘*IDN?’ –> type ‘r’ –> enter, and you should read some equipment information back. The Python bindings of linux-gpib are enable by default during the compiling. To use it in Python, here is a quick start:

import gpib
h = gpib.dev(0, 20)  # Locate your GPIB device and get the device handle
gpib.write(h, '*IDN?')   
gpib.read(h, 1024)   # Read 1024 bytes max

You can also locate the device with gpib.find() with the device alias (a string) if you specify it in the device section of /etc/gpib.conf. For more info, look at

help(gpib)