about // doc

Control Lab Instruments with PyVISA in Scientific Linux 5 (v2.0)

Last modified: June, 2013

This is an improved tutorial based on the previous post. Now the scenario is that I need to use a NI GPIB-US-HS adapter to control some lab equipments with GPIB.

Before installation

Required:

A computer with USB support
GPIB-USB-HS adapter from National Instrument
Operating system: Scientific Linux 5.x, 32-bit
NI-VISA, Linux version
NI-488.2 GPIB driver, Linux version
PyVISA

Here are some words about OS choice: There is already Scientific Linux 6.x at the time of writing. So why still use SL 5? The reason is the official NI driver of GPIB-USB-HS adapter is only supported by Linux kernel up to 2.6.24 (see the README of NI-488.2 package). According to this post, Linux developers changed the license of USB driver APIs since kernel 2.6.25 which prevented proprietary drivers from using the kernel. If you want to go for NI drivers like I do, there is no choice but going for old kernels (<=2.6.24). Since SL 6.x comes with kernel > = 2.6.32, SL 5.x is the only choice left. Also remember to select 32-bit SL 5.x since 64-bit is not supported yet.

Surely there are ways around. One example is to use the open-source Linux-GPIBdriver. I heard it worked pretty well for some people. But in this post I will focus on the NI driver sets.

If you are using a PCI-GPIB card instead, you can install SL 6.x (easier to work with than SL 5.x). The rest of the tutorial stay the same.

Install NI drivers

First install dependencies

sudo yum install kernel-devel gcc glibc-devel make

Now install NI-488.2. Download the package from NI’s website, unpack, and run

sudo ./INSTALL

For NI-VISA, download the iso image from NI’s website,

su 
mkdir /mnt/iso
mount -t iso9660 -o loop your-NI-image.iso /mnt/iso
cd /mnt/iso
# read README before proceeding
./INSTALL

Very standard procedures.

Install PyVISA

SL 5.x is old. The default Python version is 2.4. Instead of messing with ctypes in Python 2.4 as I did in the previous post, I find pythonbrew is a nice tool to have multiple Pythons with different versions in the same box.

First install the dependency:

sudo yum install readline-devel

Now follow the instructions on pythonbrew Github page and install it:

curl -kL http://xrl.us/pythonbrewinstall | bash

and append

[[ -s $HOME/.pythonbrew/etc/bashrc ]] && source $HOME/.pythonbrew/etc/bashrc

to file ‘$HOME/.bashrc’, and re-source the bashrc file

source ~/.bashrc

Now I can easily install the newest Python in SL 5.x like

pythonbrew install 2.7.3

This will install Python 2.7.3 in pythonbrew’s separated environment (located in ‘~/.pythonbrew’). Now use Python 2.7.3 as the default Python version:

pythonbrew switch 2.7.3

Even better, PyVISA is in PyPI (Python Package Index) repository now. So install PyVISA can be as easy as

pip install pyvisa

That’s it. You can hook the computer up with an equipment and test as I did in the previous post.

NOTE: If you have RAM larger than 3GB, and have errors related memory mapping, you can append string like mem=4096M as the boot option in /boot/grub/grub.conf. This solves the problem sometimes. This is because we are using 32-bit system here, and it cannot address RAM above 3GB.