Re: low level I/O (GPIB, USBTMC, VXI11)

[Julien Salort]

Le 23 nov. 2012 à 23:18, Stefan Mahr <address@hidden> a écrit :

> Julien Salort wrote:
>> That makes 3 packages for the same purpose. However, I don't know about
>> yours, but mine uses National Instruments libraries for VISA and DAQmx,
>> and free libraries for FireWire cameras and Modbus.
> >
> > I guess the NI part is not compatible with octave-forge policy of not
> > encouraging using proprietary software.
> 
> I wrote the toolbox for my work, where I use Windows and Linux. Since NI VISA 
> is very complicated to install on Ubuntu - if even possible on actual 64bit 
> installation - I had to find other ways. Besides that, I think linking to NI 
> VISA would violate the GPL.

It is my understanding you can link with whatever you want for your personal 
usage.
However, DISTRIBUTING a binary that links with NI VISA definitely violates the 
GPL.
That is why I don't distribute binaries, only source code.

Besides, my code should compile with libgpib and openvisa, even though I 
haven't tested. The source code in itself does not forbid anything.

Personnally, I haven't been able to install NI VISA on Ubuntu reliably. That is 
why I use Scientific Linux, which is an officially supported distribution. It 
is much easier to install National Instruments drivers of Scientific Linux (it 
installs right out of the box). Of course, it would be easier if their drivers 
were free. I filed a complaint already. You may complain too. Maybe if many 
people complain, they might change their way ?

> For linux you can talk to all instruments without using any proprietary 
> software. For windows you still have a problem if you don't have serial or 
> LAN based instruments or at least a VXI11-GPIB gateway.

I have a very heterogeneous environment for my experimental setups (Windows XP, 
Macintosh and Linux). The nice thing with NI drivers is that the same code 
works on those three platforms out of the box, and it allows to communicate 
with a very wide range of devices. Considering how expensive a PXI is (for 
example), I definitely need a driver that allows me to use all its functions... 
My colleagues wouldn't understand if I use a driver that wouldn't allow me to 
use all its capabilities.

> Of course, the best way to communicate with instruments would be using the 
> VISA interface, but you need a (working) free VISA library first.

I agree a free VISA (and DAQmx) would be much nicer. I personally don't have 
the time nor the knowledge to work on that.

In a mean time, I need to work, and the NI VISA (and DAQmx) library does work 
on many platforms, and can be freely downloaded. I regret that it is not free 
and that you have to agree to their restrictive license terms.