Hi,
A few weeks ago, Tony Schanzle and M. Rowe
independently asked people for experiences with
LabVIEW under Linux on the info-labview
mailing list.
I compiled the following from our initial experience so far
for the info-labview mailing list.
As I make some comparisons to fltk and as we want to use
real-time Linux with either Labview or fltk. Therefore, I
will also send this message to the real-time Linux and
fltk mailing lists [5]. I hope this will be of interest
to some of you.
Best regards,
Arnold Niessen.
Some preliminary experiences with Labview and Linux
---------------------------------------------------
Introduction
------------
We are looking for a user-friendly platform-independent environment
to control an experimental prototype set-up, which is
controlled via a PCL-720 digital I/O card. We are currently using
* a PC with Pentium Pro 180 MHz
* Linux kernel 2.0.35 for non Real-Time tasks,
together with the real-time extension rtlinux-9H [1] for
for real-time data acquisition (up to
multiple kHz sample frequency).
We will soon upgrade to a newer kernel and rt-version, which
is reported to have even lower overhead for periodic tasks.
* For user-interface and prototype control we are considering
either Labview or the platform-independent and open-source
fltk [2].
* For graphical real-time output we are considering
either Labview or writing a scope-like extension
for fltk.
Installing
----------
We have installed Labview 5.0beta on a PC with some old
Slackware distribution (Linux is too stable - there
never was a need to upgrade :-), running
kernel 2.0.35/rtlinux-9H.
We later upgraded to RedHat 5.2, running kernel 2.0.36,
without any problems.
During the Labview installation, we encountered the following
problems:
1) the file INSTALL.norpm calls cpio, but the option
-d (create leading directories where needed) is missing,
resulting in two missing directories in the target directory.
2) the file /usr/local/lv50/cintools/lvmkmf is incorrect (it
is in fact a copy of the header file hosttype.h); just replacing
it with the HP-UX version suffices.
Performance benchmarking
------------------------
As we want to have a fast running chart as graphical output for
our set-up, I benchmarked a trivial example, of one
chart which shows the wall-clock time in milli-seconds (module 1000),
to produce a running sawtooth. This chart produces reasonable
output, but with some visible interruptions (the `data-collection'
code part has not yet been implemented in the real-time environment).
The table below shows how many points per second are drawn,
for the three different chart update modes. This has been
done both on the X display of the PC and via a 10 Mbit/s
ethernet connection on a HP X-terminal.
strip | scope | sweep
--------+-----------+-------------------------------------
300-900 | 5400 | 4800 On PC XFree 3.3.1
270-450 | 3300-4300 | 2000-3000 10 Mbps/HP-Envizes p-series X-terminal
(measurements in points drawn/second)
These numbers were slightly lower for real measured data,
which was obtained from our self-written device driver.
Conclusion
----------
Our preliminary conclusion is that these charts are probably
capable of displaying real-life info up to approximately
1 or 2 k-sample/second, using the scope mode. Real-time data
collection using FIFO's or real-time Linux is still required,
of course.
Although this may be fast enough for many applications, it is
much slower than dedicated C code (for example, a very lean
single scope program, based on fltk [2], can easily show more
than 90.000 pixels/second on the same PC).
References
----------
[1] Rtlinux info: www.rtlinux.com and www.rtlinux.org
`RTLinux is an extension to Linux that handles time-critical
tasks. In RTLinux, a small hard-realtime kernel and standard
Linux share one or more processors, so that the system can be
used for applications like data acquisition, control, and
robotics while still serving as a standard Linux workstation.'
`RTLinux is open-source. The first version was implemented
mainly by Michael Brabanov. The software is under GNU Library
Public License and is freely downloadable.'
`A hard-realtime response of under 4microseconds interrupt
response on a PII is claimed on their website'
[2] Fltk info: fltk.easysw.com
`FLTK is a C++ GUI toolkit for UNIX® (X Window System)
and Microsoft® Windows® (NT 4.0, 95, and 98). FLTK
provides a complete set of GUI widgets and supports OpenGL.'
This library is free software under the terms of the GNU
Library General Public License.
[3] Labview info: www.natinst.com/labview
[4] Linux info: www.linuxhq.com
www.redhat.com
www.lwn.net
www.linux.com
www.slackware.com
www.freshmeat.net
and many others
[5] Mailing list addresses: [EMAIL PROTECTED]
[EMAIL PROTECTED]
[EMAIL PROTECTED]
--
A.J. Niessen | Philips Research Laboratories
Building WY 2.51 | Prof. Holstlaan 4
Phone: (+31-40-27)42715/43173 | 5656 AA Eindhoven
Fax: (+31-40-27)44648 | The Netherlands
E-mail: [EMAIL PROTECTED]
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----
For more information on Real-Time Linux see:
http://www.rtlinux.org/~rtlinux/
