comedi and rtai 3.1

Wolfgang Pichl pichl at
Mon Oct 4 16:18:27 CEST 2004

On Fri, 1 Oct 2004, Peter Dettori wrote:
> Hi,
> I am trying to build rtai-3.1-test5 with comedi support.  I have comedi
> comedi-0.7.68 and comedilib-0.7.21 installed.
I have tried the same thing last week and did not get it to work. The
kernel-space RTAI support in Comedi works very well, but the user-space
LXRT interface seems to be buggy.

> I then noticed in a september post
> (
> that it should work with comedi cvs.  Is that right?

Unfortunately not. My personal experience:
If I use the latest stable comedi and comedilib, RTAI does not even
compile if the Comedi-LXRT is enabled.
Using the comedi cvs, it does compile, but the comedi-rtai module cannot
be loaded due to unresolved symbols.
Please note: in the compilation of RTAI, the header comedilib.h from
the *comedi* package, not that from *comedilib* must be used. This
information was somewhere in an earlier posting in this mailing list.
However, even if this is done correctly, it does not work.

One last question: if you only want analog input, do you really need LXRT?
Using the "command" facility of comedi and the kernel-based RTAI support,
you get a data stream in real-time to the comedi device (e.g.
/dev/comedi0), which your application can read continuously in
non-realtime. At least for me, this turned out to be completely
sufficient, so I did not bother any more about LXRT.

best regards
Wolfgang Pichl

a.o.Prof.Dr.Wolfgang Pichl
Institut f. Materialphysik         University of Vienna
Boltzmanngasse 5
A-1090 Wien     AUSTRIA

Tel. (+43 1) 4277 51382
Fax  (+43 1) 4277 9513
email pichl at

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