Re: NI 6602 - comedi_data_read(..) takes 4ms (RTAI 3.3)

Hello Arno,

The procedure is to simply call rt_get_cpu_time_ns(); in the beginning of
the task,
immediately before and after reading encoder values, and subracting the
difference.
Same thing with Analog out,  and finally at the end of the task for total
Task execution-time.

Another interesting issue was found. Reading the encoder also has ~~200us
execution time
every two seconds if the ethernet cable is connected during boot time. The
analog out or the
rest of the task's execution times are not affected.
   It really seems like there's a conflict of some sort. Whether this has to
do with the comedi-driver
or the hardware, I do not know.
   I will e-mail you a graph shortly showing the behavior of the task. (If
someone else is interested to
see it, notify me).

Worth mentioning is that unlike the regular 2 second ~~200us execution
times, the really nasty 4ms
delays are not regular at all.  But usually comes 1-3 times within 20
seconds without much pattern.

Regards,
Camino

On 3/28/06, Stienen, A.H.A. (CTW) <a.h.a.stienen_at_utwente.nl> wrote:
>
> janne wrote:
> > I'm running a single task (about 4KHz) that reads encoder values and
> > ouputs an analog signal.
> > When running for 20 seconds, there are usually a few instances ( 1 - 3)
> > where reading values
> >  from the encoder takes about 3800 - 4000 us. Which is, of course awful.
>
> How do you measure this? What is the procedure?
>
> FWIW, I'm using the same card and haven't noticed similar problems. Then
> again, I haven't looked either...
>
> Arno.
> --
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