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Date: Mon, 23 Aug 2010 22:23:35 +0200
From: Gilles Chanteperdrix <gilles.chanteperdrix@xenomai.org>
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Subject: Re: [Xenomai-help] periodical task in posix skin
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To: ramon costa <ramoncostacastello@domain.hid>
Cc: Xenomai help <xenomai@xenomai.org>

ramon costa wrote:
> Hi,
> 
> I have developed a very simple task in native code and it works fine
> (included in native.tar.gz). This
> simple task generates a square waveform through the parallel port ( and also
> the speaker).
> 
> Currently I'm trying to transform this code into the POSIX skin (Makefile
> and .c included in posix,tar.gz).
> Unfortunatelly It does not work, although the parallel port shows a square
> waveform its period is not the desired
> one (0.1ms), its period is very small. This makes the system to freeze.
> 
> It seems that pthread_wait_np is not working properly, or may be I'm not
> using pthread_make_periodic_np
> properly. I used it in the following way :
> 
>         #define PERIOD 100000
> 
>         clock_gettime      ( CLOCK_REALTIME, &now);
>         pthread_make_periodic_np (pthread_self(), &now, (struct timespec
> *)PERIOD);

Well, the reason why this does not work is obvious, I am even amazed
that it does not cause a segmentation fault, but you could check
pthread_make_periodic_np return value to have a clue.

> I also have tried
> 
>        struct timespec period;
>        period.tv_sec=0;
>        period.tv_nsec=PERIOD;
> 
>         clock_gettime      ( CLOCK_REALTIME, &now);
>         pthread_make_periodic_np (pthread_self(), &now,&period);
> 
> Although both compile and execute, non of them works fine to me. Any clue ?

Here I have no clue, more exactly, I would need to see the whole code to
see what is going wrong. But again, checking pthread_make_periodic_np
return value, and looking at the documentation would help. My guess
would be that at the time of pthread_make_periodic_np, "now" is a date
in the past.

And pthread_make_periodic_np/pthread_wait_np are supposed to help
porting code from RTLinux, they should not be used in new programs. You
should be using clock_gettime with the TIMER_ABSTIME flag.

-- 
					    Gilles.