At 04:08 2007-09-17, you wrote:
>--- In <ts-7000%40yahoogroups.com>
>"fabianmejia" <>
>wrote:
> >
> > Hi All,
> >
> > I am under development of a capture system. I need to sample about
> > 200Hz. That is, about sampling each 0.005 seconds.
> >
> > I have it working using the Jim Jackson's adc_logger.
> >
> > Unfortunatelly, this can't accomplish the job as it's accurate
>about 10ms.
> >
> > So, I decided using gettimeofday. Oh surprise!!! It doesn't work
> > properly. microsecond precision? Forget about it. Readings give me
> > mumbers like this:
> >
> > 510000
> > 530000
> > 550000
> >
> > It sounds like 10msec precision.
FWIW, there's an API to verify this: clock_getres, used as
#include <stdio.h>
#include <stdlib.h>
#include <time.h>
int main ()
{
struct timespec resolution, now;
printf ("Size of __time_t: %d\n", sizeof (__time_t));
printf ("Size of int: %d\n", sizeof (int));
clock_getres (CLOCK_REALTIME, &resolution);
printf ("Resolution %ld sec: %ld nsec\t(%f sec)\n"
, (long)resolution.tv_sec, (long)resolution.tv_nsec
, (double)resolution.tv_sec +
1.0e-9*resolution.tv_nsec);
clock_gettime (CLOCK_REALTIME, &now);
printf ("Time now: %ld:%ld (seconds:nanoseconds)\n"
, (long)now.tv_sec, (long)now.tv_nsec);
return 0;
}
On a vanilla TS-7400 board this gives the clock resolution as 0.01 seconds.
Mel.
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