--- In "ka7ftp" <> wrote:
>
> HI Charlie,
>
> Good catch on the schematics, I fixed that. The correct schematics are there
> now.
>
> I left the HZ as it was in the Kernel. In my initial testing with out the
> variable HZ patch I never saw the offset below the ms level. Tho, I still
> need to do some more testing.
>
> With the 2.6 kernel I believe the PPS support is still in the serial driver,
> is that right? My PPS module uses one of the GPIO lines.
Yes and no. Most systems take the GPS PPS on the DCD pin, but there is support
for parallel port IO too (shm pps ?). There is a PPS line discipline (18) so
it gets handled properly in the kernel. Since 2.6.34 most of the linuxPPS
patch is now in the kernel proper.
>
> Yes, the NTPD config uses the PPS API driver.
>
> One question for those who probably have more experience than me. I do see
> the PPS offset "oscillate" from plus and minus MS, SHouldn't is settle down
> after some time?
You should see offset settle down to a small number of microseconds when using
PPS, not 1 mS. And it shouldn't take too long to settle, but I guess that's a
pretty common issue. There are some nice scripts out there to plot ntpd
statistics.
If you still have too much time on your hands :) you could use the onboard A/D
and a few components to stabilize the 14.74 MHz oscillator:
http://rembl.org/index.php/2008/12/31/thermostat-for-system-clock/
regards ....... Charlie
>
> Thanks for the concise input!
>
> len
>
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