[ntp:questions] question about logs of PPS

Ulrich Windl Ulrich.Windl at RZ.Uni-Regensburg.DE
Fri Jun 22 15:48:08 UTC 2007


Christian Pinedo Zamalloa <christian.pinedo.zamalloaNOSPAM at NOKKgmail.com> writes:

> hi all,
> 
> I'm a newbiew on NTP services, but anyway I'm trying to setup a Stratum1
> server with the following hardware and software:
> 
> - GPS Motorola Oncore M12
> - Server:
>     - CentOS 3.8
>     - Linux kernel 2.4.33.3
>     - ntp 4.2.2p4
>     - PPSKit 2.1.7
> 
> I have configured the /etc/ntp.conf and /etc/ntp.oncore0 files and all
> seems good but the logs. In the /var/log/messages i see after several
> hours I started the NTPD daemon:
> 
> May  9 13:29:07 khronos sshd(pam_unix)[1052]: session opened for user
> jtbpizac by (uid=0)

These are debugging messages that you can enable or disable, depending on your
personal taste.

> May  9 13:29:07 khronos kernel: hardpps: PPSJITTER: jitter=330839,
> limit=13208

Jitter exceeded. Use the source, Luke ;-)

> May  9 13:29:13 khronos kernel: hardpps: new frequency -217491 >> 4 ==
> -13594
> May  9 13:29:13 khronos kernel: hardpps: new pps.freq=-13593 (add 37)

hardpps frequency update by 37 units (to roughly 13.593PPM)

> May  9 13:29:20 khronos su(pam_unix)[1096]: session opened for user root
> by jtbpizac(uid=501)
> May  9 13:29:29 khronos kernel: hardpps: new frequency -217098 >> 4 ==
> -13569
> May  9 13:29:29 khronos kernel: hardpps: new pps.freq=-13568 (add 24)
> May  9 13:29:37 khronos kernel: hardpps: PPSJITTER: jitter=334175,
> limit=10732
> May  9 13:29:45 khronos kernel: hardpps: new frequency -216445 >> 4 ==
> -13528
> May  9 13:29:45 khronos kernel: hardpps: new pps.freq=-13527 (add 40)
> May  9 13:30:07 khronos kernel: hardpps: PPSJITTER: jitter=294411,
> limit=4864
> May  9 13:30:09 khronos kernel: hardpps: PPSJITTER: jitter=302386,
> limit=298056
> May  9 13:30:17 khronos kernel: hardpps: new frequency -434869 >> 5 ==
> -13590

shift constant updated from 4 to 5.

> May  9 13:30:17 khronos kernel: hardpps: new pps.freq=-13589 (add -61)
> May  9 13:30:37 khronos kernel: hardpps: PPSJITTER: jitter=290707,
> limit=6260
> May  9 13:30:39 khronos kernel: hardpps: PPSJITTER: jitter=303013,
> limit=295400
> May  9 13:30:49 khronos kernel: hardpps: new frequency -434859 >> 5 ==
> -13590
> May  9 13:30:49 khronos kernel: hardpps: new pps.freq=-13589 (add 0)
> May  9 13:31:07 khronos kernel: hardpps: PPSJITTER: jitter=327983,
> limit=4232
> May  9 13:31:21 khronos kernel: hardpps: new frequency -433636 >> 5 ==
> -13552
> May  9 13:31:21 khronos kernel: hardpps: new pps.freq=-13551 (add 38)
> May  9 13:31:37 khronos kernel: hardpps: PPSJITTER: jitter=327881,
> limit=3332
> May  9 13:31:53 khronos kernel: hardpps: new frequency -434615 >> 5 ==
> -13582
> May  9 13:31:53 khronos kernel: hardpps: new pps.freq=-13581 (add -30)
> May  9 13:32:07 khronos kernel: hardpps: PPSJITTER: jitter=323754,
> limit=3620
> May  9 13:32:37 khronos kernel: hardpps: PPSJITTER: jitter=322598,
> limit=4844
> May  9 13:32:57 khronos kernel: hardpps: new frequency -870709 >> 6 ==
> -13605

... to 6

> May  9 13:32:57 khronos kernel: hardpps: new pps.freq=-13604 (add -23)
> May  9 13:33:07 khronos kernel: hardpps: PPSJITTER: jitter=319882,
> limit=5772
> May  9 13:33:37 khronos kernel: hardpps: PPSJITTER: jitter=319118,
> limit=314
> 
> And sometimes it appears:
> 
> May  9 13:27:55 khronos kernel: hardpps: PPSJITTER: jitter=98335,
> limit=14772
> May  9 13:28:07 khronos kernel: hardpps: bad pulse, delta = -794324 ns
> May  9 13:28:08 khronos kernel: hardpps: bad pulse, delta = 769390 ns

A  noise spike (or kernel time problem)...

> May  9 13:28:09 khronos kernel: hardpps: PPSJITTER: jitter=841424,
> limit=177076
> 
> Is this the normal behavour or are the constants frequency changes a
> signal that something could be misconfigured?

What do you guess hardpps does? I thought it would update the frequency drift
to match the PPS signal ;-)

If you've seen enough, just disable debugging messages.

Regards,
Ulrich

> 
> Thanks a lot,
> 
> Christian




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