[ntp:questions] Kernel PPS with Debian

Steve Kostecke kostecke at psp2.ntp.org
Thu Nov 3 17:27:26 UTC 2011


Forwarding to see if removing base64 encoding affects propagation.

On 2011-11-03, Dave Hart <hart at ntp.org> wrote:
> On Thu, Nov 3, 2011 at 01:16, jimmyterrence <jimmyterrence at gmail.com> wrote:
>> It only ever notices the NMEA output in ntp, and I can tell that
>> because the jitter is always terrible:
>>
>> ?? ?? remote refid st t when poll reach delay offset jitter
>> ========================================
>> *GPS_NMEA(0) .GPS. ??0 l ??7 16 377 0.000 23.791 ??16.842
>>
>> It doesn't seem to matter how long I let ntp run, it never seems to
>> see the PPS signal.
>>
>> Right now, my ntp.conf entry is the following:
>>
>> server 127.127.20.0 minpoll 4 maxpoll 4 mode 0 prefer
>> fudge 127.127.20.0 flag1 1 flag2 0 time2 0.600
>>
>> I've tried ntp-4.2.6.p3 (came with Debian Wheezy) 4.2.6p4 and 4.2.6p5-
>> RC1 from ntp.org
>>
>> What do I need to do to get ntp to notice the PPS signal? What am I
>> missing?
>
> My guess is your ntpd binaries were built without PPSAPI support,
> because (or the builder in the case of the stock one) you don't have
> timepps.h available where ntpd can find it.  You can verify that for
> the 4.2.6p5-RC1 you built by searching for PPS in its config.h:
>
> /* Do we have the PPS API per the Draft RFC? */
> #define HAVE_PPSAPI 1
> #define HAVE_SYS_TIMEPPS_H 1
> /* #undef HAVE_TIMEPPS_H */
>
> If you see /* #undef HAVE_PPSAPI */ you need to either pick up
> timepps.h by hand somewhere, or possibly update your libc.  Linux has
> a strange convention of distributing kernel-dependent headers in libc,
> so building a kernel with PPSAPI support doesn't necessarily imply you
> have the right headers to match.
>
> If you do see HAVE_PPSAPI defined, check your syslog for messages from
> ntpd including the text "time_pps".
>
> Good luck,
> Dave Hart



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