unruh wrote:
On 2011-07-15, David Lord <sn...@lordynet.org> wrote:
Michael Eder wrote:
Again we are talking effectively what happens. There is a good deal of
logic what to do if the NMEA and/or pps does not come in and if the system
clock is significantly different from either the NMEA or pps. A whole day
on the lab bench with a scope on both the pps and the NMEA these never
happen. The pps comes in and by definition it must be represent the second
+ 1 of the previous NMEA string. This is exactly the same logic that gpsd
uses and is why we tell NTP that the NMEA has an offset.
We scope the oscillator also and it is a very expensive oceanographic device
that adjusts for temperature automatically.
Sounds like a common problem and I note when we add an additional network
clock the problem seems to go away.
I note there are multiple SHM segments in NTP. Anyone tried writing the pps
time into two locations to fix this problem?
Did you try my suggestion of marking the NMEA as prefer rather
than the PPS?
server 127.127.28.0 minpoll 4 maxpoll 4 prefer
fudge 127.127.28.0 time1 0.680 refid NMEA
server 127.127.28.1 minpoll 4 maxpoll 4
fudge 127.127.28.1 refid PPS
instead of:
server 127.127.28.0 minpoll 4 maxpoll 4
fudge 127.127.28.0 time1 0.680 refid NMEA
server 127.127.28.1 minpoll 4 maxpoll 4 prefer
fudge 127.127.28.1 refid PPS
What are you feeding the shm with? Ie, what are you putting into the
shm How do you deterime the "seconds" for the PPS?
I would also make sure that the system did not think that nmea was a
stratum 0 server, but jack its stratum up, so the system always thought
that the PPS was a higher stratum than nmea.
I am not sure why you would make nmea a preferred source?
When I tried when I was using only a single source and normal
type 20 NMEA driver it was needed otherwise ntpd doesn't sync.
Having the type 22 PPS driver as prefer gave the same bad
results as posted by the OP.
I've been told my config is wrong but my server hasn't had
any problems (although once it was setup with the new GPS
there have been other servers added).
<http://www.lordynet.org.uk/mrtg/stats/ntp/me6000_ntp.html>
David
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