[rc-oncore] [Bug 2610] Oncore refclock ignores second fractions from GPS

bugzilla-daemon at ntp.org bugzilla-daemon at ntp.org
Sun Dec 6 22:21:58 UTC 2015


https://bugs.ntp.org/show_bug.cgi?id=2610

Juergen Perlinger <perlinger at ntp.org> changed:

           What    |Removed                     |Added
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                 CC|                            |perlinger at ntp.org

--- Comment #13 from Juergen Perlinger <perlinger at ntp.org> 2015-12-06 22:21:58 UTC ---
This looks like a timing problem to me: If the oncore data is written very late
in a second, there's a chance that the next PPS edge arrives before the
sentence is decoded -- and then the time stamp from the message is mapped to
the wrong PPS time stamp. Hence Chris' observation of being too late by one
second.

My experience is limited to the serial NMEA driver, but there exists a similar
problem with some modules.

If the oncore system is expected to output the @@Ha data at the full second,
then Chris' device is just a bit early, and rounding to the closest second
based on the fraction should provide the right time stamp value. If the oncore
data output timing is unrelated to the PPS cycle, all bets are off.

Don't know if this is a helpful comment -- but the symptom looks somewhat
familiar to me.

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