[rc-oncore] [Bug 2872] Oncore is offset by current GPS-UTC delta at startup

bugzilla-daemon at ntp.org bugzilla-daemon at ntp.org
Thu Aug 20 08:28:05 UTC 2015


http://bugs.ntp.org/show_bug.cgi?id=2872

Martin Burnicki <burnicki at ntp.org> changed:

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

--- Comment #1 from Martin Burnicki <burnicki at ntp.org> 2015-08-20 08:28:05 UTC ---
GPS receivers only know the current UTC to GPS time offset immediately after
power-up if they save the latest UTC parameter set received from the satellites
in a non-volatile memory while powered off.

If this isn't supported, or the backup battery on the GPS receiver is faulty,
the receiver has to wait until the UTC parameter set is broadcasted by the
satellites. This can take about 12 minutes since this kind of information is
sent repeatedly by the satellites at this interval.

If the availability of the UTC parameters (or the offset number of seconds) can
be decoded from some field in the NMEA sentences then this could be used to let
the driver reject the GPS time source until the data is available.

However, I'm not familiar with the details sent by the NMEA sentences, so I
can't tell if this is possible.

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