[time-nuts] GPSDO and holdover

Paul tic-toc at bodosom.net
Fri Apr 25 14:20:57 EDT 2014

On Tue, Apr 22, 2014 at 9:57 PM, Tom Van Baak <tvb at leapsecond.com> wrote:

> I have noticed skipped 1PPS on the Adafruit GPS also.

I've always assumed this could happen but as a result of RF signal loss not
a glitch in the gps.  So I've started recording event timestamp deltas
using the Linux kernel PPS interface.  I read assert events (e.g.
1398449188.001000242#1741672) and compute  timestamp and event deltas.  If
the t delta is < .9 something horrible must have happened and if it's > 1
some didn't happen assuming the event count delta is always 1.

I wonder if this is a reasonable approach or if I'm being lazily
optimistic.  I just started (and I haven't added a join with the valid fix
indicator yet) but I've had two missing pulses in the last 24 hours.

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