Gary E. Miller <g...@rellim.com>: > > It sounds like this has implications for how I should write the HOWTO > > recipe. Are you saying that with refclock 20 the source can get > > marked as a falseticker if it loses PPS for a while? > > Yup. Easy to test, just disconnect the PPS signal, if the #20 acts > like the #48, it will start tracking the NMEA time, which will be offset > and jittery. When the PPS returns ntpd will rule out that clock due to > the high jitter. Eventually it sorts itself out, as long as the GPS > stays locked.
Well, shit. That's a strong argument for deprecating #20 and eventually
shooting it through the head. Hal, I hope you're paying attention to this.
> I'm busy today, but I'll run some tests later to verify that is the
> current behavior. At a minimum #2 makes it very hhard to see the NMEA
> time and fix a good offset.
Please do that.
> Last I looked at #48 it was bad in the default configuration due to the
> same NMEA/PPS mashing.
>
> > If that's so, then maybe we do want to base the build on refclock 28
> > and what you call gpsd-lite.
>
> With the QNX thing, I wonder how portable #28 is. Maybe the thing to do is
> fix #48 or #20. But I fear we'll start Yack Shearing.
OK, this is a policy call. I just checked with Mark on IRC and he concurs.
QNX is firmly out of scope. We'll handle it later if there is demand
and resources backing the demand.
We *will* assume POSIX-compliant shared memory on our target systems.
My intention is to officially deprecate refclocks 20 and 48 in favor
of 28 (SHM), explaining that the way 1PPS and in-band information is
mingled produces bad behavior on 1PPS dropouts. Actual deprecation will
wait on confirmation from Gary's tests.
The HOWTO will be rewritten to use a stripped gpsd-lite version feeding
SHM.
Thanks for bashing your way through this, Frank and Gary. You've
clarified several murky issues.
--
<a href="http://www.catb.org/~esr/";>Eric S. Raymond</a>
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