refclock 28 gone wacky on me

Frank Nicholas frank at
Fri Jun 10 11:47:11 UTC 2016

> On Jun 9, 2016, at 9:58 PM, Eric S. Raymond <esr at> wrote:
> Frank Nicholas <frank at>:
>> I can tell you from experience, that with the Adafruit hat, and the default sentences, 9600 baud is not fast enough.  Some periodic sentences (period > few seconds) will push a cycle past one (1) second.  Even when used with PPS, eventually it will eventually be marked as a false ticker.
> That's odd.  The normal semtence budget including GPGSV should fit inside a
> second.  Are you getting some kind of $PMTK thing that pushes it over?

It’s been a while (years), and at the time it was pure NTP (no gpsd involved).  Whatever the sentences were that were pushing it over didn’t happen very close together.  I seem to remember that one was reporting if it was using the external vs. internal antenna and that would probably have been a $PMTK sentence.  I was using an external antenna.  When I use it with gpsd, is gpsd “aware” of that chipset and turning some sentences off ($PMTK)?


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