ntpsec is ignoring PPS

Gary E. Miller gem at rellim.com
Tue Nov 30 20:53:55 UTC 2021

Yo folkert!

On Tue, 30 Nov 2021 20:48:11 +0100
folkert via users <users at ntpsec.org> wrote:

> > > 	server minpoll 1 maxpoll 4 prefer
> > > 	server minpoll 1 maxpoll 4 prefer  
> > 
> > You have 2 PPS?  Odd.  
> To compare their results as one is a false-ticker according to ntp.

ntpd cant determine falseticker with only 2 chimers.  So it flipped a
coin.  But it uses neither since minsane not fulfilled.

> > minpoll 1 is too small.  minpoll 3 o4 4 is better.  
> Ok, changed that.

You need to run for days, and watch ntpviz, to find the best value.

> > > 	pool nl.pool.ntp.org  
> > If you look below, you see this is not working.  It should put 4
> > pool servers into your chimers.  
> Sorry I did not paste everything:

Well, that really changes things:

*ntp0.bgwlan.nl  .PPS.            1 u   14   64  377  23.6166   1.5371   0.8806

When debugging, your problem is usually in the place you snip out.

ntpd chose that as the most accurate source.  Notice the offset and jitter
between that, and your PPS1 and PPS2 are very small.  So a reasonable choice
for ntpd to make at startup.  You need to let it settle, for days, before
the local PPS are obviously better than a remote one.

So, let it run, and set up ntpviz, check the graphs on Friday.  Until
then, have a beer.

> > That is doing things the hard way.  
> root at gpsdomonitor:~# ppstest /dev/pps0

Looks good.

> > You prolly should of led with that.  The garmin is old and you can
> > get way better receivers now for under $20.  But, as you showed,
> > they are working as expected.  
> Some more details: this is not the only with a gps connected. This is,
> though, the only one with a gpsdo connected (and that garmin as
> reference).

And the shitty Garmin is still in the loop.

> I'm trying to debug what is wrong with the gpsdo and/or
> ntp.

Nothing is wrong that I can see, expcept you need patience.  Days of
patience, for your clocks to get settled.  Once the driftfile has good
data, then startup will be faster.  Controlling the room temperature
also helps a lot long term.

> The gpsdo only feeds a 1PPS to the pi, so I can't go the gpsd way

You can.  I have,  But it does complicate things.  Get this stable

> > You need to carefullly read and understand this part:
> > https://gpsd.io/gpsd-time-service-howto.html#_feeding_ntpd_from_gpsd
> >  
> I know that text. I should've kept the pool-part for clarity.

Clarity?  No, the exact opposite of clarity, you hid your problem.

Gary E. Miller Rellim 109 NW Wilmington Ave., Suite E, Bend, OR 97703
	gem at rellim.com  Tel:+1 541 382 8588

	    Veritas liberabit vos. -- Quid est veritas?
    "If you can't measure it, you can't improve it." - Lord Kelvin
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