Re: [gpsd-dev] U-Blox M8, PPS and NTPsec - GPSd logic enhancement

[Gary E. Miller]

Yo Martin!

On Fri, 5 Apr 2019 13:34:16 -0400
Martin Boissonneault <address@hidden> wrote:

> >>     From what I observed, sometimes GPSd seems to associate the
> >> PPS to the wrong timestamp and that would  confuse NTPd.  
> > Now that is unusual.  At least native gpsd.  As long as your RasPi
> > has other network chimers that should never happen.  It can happen
> > when you have a voltage mismatch on PPS line, or large CPU load.  
> 
>    It just happened on restart of both GPSd and NTPsec. After a
> while, it corrected itself without intervention.

Consistent with what I said to fix in your ntp.conf.

> I will disable the unused messages TIM-TP, NAV-TIMExx in the mean
> time...

I would not bother.  At 115,200 you have more than enough bandwidth.

> --ntpmon while 1s off:
>       remote           refid      st t when poll reach delay
> offset jitter
>   SHM(1)          .gPPS.           0 l    -    1    0   0.0000
> 0.0000 0.0010
> *SHM(2)          .gPPS.           0 l    -    1  377   0.0000
> 1000.006 0.0001

Yeah, bad placement in the ntp.conf.  Also, poll of 1 is not good.

And where is NTP2 coming from?  You never mentioned that before.

> --ntp.conf extract:

Which of course destroyed the context.

> # GPS PPS reference (GNSS PPS), only one of two will be present.
> refclock shm unit 1 refid gPPS minpoll 0 maxpoll 8 prefer
> refclock shm unit 2 refid gPPS minpoll 0 maxpoll 8 prefer

Put these at the bottom, with a reasonable poll.  minpoll 0 is
not reasonable.

> # Government NTP reference servers - Stratum 2:
> server time.nrc.ca iburst prefer
> server time.chu.nrc.ca iburst prefer

You surely do not want to prefer chimers that are far away.

RGDS
GARY
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Gary E. Miller Rellim 109 NW Wilmington Ave., Suite E, Bend, OR 97703
        address@hidden  Tel:+1 541 382 8588

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