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Re: [gpsd-users] gpsd time data not present on ntpd

From: Gary E. Miller
Subject: Re: [gpsd-users] gpsd time data not present on ntpd
Date: Sat, 29 Dec 2018 08:32:23 -0800

Yo Massimiliano!

On Sat, 29 Dec 2018 11:23:54 +0100
Massimiliano Fago <address@hidden> wrote:

> I start a gpsd with this command:
> sudo gpsd -D 5 -N -n /dev/ttyAMA0 /dev/pps0

No need for the "-D 5 -N" anymore.  You confirmed that gpsd is working.

> sample NTP0 1546078291.330532005 1546078291.154584005 1546078291.000000000 0 
> -20
> sample NTP1 1546078291.331388005 1546078291.019129005 1546078291.000000000 0 
> -30
> sample NTP2 1546078291.332204005 1546078291.019129005 1546078291.000000000 0 
> -30

I'm not sure how you ended up with SHM(0), SHM(1) and SHM(2).  SHM(1) is

> After that I start ntpd with command:

How did you build ntpd?  Did you build it with all the refclock

It would be helpful to see a log of how you built gpsd and ntpd.

> address@hidden:/home/pi# ntpd

You probably also want '-g' on the command line.

> # Prefer the precise clock at unit 1 over the imprecise one at unit 0.
> refclock shm unit 1 prefer refid PPS

This is using the mysterious SHM(1).  You want unit 2 for the /dev/pps0

> refclock shm unit 0 refid GPS

Best to put this last so that ntpd will not use it.

> # GPS PPS reference
> server prefer
> fudge refid PPS

Now here is the SHM2(20
> # get time from SHM from gpsd; this seems working
> server
> fudge refid GPS

But a duplicate of SHM(0).

> and with ntpmon I see:

Which looks like you forgot to build ntpd with refclock support.  The
build log will explain it.

Gary E. Miller Rellim 109 NW Wilmington Ave., Suite E, Bend, OR 97703
        address@hidden  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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