Re: gpsd + chrony + pps

[Stéphane Péneau]

Hi Gary!

Le 19/06/2020 à 18:32, Gary E. Miller a écrit :

> Yo Stéphane!
>
> On Fri, 19 Jun 2020 15:36:36 +0200
> Stéphane Péneau <stephane.peneau@wanadoo.fr> wrote:
>
> > gpsd:
> >
> > DEVICES="/dev/ttyS1 /dev/pps0"
> > # Other options you want to pass to gpsd
> > GPSD_OPTIONS="-n -b -s 115200"
> > # Automatically hot add/remove USB GPS devices via gpsdctl
> > USBAUTO="false"
> >       
> I have no idea what the above refers to, it is not part of gpsd.
>     
    It's the /etc/default/gpsd file used by ... a
    systhingemd I won't name... ;-)
> I need to know how gpsd is running, as root:
>         # pstree -paul | fgrep gpsd
>         # netstat -apn | fgrep 2947
>     
    root@orangepizero:~# pstree -paul | fgrep gpsd
      |-gpsd,3779,gpsd -n -b -s 115200 /dev/ttyS1 /dev/pps0
      |   |-{gpsd},3786
      |   `-{gpsd},3787
      |   |       |           |-grep,13953 -F gpsd

root@orangepizero:~# netstat -apn | fgrep 2947
tcp        0      0 127.0.0.1:2947          0.0.0.0:*               LISTEN      1/init
tcp6       0      0 ::1:2947                :::*                    LISTEN      1/init

> > chrony.conf:
> >
> > refclock SHM 0 refid GNSS precision 1e-1 offset 0.150 delay 0.2
> > noselect refclock SOCK /var/run/chrony.ttyS1.sock refid PPS2 lock GNSS
> >       
> Why SHM and SOCK?  They reference the same source (NMEA serial) and have
> the same data.  That is an either/or.  Why are you locking a signal to
> itself?  I cleaned up the doc last night to make that clearer.
>

Maybe because it was like that in the documentation:

https://gitlab.com/gpsd/gpsd/-/blob/cb2ca370500c7002c30b185d2b84f117436e86d7/www/gpsd-time-service-howto.adoc#L980

Let's forget this

> Check out the doc as it stands today.
>

Yes, it' clearer now, but is a 0.9999 offset not a little high value ?
https://gitlab.com/gpsd/gpsd/-/blob/master/www/gpsd-time-service-howto.adoc#L954

This is my new tests, following the new doc

With:

refclock SOCK /var/run/chrony.ttyS1.sock refid GNSS precision 1e-1 offset 0.150 delay 0.2
refclock SOCK /var/run/chrony.pps0.sock refid PPS precision 1e-7

I get:

MS Name/IP address         Stratum Poll Reach LastRx Last sample
===============================================================================
#? GNSS                          0   4     0     -     +0ns[   +0ns] +/-    0ns
#* PPS                           0   4   377    17   +971ns[+1421ns] +/- 1571ns

# ...

No data with chrony.ttyS1.sock but chrony.pps0.sock is ok.

    Stf