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Re: gpsd + chrony + pps

From: Stéphane Péneau
Subject: Re: gpsd + chrony + pps
Date: Sat, 20 Jun 2020 15:29:17 +0200
User-agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:68.0) Gecko/20100101 Thunderbird/68.9.0

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 <> wrote:


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
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*               LISTEN      1/init
tcp6       0      0 ::1:2947                :::*                    LISTEN      1/init


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:

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 ?

This is my new tests, following the new doc

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.


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