Re: gpsd + chrony + pps

[Gary E. Miller]

Yo Stéphane!

On Sat, 20 Jun 2020 15:29:17 +0200
Stéphane Péneau <stephane.peneau@wanadoo.fr> wrote:

> > 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

Do you have magic-hat compiled in?  It is default on Linux, and makes the
/dev/pps0 redundant.

> 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

I already knew about that weirdness.  No comment.

> Maybe because it was like that in the documentation:

Was.  Fixed.  Right?

> > Check out the doc as it stands today.  
> 
> Yes, it' clearer now, but is a 0.9999 offset not a little high value ?

Depends.  At NMEA standard speed of 4800bps that was required.  YMMV.
By being (about) an even second it was supposed easier to calculate in
your head.  Does not matter if you go noselect.  May matter a lot if
you do not.

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

No noselect.  Either the high offset or noselect or you will have problems.

> refclock SOCK /var/run/chrony.pps0.sock refid PPS precision 1e-7

I don't use the sock interface, it is only for chronyd, which I do not use.

> #? GNSS                          0   4     0     -     +0ns[ +0ns] 
> +/-    0ns
> #* PPS                           0   4   377    17 +971ns[+1421ns]
> +/- 1571ns
> # ...

That is weird.  Are sure chronyd is started well before gpsd?

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

Which is what you need, the ttyS1 is nice, but dangerous.

Can you confirm the sock files that gpsd is trying to open?

I don't have a sock file, so this fails, but it shows you the file
that gets opened:

# gpsd -nGND 6 /dev/ttyACM1 |& fgrep sock
gpsd:IO: opening IPv4 socket
gpsd:IO: opening IPv6 socket
gpsd:PROG: PPS:/dev/ttyACM1 chrony socket /run/chrony.ttyACM1.sock doesn't exist

What does yous look like?

RGDS
GARY
---------------------------------------------------------------------------
Gary E. Miller Rellim 109 NW Wilmington Ave., Suite E, Bend, OR 97703
        gem@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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