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

[Gary E. Miller]

Yo Martin!

On Fri, 5 Apr 2019 18:52:23 -0400
Martin Boissonneault <address@hidden> wrote:

> > So: what is your current ntp.conf,  
[...]
> # LAN servers:
> server 192.168.10.10 iburst maxpoll 5
> server 192.168.10.11 iburst maxpoll 5 prefer

You should not prefer a LAN server when you have local PPS.

> # GPS PPS reference (Only one 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
> refclock shm unit 1 refid gPPS prefer
> refclock shm unit 2 refid gPPS prefer

Don't duplicate the refid.

Once again, you have still not said where SHM(1) and SHM(2) come from.

> # GPS Serial data reference (NTP0)
> #refclock shm unit 0 refid GNSS flag1 0 time1 0.0 minpoll 0 maxpoll 8 
> stratum 10 noselect
> #refclock shm unit 0 refid GNSS flag1 0 time1 0.025 minpoll 0 maxpoll
> 8 stratum 10 noselect
> # stratum 10

Why is this commented out?  You need SHM(0) to get the right second
for PPS.

> > what is conencted to SHM(2) and SHM(2)?  
> Both SHM(1) and SHM(2) are from GPSd.

Obviously, but what is gpsd configured to send as SHM(1) and SHM(2)?
And what happend to SHM(0)?  Very strange configuration.

> They are the SHM related to the 
> GNSS PPS from the offsets I see. Both are the same PPS from the GNSS 
> attached.

You have two PPS sources?  What does that look like on your gpsd command
line?

> Only one shows up, usually SHM(2).

"usually" is not a good thing.  That shows a major problem.  Fix that
before continuing.

> I also have SHM(0) from GPSd, and that one jumps ~100ms every 45 
> minutes. I assume SHM(0) is from the serial messages. It's disabled.

Don't disable that.  You need that to provide the proper second for the
PPS.  Just "noselect" it.

> >> I found that
> >> adding NAV-TIMEGPS was fixing the 1 second offset. I've tried it
> >> many times, and disabling NAV-TIMEGPS and stop/start GPSd gets
> >> SHM(2) off by one second. Enabling back the message and stop/start
> >> GPSd and time is good! Odd...  
> > All you are doing is moving the sentences around.  That can be good
> > or bad as it affects the parser trying to unroll things.  
> Just trying to get it not marked as a falseticker :-/

Uh, completely different levels.  Before you try weird configurations
you need to get the baseline configuration working.  Reset your GPS
to what gpsd expects.

> > And how did you set that configuration?  With gpsctl, or ubxtool,
> > defaults, or?  
> 
> I configured the u-Blox M8 manually using u-Center on Windows. I 
> monitored the output from cgps while doing so to see if the message
> was decoded or not and how GPSd reacted to it.

Ugh.  An unmaintainable configuration.  Use gpsctl or ubxtool
to set standard messages.  Better yet, don't touch the defaults.

> When GPSd was first installed, it was disabling Galileo and Glonass 
> after a while. I now use a jumper to prevent GPSd from reconfiguring
> the GNSS.

Uh, that is not gpsd changing your constellations.  To prevent gpsd from
touching your GPS just use the -b command line switch.  But then you got
gpsd all confused.

Once again, gpsd did not do that, but you really do not want to use
Galileo and Glonass when doing timing.  So says the offical u-blox
doc.

> To change the configuration, I connect my serial-USB
> adapter and change what I want with u-Center. GPSd can't modify my
> settings without me putting the jumper back. I'm just trying to keep
> the minimum messages while having Galileo and Glonass active.

Which is wrong on many levels.  Don't fight gpsd doing the right thing.

> > That is certainly not what gpsd expects, and thus
> > untested and likely suboptimal.  
> 
> OK, then I must ask what does GPSd expect?

I guess you keep missing the part where I say to set your GPS with
gpsctl or ubxtool.

> > We can't really support configurations that are not well tested
> > and part of our regressions.  
> I don't mind giving full GNSS control back to GPSd, but then, why was
> it disabling Galileo and Glonass?

No, it was not.  And anyway that is the right thing to do.

See driver_ubx.c lines 1770+ to see what gpsd does.

> > Too early to look at ntpmon, your pool servers not running yet.  
> 
> Well, they where up, and after a while, they where released. NTPd
> picks the best and drops the unneeded extras?

No.

> SHM(1)          .gPPS.           0 l  64    0 0ns      0ns    954ns

Why is SHM(1) broken?

RGDS
GARY
---------------------------------------------------------------------------
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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