[ntp:questions] Pi 4 and Ultimate hat weirdness

Gary E. Miller gem at rellim.com
Tue Jan 26 18:55:43 UTC 2021


Yo Jim!

On Mon, 25 Jan 2021 14:04:58 -0800
Jim Pennino <jimp at gonzo.specsol.net> wrote:

> > What versions of gpsd and xgps?  
> 
> gpsd -V
> gpsd: 3.17 (revision 3.17)

3.17 is from 2017.  More than a few bugs and improvements since then.

> ntpd --version
> ntpd 4.2.8p12 at 1.3728-o (1)

We prefer NTPsec, our sister project here, but that s/b OK.

> > From your distro of from source?  
> 
> Distro, totally up to date.

You may be up to date with your distro, but your distro is not up to 
date with gpsd.

> > Did xgps give any warnings on the command line when started from the
> > command line?  
> 
> xgps
> Gtk-Message: 13:45:00.966: Failed to load module "canberra-gtk-module"
> TypeError: Couldn't find foreign struct converter for 'cairo.Context'

That is easy.  You are missing at least one python dependency.  That
is a bug you need to report to your distro as your package manager should
have dealt with that.

> Makes me think the distro is missing a dependancy.

Yup.

If you look in the gpsd INSTALL file for you distro it might tell
you the missing giles.   Here is what it says for Buster:

--------------------------------------------------------------
# apt-get install python-gi-dev python-cairo-dev
# apt-get install python-gobject-2-dev libgtk-3-dev
--------------------------------------------------------------

> > > I don't care too much about this one as AFAIK xgps is broken on
> > > Pi.  
> > 
> > Nope.  Works for me.  
> 
> On buster?

Yes, but from source, not from a package.

> > > Second weird thing; I started the 20 driver in mode 0. ntpq showed
> > > lots of syntax errors on the $GPGGA message.  
> > 
> > Before that:
> > 
> > How are you running gpsd?  Root?  With what command line?  
> 
> sudo systemctl start gpsd
> sudo systemctl start gpsd.socket

Oh.  systemd(umb).  I'm not allowed to help people with systemd(umbest).

But not your problem, yet.

> ps -eo euser,egroup,args | grep gps
> gpsd     dialout  /usr/sbin/gpsd -n -r /dev/ttyAMA0 /dev/pps0

Good, you have the -n and the pps0.  Commonly missed requirements.

> ps -eo euser,egroup,args | grep ntp
> ntp      ntp      /usr/sbin/ntpd -p /var/run/ntpd.pid -g -u 115:124

You may want to add -N and -g.

> > Then please copy the errors here.
> >   
> > > I changed the mode to 29 to deselect $GPGGA; no errors from ntpq.
> > > So maybe it was a satellite thing, but whatever it was, no more
> > > errors.  
> > 
> > We can only guess without seeing what you see.  
> 
> Not a big deal to me if ignoring $GPGGA makes the errors go away.

Another guess, without data.

> The GPS has been powered up since I stuck in the battery for the
> on board RTC 5+ days ago.
> 
> How long does it typically take a receiver to have the current leap
> second.

Certainly no longer than 30 minutes after a fix.

Slow serial port speed can also cause your problem.  Be sure you are
running at 9600, or faster.  Faster the better.

> BTW, the GPS has an external antenna with a good view of the sky
> and cgps alway shows 11+ satellites in view and always 8+ in use.

Good.  Also important that they have good SNR.

> > > Also the jitter times look high. At this moment ntpq shows:  
> > 
> > That is to be expected early on.  Don't bother to look at the
> > jitter until the offset is stable for hours.  
> 
> Right now ntp has been running for about 18 hours.

It can take weeks.  On a lightly loaded system.  If you are running a
lot of daemones it may never improve.

Setup ntpviz.  That makes monitoring the system mmuch easier.

> > > For comparison, a GlobalSat BU-353-S4 USB GPS on a PC ubuntu
> > > system shows: *SHM(0)          .SHM.            0 l    3   16
> > > 377    0.000 -0.728   1.356  
> > 
> > Which I assume had been running for months.  
> 
> Yes and no; the system was rebooted 4 days before.

But the adjtime file survives a reboot.  And not as good as your current
PPS.

The 0.720 you see now is a start.  Now you have to check for anything that
disturbs your CPU.  Heavy loads, temperature swings, CPU speed changing, etc.

RGDS
GARY
---------------------------------------------------------------------------
Gary E. Miller Rellim 109 NW Wilmington Ave., Suite E, Bend, OR 97703
	gem at 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
-------------- next part --------------
A non-text attachment was scrubbed...
Name: not available
Type: application/pgp-signature
Size: 851 bytes
Desc: OpenPGP digital signature
URL: <http://lists.ntp.org/pipermail/questions/attachments/20210126/6c858621/attachment.sig>


More information about the questions mailing list