Re: GPSD Not Using /dev/pps0 But ppstest Shows /dev/pps0 is OK

[Gary E. Miller]

Yo Joshua!

On Wed, 2 Dec 2020 17:51:55 -0500
Joshua Quesenberry <engnfrc@gmail.com> wrote:

> Good call, now that does look more informative! I see some stuff
> about PPS but I'm not sure what to make of it. From the GPS
> datasheet, I did see that PPS is valid on the rising clock edge and
> that the pulse is ~100 ms long.

Notice you only got PPS, before you had a proper fix, then no more.
Lines 1635 to 1640.

gpsd:PROG: KPPS:/dev/pps0 assert  1606948867.424039916, sequence: 14472, clear  
 0.000000000, sequence: 0 - using: assert
gpsd:PROG: KPPS:/dev/pps0 Assert cycle: 1000026, duration:       0 @  
1606948867.424039916
gpsd:PROG: PPS:/dev/pps0 Assert cycle: 1000026, duration:       0 @  
1606948867.424039916
gpsd:PROG: NTP: ntpshm_put(/dev/pps0,-30)  1606948867.000000000 @  
1606948867.424039916
gpsd:INFO: PPS:/dev/pps0 Assert hooks called clock:  1606948867.424039916 real: 
 1606948867.000000000: accepted
gpsd:PROG: PPS:/dev/pps0 Assert accepted @  1606948867.424039916 offset 
-0.424039916

Then nothing.  Needless to say those should be every second.

I have no idea why your PPS in stopped.  With no PPS in, there is
nothing gpsd can do.  gpsd is just a passive consumer.  Something else
killed your PPS.

> The log says missing PPS_CAPTURECLEAR...

Yes, that is a longstanding bug in the pps-gpio driver.  Not a problem,
as long as you have the proper edge.  Which you do, as long as there are
no inversions in the path.

> do I need to provide other options beyond:
> `dtoverlay=pps-gpio,gpiopin=6`?

Nope.  Not for the kernel.

> There's a blurb about chrony not
> being active, but hopefully that's not needed to get the PPS pulse
> working in GPSD and a time offset?

gpsd feeds chronyd.  gpsd does not care if chronyd is running.  But ntpd
and chronyd need gpsd to be accurate.

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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