Re: NTPsec reports excessive jitter from GPSD/KPPS SHM

[Gary E. Miller]

Yo Nick!

On Wed, 04 Mar 2020 22:17:25 +0000
"Nick Burkitt" <address@hidden> wrote:

> It's not clear if this is a GPSD question, or an NTPsec question, but
> I have to start somewhere. :-)

This is a good place.

> No doubt I've got something configured wrong.

Or prgrammed something wrong.

> use-gpsd-shm:

Not too bad.  What about the other includes?

> root@MPM-4006:~# ppstest /dev/pps0
> trying PPS source "/dev/pps0"
> found PPS source "/dev/pps0"
> ok, found 1 source(s), now start fetching data...
> source 0 - assert 1583357777.950557839, sequence: 15337 - clear  
> 0.000000000, sequence: 0

Why is your clear broken?  Raspberry Pi driver?

> source 0 - assert 1583357778.950736721, sequence: 15338 - clear  
> 0.000000000, sequence: 0

Note the consistent 50 ms offset.

> Representative ntpmon output (afterPPS is marked as a falseticker):

Corrupted ntpmon output.  Missing offset and jitter.  The important parts!

> Representative gpsmon output:

gpsmon is not really maintained.  Use cgps or xxgps instead.

> PPS driver code:
> 
> static irqreturn_t core100_pps_handler( int irq, void* data )

Uh, hold on.  This is not gpsd or NTPsec code.  Maybe you should have
led with the fact you are using strange code?  Where did this come
from?

Pending confirmation with a clean and uncorrupted ntpmon output, it looks
to me like you are measureing the wrong PPS edge.

RGDS
GARY
---------------------------------------------------------------------------
Gary E. Miller Rellim 109 NW Wilmington Ave., Suite E, Bend, OR 97703
        address@hidden  Tel:+1 541 382 8588

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