Re: Clarifications about PPS SHM content

[Martin Boissonneault]

Hi!

Update : It's not the ADS-B stuff, not the graphing, the Pi has nothing running 
but NTPsec, GPSd and rrd stats gathering (but Graphs1090 is stopped). Still 
~1uS jitter. Used to be ~275nS!

Anybody using a RasPi 3B+ on Buster, up to date, having similar issues? Note: 
GPSd is 3.20 compiled from tarball, NTPsec 1.1.8 too, as the repo pkg are older.

I'm about to get a new Pi 4B if I can't figure it out...

For the moment, I reactivated everything ADS-B and graphing. Can't make it much 
worse!

Good night everyone,

Martin Boissonneault
Sent from my phone

> On Apr 3, 2020, at 22:34, Gary E. Miller <address@hidden> wrote:
> 
> Yo Martin!
> 
>> On Fri, 3 Apr 2020 12:15:15 -0400
>> Martin Boissonneault <address@hidden> wrote:
>> 
>> Just a quick update: _My jitter wasn't caused by ntpheat._
>> For the past few days, I turned off ntpheat and this bad ~700ns
>> jitter (had ~265ns before) is continuing. I've been hunting the
>> cause, the clue I have is a negative clock offset spike every 45min.
> 
> Chasing ns is harder than it looks.
> 
>> So far, I think it's the timeout period of the ADS-B decoders
>> (~3888s). My current hypothesis is that there are so few planes up
>> there that the feeders/decoders restart because they haven't seen a
>> plane in 45min. So, I've shut down the ADS-B decoders/feeders.
> 
> I'm unfamiliar with how dump978 and dump1090 do their thing...
> 
>> If I'm right, I'll know in a few hours! Then, if it's fixed, I'll be 
>> able to brag about my NTP server being affected by COVID-19 ;-)
> 
> Fingers crossed.
> 
> 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?
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