[time-nuts] Raspberry Pi NTP server
Tim Shoppa
tshoppa at gmail.com
Sun Jul 5 15:14:55 UTC 2020
Andrew, outlier rejection in NTPD is not the most stable thing in the world.
You have two local refclocks that are consistently 200ms off from the "rest
of the world" and this is 10 times larger than the round trip delay to the
rest of the world.
But the local stratum 0 refclock poll interval is ten or twenty times more
frequent than the rest of the world so the local wrong clock gets to
trigger the algorithm ten times as often as the rest of the world.
The outlier rejection NTPD algorithm goes absolutely bonkers in this case.
Which is good because you see it and fix the actual problem.
Like David suggested, seeing the 200ms offset, this 200ms is a very common
default PPS pulse width so it almost certainly is triggering off the wrong
edge.
Tim N3QE
On Sun, Jul 5, 2020 at 7:50 AM Andrew Hancock <
andrew.hancock at cyrus-consultants.co.uk> wrote:
> Thanks David
>
> I may try that list.
>
> It is odd, it works fine, and then craps out....
>
> And then it's happy again...
>
> Andrew
>
> -----Original Message-----
> From: time-nuts <time-nuts-bounces at lists.febo.com> On Behalf Of David J
> Taylor via time-nuts
> Sent: 03 July 2020 18:34
> To: time-nuts at lists.febo.com
> Cc: David J Taylor <david-taylor at blueyonder.co.uk>
> Subject: Re: [time-nuts] Raspberry Pi NTP server
>
> A puzzle (so I hope) I'm in the correct place.
>
> I've built myself, many years ago an NTP server, on a RPi 1, which not
> sure if ever ran properly.
>
> It uses a u-blox6 board, connected to the Pi correctly, and PPS to GPIO,
> compiled NTP to include kernel PPS support.
>
> GPS 3D fix is fine, using an outside aerial, there are no issues here
> reported with cgps -s or gpsmon, but recently I've racked mounted all my
> PIs in a network rack.
>
> So I cannot use HaTs anymore, so I cobbled together a GPS ublox6 (same
> module) but using a FT232RL, and connected all the pins correctly, and DCD
> so I can get PPS.
>
> Cgps -s and gpsmon, reports all is well, pps registers correctly...
>
> But here's the weird thing, it starts out okay, from what I can tell, and
> I get 377 for both GPSD and PPS
>
> remote refid st t when poll reach delay offset
> jitter
>
> ==============================================================================
> *127.127.28.0 .GPSD. 1 l 21 32 37 0.000 98.447
> 89.508
> o127.127.22.0 .PPS. 0 l 20 32 17 0.000 -63.468
> 27.800
> uk.pool.ntp.org .POOL. 16 p - 1024 0 0.000 0.000
> 0.004
> +212.23.8.6 195.66.241.2 2 u 129 1024 1 13.266 198.007
> 3.273
> +212.23.10.129 85.199.214.99 2 u 134 1024 1 19.693 195.605
> 3.282
> +178.62.18.76 85.199.214.100 2 u 135 1024 1 13.804 195.465
> 3.299
> +185.120.34.123 85.199.214.98 2 u 130 1024 1 12.808 197.879
> 3.304
> +51.68.198.213 85.199.214.102 2 u 132 1024 1 13.534 197.377
> 3.402
> +95.215.175.2 178.79.160.57 3 u 131 1024 1 19.722 198.984
> 3.244
>
> And then later.
>
> remote refid st t when poll reach delay offset
> jitter
>
> ==============================================================================
> *127.127.28.0 .GPSD. 1 l 20 32 377 0.000 -38.512
> 43.162
> x127.127.22.0 .PPS. 0 l 19 32 377 0.000 -159.01
> 0.949
> uk.pool.ntp.org .POOL. 16 p - 1024 0 0.000 0.000
> 0.004
> +212.23.8.6 195.66.241.2 2 u 255 1024 1 13.615 142.618
> 1.953
> +212.23.10.129 85.199.214.99 2 u 261 1024 1 19.799 144.028
> 3.384
> +162.159.200.123 10.63.8.8 3 u 258 1024 1 18.501 141.995
> 3.016
> +185.53.93.157 81.187.26.174 2 u 258 1024 1 15.385 143.600
> 3.045
> -217.114.59.3 33.117.170.50 2 u 259 1024 1 19.927 143.014
> 3.364
> +109.74.192.97 85.199.214.99 2 u 255 1024 1 13.578 142.723
> 1.864
>
> Which does not look good, notice the x in front of PPS...
>
> And then sometimes.... It borks.. and drops out completely and * and x
> disappear, and all the +.
>
> Then go back to
>
>
> remote refid st t when poll reach delay offset
> jitter
>
> ==============================================================================
> *127.127.28.0 .GPSD. 1 l 27 64 3 0.000 34.096
> 1.954
> o127.127.22.0 .PPS. 0 l 26 32 3 0.000 -69.865
> 14.194
> uk.pool.ntp.org .POOL. 16 p - 1024 0 0.000 0.000
> 0.002
> 212.23.8.6 195.66.241.2 2 u 121 1024 1 13.316 200.644
> 0.002
> 212.23.10.129 85.199.214.99 2 u 118 1024 1 19.929 202.213
> 0.002
> 178.79.155.116 85.199.214.99 2 u 120 1024 1 13.391 201.057
> 0.002
> 185.121.25.242 85.199.214.99 2 u 121 1024 1 14.084 200.964
> 0.002
> 81.21.65.169 195.195.221.100 2 u 122 1024 1 17.587 200.121
> 0.002
> 178.62.6.8 68.166.61.255 2 u 122 1024 1 13.864 200.580
> 0.002
>
>
> I'm beginning to wonder my testing using Meinberg polling every 10 seconds
> is causing the Pi an issue!
>
> remote refid st t when poll reach delay offset
> jitter
>
> ==============================================================================
> *127.127.28.0 .GPSD. 1 l 13 64 377 0.000 144.454
> 69.663
> o127.127.22.0 .PPS. 0 l 12 32 377 0.000 59.311
> 19.278
> uk.pool.ntp.org .POOL. 16 p - 1024 0 0.000 0.000
> 0.002
> 212.23.8.6 195.66.241.2 2 u 491 1024 1 13.316 200.644
> 0.002
> 212.23.10.129 85.199.214.99 2 u 489 1024 1 19.929 202.213
> 0.002
> 178.79.155.116 85.199.214.99 2 u 491 1024 1 13.391 201.057
> 0.002
> 185.121.25.242 85.199.214.99 2 u 492 1024 1 14.084 200.964
> 0.002
> 81.21.65.169 195.195.221.100 2 u 493 1024 1 17.587 200.121
> 0.002
> 178.62.6.8 68.166.61.255 2 u 493 1024 1 13.864 200.580
> 0.002
>
> Stopped monitoring, see if it stops...
>
> Thanks for your comments
> ==============================================
>
> Andrew,
>
> Three thoughts:
>
> - any chance the DCD pulse is the wrong polarity? Triggering on the
> trailing an not the leading edge? Might give errors typically around 100
> ms (the pulse width), but your errors seem to be more in the 250-300 ms
> range.
>
> - WNRO (week number roll over) issue?
>
> - unless you need stand-alone operation, try commenting out the type 28
> driver.
>
> I'd suggest the NTP Questions list, but it is /very/ fussy in what e-mail
> provider it accepts. Only one of my four works!
>
> https://lists.ntp.org/listinfo/questions
>
> Cheers,
> David
> --
> SatSignal Software - Quality software for you
> Web: https://www.satsignal.eu
> Email: david-taylor at blueyonder.co.uk
> Twitter: @gm8arv
>
>
> _______________________________________________
> time-nuts mailing list -- time-nuts at lists.febo.com
> To unsubscribe, go to
> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
> and follow the instructions there.
>
> _______________________________________________
> time-nuts mailing list -- time-nuts at lists.febo.com
> To unsubscribe, go to
> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
> and follow the instructions there.
>
More information about the Time-nuts_lists.febo.com
mailing list