[time-nuts] Raspberry Pi NTP server

Fri Jul 3 17:33:54 UTC 2020

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
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