[time-nuts] looking for low-power system for gps ntp timekeeping NANOSG20

[David J Taylor]

Hi,

I decided to buy a Nanos G20. Not too expensive, real serial port,
debian linux pre-installed.
I don't want to sound harsh as the people from Nanos probably did their
best to produce a good product, but for timekeeping it is totally crap
and also useless.
Well, unless I did something wrong.
I recompiled the kernel to enable PPS support, installed gpsd and ntpd,
configured at all and let it run for a while.

allan deviation: 
http://keetweej.vanheusden.com/~folkert/nanosg20/allandev.png

offset: http://keetweej.vanheusden.com/~folkert/nanosg20.png

     remote           refid      st t when poll reach   delay   offset 
jitter
==============================================================================
x127.127.28.0    .NMEA.           0 l    3   16  377    0.000  -994.05 
7.857
x127.127.28.1    .PPS.            0 l    7   16  377    0.000  -250.13 
572.812
+192.168.64.18   .PPS.            1 u   66  128  377    0.553   -0.055 
0.033
*192.168.64.2    .PPS.            1 u   99  128  377    0.237   -0.062 
0.039
+192.168.64.168  .PPS.            1 u   44  128  377    0.646   -0.013 
0.321


Folkert van Heusden
======================================

Folkert,

Thanks for your graphs, but what are the Y-axis units!

Inn your billboard above, the PPS looks to be on the wrong edge - perhaps 
the pulse is 250 ms wide and you are syncing to the trailing edge and not 
the leading.  Can you check that out?  I recall that it's the positive going 
transition on the DCD connection which needs to be on the exact second.   I 
think you are using the Garmin GPS 18x LVC.  There was a firmware update 
which ensured that the serial adta arrived /before/ the /next/ second edge 
rather than after it.  Ensure your firmware is 3.70 or later.  See:

  http://www.satsignal.eu/ntp/Garmin-GSP18x-LVC-firmware-issue.htm

I see that 3.80 is now out, but I think I am still on 3.70.

Hope that helps....

Cheers,
David
-- 
SatSignal Software - Quality software written to your requirements
Web: http://www.satsignal.eu
Email: david-taylor at blueyonder.co.uk