[ntp:questions] Using PPS
David Taylor
david-taylor at blueyonder.co.uk.invalid
Thu Dec 27 14:37:12 UTC 2012
On 27/12/2012 10:55, Joshua Small wrote:
> Hi,
>
> I built an NTP server with a GPS and PPS as per this guide (exact hardware):
>
> http://open.konspyre.org/blog/2012/10/18/raspberry-pi-time-server/
>
> I got things up and running with the same result as per said guide, before determining that my PPS wasn't wired up correctly.
> I fixed that, and now I'm sure it's wired up - it's now detected in dmesg, and ppstest indicates it's running.
>
> As far as any NTP diagnostic I can find goes however, nothing is any different (it feels like I have less drift, but I didn't keep graphs before), which leads me to the question of "how do I know it's working?".
>
> As per the guide, I run this in ntp.conf:
>
> server 127.127.20.0 mode 17 minpoll 3 iburst true prefer
> fudge 127.127.20.0 flag1 1 time2 0.496
>
> I can definitely see, in ntpq -p, the GPS_NMEA driver being used.
>
> I can see a related thread here:
>
> http://ml.enneenne.com/pipermail/linuxpps/2009-February/002888.html
>
> Specifically, my googling generally pointed me at looking for PPSSIGNAL in the status, however, it seems that a lack of it (as is my case) is "normal" in many circumstances.
>
> Any advice appreciated.
>
> -Josh.
Josh,
My own notes on the Raspberry Pi are here:
http://www.satsignal.eu/ntp/Raspberry-Pi-NTP.html#pps
I hope there is some useful diagnostic information there. You should a
"o" against the PPS source in the "ntpq -p" output, and a "kern" entry
in the "ntpq -c rv" output.
Here are the results from my Raspberry Pi:
C:\Users\David>ntpq -c rv 192.168.0.14
associd=0 status=011d leap_none, sync_pps, 1 event, kern,
version="ntpd 4.2.7p329 at 1.2483 Sun Dec 2 09:10:46 UTC 2012 (1)",
processor="armv6l", system="Linux/3.2.27-pps-g965b922-dirty", leap=00,
stratum=1, precision=-19, rootdelay=0.000, rootdisp=1.135, refid=PPS,
reftime=d486da8e.004dd4ef Thu, Dec 27 2012 14:32:46.001,
clock=d486da97.0dff9b5b Thu, Dec 27 2012 14:32:55.054, peer=2679, tc=4,
mintc=3, offset=0.001799, frequency=-41.199, sys_jitter=0.002386,
clk_jitter=0.000, clk_wander=0.000
C:\Users\David>ntpq -p 192.168.0.14
remote refid st t when poll reach delay offset
jitter
==============================================================================
oPPS(0) .PPS. 0 l 8 16 377 0.000 0.002
0.002
*pixie .PPS. 1 u 14 32 377 0.511 -0.012
0.031
+FEENIX .PPS. 1 u 17 32 377 0.605 0.028
0.028
+Stamsund .PPS. 1 u 6 32 377 0.601 -0.039
0.135
uk.pool.ntp.org .POOL. 16 p - 1024 0 0.000 0.000
0.002
-time.mhd.uk.as4 213.229.82.130 3 u 396 1024 377 24.654 13.474
5.664
-dawn.rt.uk.eu.o 193.79.237.14 2 u 1066 1024 377 19.163 2.598
3.815
-cadmium.cloudfa 195.66.241.2 2 u 103 1024 377 26.394 2.699
3.609
-time.dan.me.uk 82.148.230.254 2 u 787 1024 377 17.598 0.409
3.568
--
Cheers,
David
Web: http://www.satsignal.eu
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