[ntp:questions] Have Pi, have GPS = low powered NTP server?
g8kbv at uko2.co.uk
Thu Jun 7 10:30:46 UTC 2012
In article <MPG.2a3016d85d1683449896d0 at news.btopenworld.com>,
spam at goes.nowhere.com says...
> From the title, you might (maybe) guess this is about the Raspberry Pi,
> and NTP.
> pi at raspberrypi:~$ ntpq -p
> remote refid st t when poll reach delay offset jitter
> *ntp.websters-co 126.96.36.199 2 u 11 128 377 37.918 -7.068 20.879
> +ns1.luns.net.uk 188.8.131.52 2 u 65 128 377 34.099 -5.716 197.916
> +ns0.luns.net.uk 184.108.40.206 2 u 64 128 377 33.914 -6.204 181.881
> -time.xilo.net 220.127.116.11 3 u 101 128 377 25.476 -29.662 4.126
> (A little bit of reformatting to fit here has been done)
I've sort of temporaraly deployed it on the home LAN (literally hanging
by it's LAN cable!) sync'ing to the existing BSD based time server.
The stat's are now more encouraging, showing delay, offset and jitter
arround 0.500 units, when left overnight. See below.
Interestingly, it's decided to cease accessing the few external servers
I told it about (all uk.pool based) just sticking to the local Stratum 1
box. Or they have gone offline now...
pi at raspberrypi:~$ ntpq -p
remote refid st t when poll reach delay offset jitter
*192.168.42.24 .GPS. 1 u 362 1024 377 0.563 0.669 0.284
time.xilo.net 18.104.22.168 3 - 5h 1024 0 21.571 13.885 0.000
dns0.rmplc.co 22.214.171.124 2 - 5h 1024 0 2019.75 -1000.8 0.000
I grabbed that via a remote SSH link, so I know the DSL at home is
working, else I wouldnt have been able to get this data. Both the
external servers were reach=377 when I last looked last night.
If those delay/offset and jitter figures are in milli seconds (?) could
that be down to the USB hosted LAN port on the Pi? The same figures for
the BSD box at 192.168.42.24 are 0.000 0.004 and 0.002 respectively, I
just remoted into that and checked.
That is using a GPS with PPS via a real COM port, and has a 10/100LAN
port. The LAN between the two, is via a 10/100 full duplex switch, a
generic Netgear domestic plastic 8 port type, nothing special, except
I've somehow managed to fill all 8 ports!
The next check, will be to use it as a time source itself for one of the
beacon monitors. I'll be using the Faros machine for that, as it can
show me how well the known time references are behaving relative to each
other, and the received beacon times..
I'm still on a near vertical learning slope with this RasPi thing, and
Linux in particular, but I do see that other activity (remote access by
SSH/VNC etc) does not seem to disturb it that much.
Guess I need to look into using the onboard serial port for a GPS at
some point, if that's releasable from whatever it might be tied to at
present. But that would still leave the USB<>LAN behaviour in the loop
for the downstream users.
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