[ntp:questions] Have Pi, have GPS = low powered NTP server?

Kennedy, Paul P.Kennedy at fugro.com.au
Wed Aug 29 09:07:37 UTC 2012

Hi Dave,
good feedback.
I have had the pi running for several days now without a hitch.  Due to
my dynamic IP (pending a static ip), you can find the pi and associated
ntp server at:


I made a small realtime time-series plot and a page displaying ntpq info
so I can more easily review performance.

I fully intend to use serial GPS+PPS when it arrives (slow boat from
china), but will continue to build the web site for monitoring the
service in the meantime. I am currently building the web page to add
additional ref clocks.

I do se occasional spikes in the offset.  you can see them in the timer
series plots which are based on loopstats files.  I would hope they
disappear when I have pps.  I am not sure if this is pi/ethernet or the
refclock (which is not close-by).  My final use-case is on our internal
LAN's at work where we have a GPS unit always on hand, but this is a
homework project right now, so the going is a bit slow.

I have not seen any lockups yet, and will try to keep it running as long
as possible without a reboot.  If you have seen it, I am sure it will
pop up for me as well.  If we get them, the pi is a showstopper for me.


-----Original Message-----
From: questions-bounces+p.kennedy=fugro.com.au at lists.ntp.org
[mailto:questions-bounces+p.kennedy=fugro.com.au at lists.ntp.org] On
Behalf Of DaveB
Sent: Wednesday, 29 August 2012 4:32 PM
To: questions at lists.ntp.org
Subject: Re: [ntp:questions] Have Pi, have GPS = low powered NTP server?

In article <

b0590fa0-d352-4ce0-8504-7708460900c9 at googlegroups.com>,
pktrigg at gmail.com says...
> Hi,
> I have my pi running on the web right now at
> I made a small web site to expose various parameters in realtime. 
> Still waiting for my gps unit, but I am pretty happy with millisecond 
> from live internet sources.  PPS is next.
> The website needs a little more polish, but the basics are there.   Unreachable, 08:19 UTC Wednesday 29th August.

I've seen on another site, that people using the chipset based serial
port with GPS and other devices, and have *Much* better results than
when using a USB hosted serial port.

There are still issues with the Pi's network port, as that aparrently is
a USB driven device on board, resulting in more latency than might be
expected otherwise, and some extra variability too.

I also found that the Pi would lock up and need a power cycle, if left
running the default NTPD service for anything more than two or three
days.  It was predictable and repeatable, but I've not tried updating 
the OS (or NTP) and doing that again.   That was using the original 
Debian distro for the thing.

At this exact time, it's back in it's box while I make room for it by
doing other things, much more important according to domestic 
management.   I have other plans for it.


Dave B.

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