[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
[gpsd-users] Large ntp.conf time1 offset needed with GPSD shared memory
From: |
Jon Brase |
Subject: |
[gpsd-users] Large ntp.conf time1 offset needed with GPSD shared memory driver |
Date: |
Tue, 09 Aug 2016 03:02:16 -0500 |
User-agent: |
Opera Mail/12.16 (Linux) |
Just a quick question: Is it typical for the data that GPSD hands to NTP
through the shared memory driver to arrive with a ~500 ms offset from
top-of-second as shown by PPS (where NTP is pulling the PPS data directly)
or by external timeservers? The hardware is a Raspberry Pi running
Raspbian Jessie with an Adafruit GPS breakout, with the following server
configuration in /etc/ntp.conf:
------------------------------------------------------------------------------
#coarse time from GPSD
server 127.127.28.0 minpoll 4 maxpoll 4 prefer
fudge 127.127.28.0 time1 0.47 refid GPS
#PPS ref-clock for top-of-second
server 127.127.22.0 minpoll 4 maxpoll 4
fudge 172.127.22.0 refid PPS
# pool.ntp.org maps to about 1000 low-stratum NTP servers. Your server
will
# pick a different set every time it starts up. Please consider joining
the
# pool: <http://www.pool.ntp.org/join.html>
server 0.debian.pool.ntp.org iburst
server 1.debian.pool.ntp.org iburst
server 2.debian.pool.ntp.org iburst
server 3.debian.pool.ntp.org iburst
------------------------------------------------------------------------------
I found that I needed a time1 offset in the .45 to .5 range (currently
.47, as shown above), to get the coarse GPS time to line up with the PPS /
external timeserver time. Is this typical? I'm just wanting to make sure
that it doesn't indicate some gross misconfiguration, as half a second
seems like a rather large fudge. If everybody here thinks everything is
fine, though, I think I will be ready to take leave of this list, as this
is the last outstanding GPSD-specific issue I have with my GPS timeserver
project.
On that note, what's the most appropriate forum for discussing general
issues with setting up a GPS timeserver (for example, some of the output
I'm getting from ntpq doesn't match what the references I used for setup
lead me to expect, and I suspect misconfiguration or other problems with
ntpd)?
--
Jon Brase
- [gpsd-users] Large ntp.conf time1 offset needed with GPSD shared memory driver,
Jon Brase <=
- Re: [gpsd-users] Large ntp.conf time1 offset needed with GPSD shared memory driver, Jon Brase, 2016/08/09
- Re: [gpsd-users] Large ntp.conf time1 offset needed with GPSD shared memory driver, Gary E. Miller, 2016/08/09
- Re: [gpsd-users] Large ntp.conf time1 offset needed with GPSD shared memory driver, Jon Brase, 2016/08/10
- Re: [gpsd-users] Large ntp.conf time1 offset needed with GPSD shared memory driver, Gary E. Miller, 2016/08/10
- Re: [gpsd-users] Large ntp.conf time1 offset needed with GPSD shared memory driver, Jon Brase, 2016/08/16
- Re: [gpsd-users] Large ntp.conf time1 offset needed with GPSD shared memory driver, Gary E. Miller, 2016/08/16
- Re: [gpsd-users] Large ntp.conf time1 offset needed with GPSD shared memory driver, Jon Brase, 2016/08/17
- Re: [gpsd-users] Large ntp.conf time1 offset needed with GPSD shared memory driver, Jon Brase, 2016/08/17