[ntp:questions] Second attempt at GPS-18 based NTP server
David J Taylor
david-taylor at blueyonder.co.uk.invalid
Thu Feb 2 12:01:07 UTC 2012
> Hello All,
> I've (temporarily) given up on the idea of using Linux for the OS, and
> moved to FreeBSD, with the same GPS hardware, using some of the
> information on this web page:
> ntpq -p now says:
> remote refid st t when poll reach delay offset
> *dns1.rmplc.co.u 220.127.116.11 2 u 25 64 1 6.889 1.226
> 18.104.22.168 22.214.171.124 3 u 24 64 1 5.600 4.940
> GPS_NMEA(1) .PPS. 0 l 39 64 1 0.000 0.826
> So, I *think* that everything is okay, and it is using the PPS signal.
> There is one slight worry, which is what I see in /var/log/messages:
> Feb 2 09:50:16 tock ntpd: refclock_nmea: time_pps_kcbind failed:
> Operation not supported
> Please note, I have not done any recompiling of the kernel at this
> stage - just using the GENERIC kernel, because after reading the
> comments from Per Hederland in the System software customisation section
> of the above web page, it seemed unnecessary. Comments?
> Thanks for your help!
I know little about FreeBSD, so I don't know what the error message means.
I would wait a little while, and if the "reach" for the GPS_NMEA(1)
reaches 377, I reckon you're OK. On the Intel Atom system here, it shows
offset: 0.002 and jitter: 0.004 (these are in milliseconds).
I would have expected the poll for the GPS/PPS driver to be 16, and not
64. Here's an extract of what I have in the ntp.conf:
server 127.127.20.1 mode 0 minpoll 4 maxpoll 4 prefer
fudge 127.127.20.1 flag1 1 flag3 1 refid PPS
server 0.uk.pool.ntp.org iburst minpoll 10 maxpoll 10
server 1.uk.pool.ntp.org iburst minpoll 10 maxpoll 10
server 2.uk.pool.ntp.org iburst minpoll 10 maxpoll 10
Forcing the Internet servers to be 1024s polling always. I don't have any
note that I needed to recompile the kernel, so perhaps it was an install
If you find any errors on the Web page, or there is something you would
like explained better, or to add, please tell me. I'm glad you found it
helpful - well, some of it!
More information about the questions