Date: Sat, 31 Jul 2004 14:46:27 -0600 (MDT) From: "M. Warner Losh" <imp@bsdimp.com> To: oberman@es.net Cc: freebsd-stable@freebsd.org Subject: Re: Looking for ntp/PPS setup guide Message-ID: <20040731.144627.06076085.imp@bsdimp.com> In-Reply-To: <20040730000205.E834A5D09@ptavv.es.net> References: <200407292338.JAA18401@lightning.itga.com.au> <20040730000205.E834A5D09@ptavv.es.net>
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In message: <20040730000205.E834A5D09@ptavv.es.net> "Kevin Oberman" <oberman@es.net> writes: : > From: Gregory Bond <gnb@itga.com.au> : > Date: Fri, 30 Jul 2004 09:38:32 +1000 : > Sender: owner-freebsd-stable@freebsd.org : > : > : > We've got a GPS receiver to make an NTP server, and it has PPS output. : > Is there a guide to how to set up PPS on recent (4.10-ish) FreeBSD : > boxes? Or I can put it on a 5.x box if that is better. I've had a : > look in all the obvious places but the only references I can find are : > to old (load a line discipline or patch a kernel) solutions. : : I'd suggest the documentation at www.ntp.org, but it has a few errors : and lacks a bit of FreeBSD specific bits. : : First off, you will need to rebuild ntpd with the appropriate reference : clocks, pps and whatever type of GPS you have. The software is in : /usr/src/contrib/ntp/ntpd. You can look at the list of clock drivers and : pick the one you need. If you look at the driver source, you will see : that REFCLOCK and a driver specific variable need to be defined. : : Go to /usr/src/usr.sbin/ntp/ntpd and rebuild ntpd with the clock driver: : make clean : make -DREFCLOCK -DCLOCK_yourclock : make install : : You need to rebuild you kernel with "options PPS_SYNC". You can run PPS : without this and the man page even says it's more accurate that way, but : my experience is that it is much more accurate with the kernel option. : I use CDMA clocks and they my time is stable within 10 microseconds. I've found that w/o PPS_SYNC, we get worse results than when we have it enabled.Of course, most of my work with this is with a pps that is from a HP5071A atomic clock :-) : I did find that nptd 4.2 seemed to converge better than 4.1, so I built : the ntp port instead of the standard one. I then just installed the ntpd : from the port over the one in /usr/sbin. 4.2 is now the standard NTP in : version 5 and I suspect it will be MFCed to STABLE soon. : : Read the manual pages for pps and your GPS clock driver for how to set : up ntp.conf for that clock. You will need to set up kernel PPS there. This can be the hardest part. The documentation is a little less than stellar. :-( Warner
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