Yo Frank! On Thu, 5 May 2016 19:41:07 -0400 Frank Nicholas <fr...@nicholasfamilycentral.com> wrote:
> I haven’t used the NTP configuration below for years. I came up with > it from some recipe(s) I found online (some commented in the file). > The "time2 0.350" was the generally accepted best number for the > original Raspberry Pi A/B. I personally have no idea how to tune > NTP. I just used what I thought was the best information I could > find at the time. Easy with the 28 refclock. Not sure on the 20. DO you even see the coarse time with ntpq -p? > My current NTP server is part of pfSense (FW/Router/NTP/etc., based > on FreeBSD-10.3-RELEASE) Their web interface is limited in some of > the NTP/PPS/GPS settings you can easily get to. If you make changes > outside the web interface, you risk them being overwritten by the web > interface. I really need to get a good config nailed down & not > touch it. Once you have it how you like it, you only touch it for IP changes. > > On May 5, 2016, at 7:12 PM, Gary E. Miller <g...@rellim.com> wrote: > > > > I use the 28 refclock, you the 20. > > Regarding 28 ref clock, that is SHM? Why that rather than NMEA (20)? gpsd handles a lot more GPS types than #20. So let gpsd handle the GPS. gpsd passes the time it determines to ntpd using the SHM (shmctl) interface. The long term goal is to kill off #20 as no need to maintain 2 NMEA parsers. > > I use a time1 of 0.480 for my Ultimate GPS HAT. Just about in the > > middle of my 30 to 70 milliSec jitter. > > I don’t remember what the difference is between time1 & time2. time1 adjusts the PPS derived time, time2 adjusts the NMEA derived time. With #28, the NMEA time is on SHM1, and PPS time on SHM2. So each has its own reflock line, and fudge. Keeps from mashing things together and losing visibility. > What’s a good way to “tune” my NTP config? Compare it to another ntpd server and see which has the least jitter/wander. > What’s a good way to monitor my NTP performance? I stare at the results of: root@pi2:~# watch ntpq -p Watch how you local refclock(s) compare to some others. > Correct, 16 = 9600 & 1 = specified the NMEA sentence to get time > from, I think... I’ll look at upping it on my current > configuration. I had to limit the statements that came out, so they > didn’t run over the second (some periodic (every 5 or 10 seconds) > NMEA statements made it take > 1 second for a cycle). Thus the suggestions to go up from 9600. RGDS GARY --------------------------------------------------------------------------- Gary E. Miller Rellim 109 NW Wilmington Ave., Suite E, Bend, OR 97703 g...@rellim.com Tel:+1 541 382 8588
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