On 2017-10-31, valizade...@gmail.com <valizade...@gmail.com> wrote: > i have a ntp server based on Raspberry Pi3 with PPS (from u-blox6 ). i have > also added a hardware clock to this system. > > > SOME times there is a large offset(3-18 sec) on the SHM (ntp driver 28).
What program is delivering the time to the SHM? gpsd? > i did some experiments and figured out it is related to "leap seconds". No idea how it could be related to leap seconds. Leap seconds are only one second and that almost never happens. Is your gps broken? > when i COLD-RESET the ublox(via USB through u-center) this offset appears on > the ntp and both PPS and SHM become false-tickers. > > > i wait for over 12.5 minutes so that the UTC time become accurate (Almanac > data reception period) some times it works and SHM/PPS become truechimers and > some times even after 24 hrs they still are falsetickers with "3 seconds" > offset! It really sounds like a broken gps to me. > > here is what i think: > 1- system is tured on > 2- utc time is not accurate(leap seconds) but ntp dosent care and do iburst > 3- system time become updated > 4- 12.5 min is passed > 5- GPS time is changed (3-18 sec) > 6- ntp is not able to handle this > > > > i also used leap-second list file but there was no change > http://support.ntp.org/bin/view/Support/ConfiguringNTP#Section_6.14. > > > *****************system power on:*************** > Every 1.0s: ntpq -p PI3: Tue Oct 31 07:18:25 2017 > remote refid st t when poll reach delay offset jitter >============================================================================== > oPPS(0) .kPPS. 0 l 1 8 17 0.000 -5.553 2.806 > *SHM(0) .GPSD. 1 l 1 8 37 0.000 4.468 5.104 > LOCAL(1) .LOCL. 3 l 39 8 20 0.000 0.000 0.002 a) why do you have LOCAL as one of your clocks. That should basically never be used. It is useless except in very particular situations where it is a server which has to keep serving time even if its time is completely useless, because all clocks in an organisation have to on the same time, even if that is wrong. b) Do you have some other source of time? > > *****************after ~20 min:***************** > Every 1.0s: ntpq -p PI3: Tue Oct 31 07:39:28 2017 > remote refid st t when poll reach delay offset jitter >============================================================================== > oPPS(0) .kPPS. 0 l - 16 377 0.000 -4.023 0.355 > *SHM(0) .GPSD. 1 l - 8 377 0.000 1.894 1.650 > LOCAL(1) .LOCL. 3 l 1302 8 0 0.000 0.000 0.000 > > ***************** COLDSTART ***************** > Every 1.0s: ntpq -p PI3: Tue Oct 31 07:44:09 2017 > remote refid st t when poll reach delay offset jitter >============================================================================== > oPPS(0) .kPPS. 0 l 17 8 374 0.000 -2.423 0.661 > *SHM(0) .GPSD. 1 l 17 8 374 0.000 -0.057 0.652 > LOCAL(1) .LOCL. 3 l 1583 8 0 0.000 0.000 0.000 > > *****************after COLDSTART ***************** > Every 1.0s: ntpq -p PI3: Tue Oct 31 07:44:17 2017 > remote refid st t when poll reach delay offset jitter >============================================================================== > +PPS(0) .kPPS. 0 l 25 8 370 0.000 -2.423 0.661 > *SHM(0) .GPSD. 1 l 1 8 371 0.000 3044.83 3045.01 > LOCAL(1) .LOCL. 3 l 1591 8 0 0.000 0.000 0.000 > > *****************after COLDSTART ***************** > Every 1.0s: ntpq -p PI3: Tue Oct 31 > 07:44:37 2017 > remote refid st t when poll reach delay offset jitter >============================================================================== > xPPS(0) .kPPS. 0 l 45 8 340 0.000 -2.423 0.590 > xSHM(0) .GPSD. 1 l 5 8 347 0.000 3044.73 2573.41 > LOCAL(1) .LOCL. 3 l 3 8 1 0.000 0.000 0.002 > > > > > ntp.conf: > > tos maxdist 16 > tos mindist 0.400 > > > server 127.127.22.0 minpoll 3 maxpoll 4 > fudge 127.127.22.0 refid kPPS flag3 1 flag2 0 > > server 127.127.28.0 minpoll 3 maxpoll 4 iburst prefer > fudge 127.127.28.0 time1 +0.145 flag1 1 refid GPSD stratum 1 > > server 127.127.1.1 minpoll 3 maxpoll 4 #hwcloak > fudge 127.127.1.1 stratum 3 That is not the hardware clock. It is the system clock. It is completely useless. At present there is no evidence of anything. You do not have any independent source of time, so you have no idea what the time actually is. Put in some network time sources, so you at least have a small idea of UTC actually is. Eg pool.ntp.org > _______________________________________________ questions mailing list questions@lists.ntp.org http://lists.ntp.org/listinfo/questions