Hi all, On 01/23/2017 05:43 PM, Lloyd Dizon wrote: > Hi. > See below. > > On Mon, Jan 23, 2017 at 4:54 PM, Jan Ceuleers <jan.ceule...@computer.org> > wrote: > >> On 23/01/17 12:25, Lloyd Dizon wrote: >>> I've installed a GPS module on a Raspberry Pi and I'm getting 1000ms >>> offsets between the GPS readings and network NTPs. >> >> Could you show us the relevant extracts from your ntp.conf file related >> to the GPS source? That is: at least the server line and any fudge lines? >> > > enable mode7 > > # Local > #server 127.127.1.0 > #fudge 127.127.1.0 stratum 10 > > # GPS with PPS enabled > server 127.127.20.0 mode 17 minpoll 6 maxpoll 6 iburst true prefer > fudge 127.127.20.0 time1 1 flag1 1 refid GPS
Why do you add one full second time correction to the time PPS stamp? I admit that having the output of ntpq in millisecs and the config vaues in seconds is confusing, but 'time1 1' adds a full second to the PPS time stamp. This shouldn't be needed -- PPS delay correction is in the sub-millisecond range if it's used at all. If you have problems with a huge delay between PPS and your first NMEA sentence of a new burst, use fudge time2 (!!) to compensate for that. This can just lead to assigning a wrong second to the PPS value, see http://support.ntp.org/bin/view/Support/ConfiguringNMEARefclocks https://support.ntp.org/bin/view/Support/ConfiguringGarminRefclocks http://doc.ntp.org/current-stable/drivers/driver20.html I'm using a GPS18x-LVC with the following settings: server 127.127.20.0 mode 33 noselect minpoll 4 maxpoll 8 fudge 127.127.20.0 flag1 1 time2 0.51 refid GPSc Note the time2 offset of 510msec that I need to get the NMEA data stream aligned with the PPS signal. If I don't do this, I end up with the wrong second assigned to the PPS signal, too. > > # Internet time servers for sanity > server 0.ch.pool.ntp.org iburst prefer > server 1.ch.pool.ntp.org iburst > server 2.ch.pool.ntp.org iburst > server 3.ch.pool.ntp.org iburst > > # By default, exchange time with everybody, but don't allow configuration. > restrict default kod limited nomodify notrap nopeer noquery > restrict -6 default kod limited nomodify notrap nopeer noquery > > # Local users may interrogate the ntp server more closely. > restrict 127.0.0.1 > restrict -6 ::1 > > # Drift file etc. > driftfile /var/lib/ntp/ntp.drift > _______________________________________________ > questions mailing list > questions@lists.ntp.org > http://lists.ntp.org/listinfo/questions > _______________________________________________ questions mailing list questions@lists.ntp.org http://lists.ntp.org/listinfo/questions
