[LinuxPPS] Synchronizing a ZDA message with NTP using linuxPPS

[Udo van den Heuvel]

On 2010-03-20 21:03, Divi.Oillo at ifremer.fr wrote:
> Here is my new ntp.conf:
> #134.246.11.121
> server ntpserver minpoll 4 maxpoll 16
> 
> #Undisciplined Local Clock
> server 127.127.1.0 minpoll 4 maxpoll 16
> 
> #Generic NMEA GPS Receiver
> server 127.127.20.0 mode 8 minpoll 4 maxpoll 16
> fudge 127.127.20.0 flag1 1 flag2 0 flag3 1
> 
> #PPS Clock Discipline
> server 127.127.22.0 minpoll 4 maxpoll 16
> fudge 127.127.22.0 flag2 0 flag3 1
> 
> techsas:~> ntpq -pn
>       remote           refid      st t when poll reach   delay   offset  jitter
> ==============================================================================
> x134.246.11.121  .1PPS.           1 u    9   16  377    0.180   15.760   1.266
> *127.127.1.0     .LOCL.           5 l    8   16  377    0.000    0.000   0.001
> x127.127.20.0    .GPS.            0 l    7   16  377    0.000  -61.472   0.244
>   127.127.22.0    .PPS.            0 l    -   16    0    0.000    0.000   0.000

Hmm.
There is a timestamp coming in from the GPS but it's offset appears too
big. (see the NMEA clock)
Also the external clock is not really used. Why is the LOCL clock
stratum 5?! Please `fudge   127.127.1.0 stratum 15`.
The external clock should provide the timestamps for now. That should
work first.

The PPS appears not to be working, at least not for the PPS refclock.
Please disable the NMEA clock and test again.
See pps coming in via e.g. `cat /sys/devices/virtual/pps/pps*/assert`
See the ntpd receive PPS as well.
Reachability should not be 0.

Udo