Problem migrating from legacy to ntpsec

[Hal Murray]

Jim Pennino said:

> After an upgrade to Ubuntu 24.04.1 I found legacy ntp had been replaced
> by = ntpsec-1.2.2 and the reference clock no longer works

> The relevant lines from ntp.conf are:
>   server 127.127.20.0 mode 16 minpoll 4 iburst
>   fudge 127.127.20.0 time1 -0.0007 flag1 1 flag2 0 flag3 1 refid PPS 

The flag1 1 mode doesn't get used much.  I setup a test system and 
couldn't get it to work.  Looks like you have found a bug.

The flag3 1 option doesn't work on kernels from most distros.  It 
conflicts with some power saving option.  If you really want that option, 
you will have to build your own kernel.  It does make a big difference.  
That's what causes this error message:
   REFCLOCK: refclock_params: kernel PLL (hardpps, RFC 1589) not 
implementedntpd

This is what I use for testing:

# NMEA: GPRMC, stats
server 127.127.20.0 path /dev/ttyS0 prefer mode 0x10001
fudge  127.127.20.0 flag1 0             # disable PPS
fudge  127.127.20.0 time2 0.167         # offset for NMEA signal

# PPS: needs ldattach 18 /dev/ttyS0
server 127.127.22.0 ppspath /dev/pps0   # PPS signal, needs prefer
fudge  127.127.22.0 flag2 0             # Rising edge

tos mindist 0.075                       # default is 0.001 (1 ms)

On systems with a kernel that supports internal PPS processing:
fudge  127.127.22.0 flag3 1             # use kernel PLL


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