| Re: [chrony-users] ntpd refclock drivers with chrony |
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It seems to be superfluity of ways to connect. I suspect users are going to
want some guidance as to which would be better to use. Criteria are probably
ease of setting up and use
accuracy of clock discipline.
computer resources needed.
Also, one might want to separate the nmea use from the pps use. They are
really independent, with nmea having pretty shitty timing (10s of ms rather
than microseconds) which might be OK for some, but for accuracy is useful only
for getting the conting of the seconds for the pps.
I have not tested the various pps timing methods. I am using pps-ldisc myself
even though I know that the serial port is slower at responding to an
interrupt than is the paralled port (unfortunately almost nothing has a
parallel port anymore). I have not tested gpio vs serial port. and my parallel
port tests are 20 years old by now.
William G. Unruh __| Canadian Institute for|____ Tel: +1(604)822-3273
Physics&Astronomy _|___ Advanced Research _|____ Fax: +1(604)822-5324
UBC, Vancouver,BC _|_ Program in Cosmology |____ unruh@xxxxxxxxxxxxxx
Canada V6T 1Z1 ____|____ and Gravity ______|_ www.theory.physics.ubc.ca/
On Tue, 28 Nov 2017, Miroslav Lichvar wrote:
There is a new wrapper for refclock drivers implemented in ntpd, which
should allow chronyd to use any refclock supported by ntpd. It's
primarily intended for users with refclocks which are not supported by
gpsd, but if anyone would like to try it with a GPS, it should work
too.
https://github.com/mlichvar/ntp-refclock
Comments, bug reports and pull requests are welcome. It should work
with the latest ntp release (ntp-4.2.8p10). A man page will be added
later.
The command line syntax is similar to the server and fudge directives
of ntpd. Here is an example using the NMEA driver at 115200 bps with
PPS enabled:
# ntp-refclock -s /var/run/chrony-GPS.sock -d -c log \
127.127.20.0 mode 80 time2 +0.5 flag1 1
With the SHM, ATOM and GPSD drivers in ntpd, it seems we now have 13
options how a GPS NMEA+PPS device can be used with chronyd. :)
Currently, I'd not recommend using the ATOM driver as it produces
samples even when the system clock is not synchronized. I don't have
much experience with the GPSD driver.
1) gpsd SOCK
2) gpsd SHM 0 + /dev/pps0
3) gpsd SHM 0 + ntp-refclock 127.127.22.0 (ATOM)
4) gpsd SHM 1
5) ntp-refclock 127.127.20.0 (NMEA) + /dev/pps0
6) ntp-refclock 127.127.20.0 (NMEA) + ntp-refclock 127.127.22.0 (ATOM)
7) ntp-refclock 127.127.20.0 flag1 1 (NMEA with PPS)
8) gpsd + ntp-refclock 127.127.28.0 (SHM) + /dev/pps0
9) gpsd + ntp-refclock 127.127.28.0 (SHM) + ntp-refclock 127.127.22.0 (ATOM)
10) gpsd + ntp-refclock 127.127.28.1 (SHM)
11) gpsd + ntp-refclock 127.127.46.0 (GPSD) + /dev/pps0
12) gpsd + ntp-refclock 127.127.46.0 (GPSD) + ntp-refclock 127.127.22.0 (ATOM)
13) gpsd + ntp-refclock 127.127.46.0 mode 1 (GPSD with PPS)
--
Miroslav Lichvar
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