Background
We'd like to synchronize the PPS source with an NTP source. We can see the PPS signal on /dev/pps1 is working:
# ppstest /dev/pps1
trying PPS source "/dev/pps1"
found PPS source "/dev/pps1"
ok, found 1 source(s), now start fetching data...
source 0 - assert 1641833656.999979198, sequence: 4162 - clear 0.000000000, sequence: 0
source 0 - assert 1641833657.999977707, sequence: 4163 - clear 0.000000000, sequence: 0
source 0 - assert 1641833658.999977549, sequence: 4164 - clear 0.000000000, sequence: 0
The NTP tools have been uninstalled:
ntp.service not-found inactive dead ntp.service
ntpsec.service not-found inactive dead ntpsec.service
openntpd.service not-found inactive dead openntpd.service
We've disabled the GPS daemon.
Problem The output from running 'chronyc sources' shows that the 1PPS signal is "not combined":
MS Name/IP address Stratum Poll Reach LastRx Last sample
===============================================================================
#- PPS 0 4 377 13 -92ns[ -260ns] +/- 1000ns
^* 192.168.67.200 1 4 377 11 +26us[ +26us] +/- 1086us
^? 192.168.67.201 0 4 0 - +0ns[ +0ns] +/- 0ns
When we had ntpq installed, running 'ntpq -pn' yielded:
remote refid st t when poll reach delay offset jitter
==============================================================================
*192.168.66.196 129.6.15.28 2 u 6 16 377 0.225 +0.778 0.009
127.127.1.0 .LOCL. 2 l 65h 16 0 0.000 +0.000 0.000
o127.127.22.1 .PPS. 0 l 11 16 377 0.000 +0.001 0.002
The
'o' indicates the PPS signal is locked and the '*' indicates that the
NTP server is being used as one of the time sources alongside PPS.
Configuration The refclock is configured as follows:
reflock PPS /dev/pps1 refid PPS
We're using chronyd version 3.4 on a 32-bit ARM and have tried using both the pre-built package and a custom build.
We tried setting 'combinelimit 0' to no avail.
Questions When using the chronyc command, we would like to know:
- What
status symbols should we see when 1PPS and NTP are synchronized and
locked (e.g., '*' for PPS and '*' for the NTP address)?
- Does the '-' beside PPS mean that the PPS signal is locked?
- What does "not combined" mean?
- Can we disambiguate between having no PPS signal, having a PPS signal, and having a locked PPS signal? If so, how?
- If
"not combined" is not the correct final state, what do we need to
change in the configuration file to ensure that 1PPS will be locked and
synchronized?
Thank you!