| Re: [chrony-users] GPS + PPS |
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On Sun, 26 Oct 2014, Dominik Auras wrote:
Hello!
I am trying to setup chrony for my new GPS. Unfortunately, chrony won't select any
source if I enable both the NMEA and PPS source. I bet that my configuration is
wrong ... but it is unclear to me how to configure the PPS.
Could you maybe explain me what I do wrong, or point me to something that explains
it? Thank you in advance!
Part of my chrony.conf
Why don't yuo try paring things down a lot. Get rid of the poll, delay
directives. Also you have those delay directives. Why?
I presue you are using gpsd to read the nmea and gps.
Why the minsamples directive?
chrony adapts the samples to the wander of the offset. If the offset it
wandering, the relation is no longer linear and using more samples makes
everything much worse, not better, and stops chrony from reacting to things
like temperature changes.
server ptbtime1.ptb.de iburst noselect maxpoll 6 minpoll 6
refclock SHM 0 refid GPS offset 0.546 poll 6 delay 0.9999
refclock SHM 1 delay 0.2 refid PPS lock GPS
minsamples 64
makestep 1000 -1
Output of chronyc sources:
210 Number of sources = 3
MS Name/IP address Stratum Poll Reach LastRx Last sample
===============================================================================
#x GPS 0 6 377 82 -21.0s[ -21.0s] +/- 503ms
#x PPS 0 4 377 22 +16ms[ +16ms] +/- 100ms
^x ptbtime1.ptb.de 1 6 377 46 -21.0s[ -21.0s] +/- 30ms
Output of chronyc sourcestats
210 Number of sources = 3
Name/IP Address NP NR Span Frequency Freq Skew Offset Std Dev
==============================================================================
GPS 64 21 67m -0.646 4.511 -21.0s 11ms
PPS 64 23 1009 3.062 0.006 +16ms 3620ns
ptbtime1.ptb.de 64 33 69m 2.952 0.191 -21.0s 498us
The PPS is the rpi_gpio_ntp program running in the background.
chrony won't have internet access once it is deployed ...
BR, Dominik