Re: [chrony-users] GPS + PPS

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On Sun, 26 Oct 2014, Dominik Auras wrote:


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 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               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            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

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