Re: [chrony-users] GPS + PPS

[Bill Unruh <unruh@xxxxxxxxxxxxxx>]

On Sun, 26 Oct 2014, Dominik Auras wrote:

> Hi,
>
> thanks.
>
> Chrony selects the PPS source now, but I observe a large offset of the system time.
> The offset to the PPS clock is nearly zero, as expected. But the system time is
> offset by >2000s to the NMEA and NTP time (I won't have internet access once
> deployed).

What does NTP time mean? 
Are you sure you are not reading your system time in your own timezone, and
forgetting that the ntp time is in UTC?

You also give us no information

It would also be usefull to see a selection of the refclock log file, to see
what is coming in on the various refclocks.


> To the previously mentioned configuration, I've added simply noselect to the GPS
> refclock.
>
> Any other idea?
>
> BR, Dominik
>
> 2014-10-26 2:31 GMT+02:00 Tomalak Geret'kal <tom@xxxxxxxxx>:
>       On 26/10/2014 00:28, 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
>
> 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
>
>
> I've had this problem in the past, but could never figure out what was going
> on. Listers suggested that it was a chrony bug but I was never able to gather
> enough information to pin it down.
>
> Marking your SHM source as "noselect" prevents chrony from getting stuck when
> deciding which of the two refclock sources is a better match, but doesn't
> prevent the "lock GPS" declaration from linking the two SHM sources together.
>
> So:
>
> server ptbtime1.ptb.de iburst noselect maxpoll 6 minpoll 6
> refclock SHM 0 refid GPS offset 0.546 poll 6 delay 0.9999 noselect
> refclock SHM 1 delay 0.2 refid PPS lock GPS
> minsamples 64
> makestep 1000 -1
>
> Perhaps give that a go.
>
> Tom