Re: [chrony-users] Trouble with PPS

[Alvaro Gamez <alvaro.gamez@xxxxxxxxxx>]

2018-04-17 9:00 GMT+02:00 Miroslav Lichvar <mlichvar@xxxxxxxxxx>:

On Tue, Apr 17, 2018 at 08:28:43AM +0200, Alvaro Gamez wrote:
> #- GPS                           0   4   377    28    +11ms[  +11ms] +/-
> 9045us
> #* PPS                           0   4   377    27   +109us[ +105us] +/-
> 388us
>
> Why is GPS marked as not combined, though?

Because its distance (the +/- value) is significantly larger than the
PPS refclock's. Only PPS should be used for synchronization as it's a
much better time source.

You might want to add the noselect option to the GPS refclock
directive to not consider it for selection at all. Otherwise, it would
be good to at least increase its distance with the delay option to not
get two falsetickers if the offset between them changes. The example
in chrony.conf man page uses both.

But PPS by itself can't provide datetime, only second synchronization.

What would happen if I don't let chrony select GPS clock? Would it know what time is it?

PPS signal comes from the same device as GPS data, so their distance shouldn't ever vary, right?

BTW, all your messages appeared on my spam folder, I don't know why!
That's why it may look like I ignored your previous messages, sorry!

--

Álvaro Gámez Machado