Re: [Linuxptp-users] How to configure a grand master

[Keith S. <kei...@gm...>]

I apologize, but I'm completely new to all this timekeeping stuff, and I'm
very confused.

How do I feed the 1 PPS to the PHC? Do I use phc2sys? What API do I use to
read the 1 PPS time stamps from the PHC and set the PHC?

Instead of feeding the PPS to the PHC, reading the time stamps from the
PHC, and then setting the PHC to match the GPS time, wouldn't it be better
to have a separate program that reads the PPS and time from the GPS and
sets the PHC? Of course, then I wonder what the point of the PPS is if I
have the time from the GPS.

Is it really this difficult to synchronize a system to a GPS receiver, or
am I overthinking things?

On Wed, Aug 1, 2018 at 10:34 PM Richard Cochran <ric...@gm...>
wrote:

> On Wed, Aug 01, 2018 at 04:00:02PM -0500, Keith Squier wrote:
> > 1. How do I get the time from the GPS receiver to PTP?
>
> Ideally you feed the 1 PPS from the GPS into your PHC.  Then write a
> program that reads out the 1 PPS time stamps from the PHC and
> disciplines the PHC to match the GPS time.
>
> You can then optionally use phc2sys to synchronize the Linux system
> time to the PHC.
>
> Regarding TAI-UTC, the GPS does provide the information needed to
> figure that offset.
>
> HTH,
> Richard
>