Re: GPS and NTPD.

[Gary E. Miller]

Yo Joseph!

On Sun, 17 Mar 2024 17:39:12 -0500
Joseph Beissel <joebeis64@gmail.com> wrote:

> Which segment does NTPD use?

Which ever ones you tell it to.  Common ones are SHM(0) to SHM(7).
When running as root often SHM(0) and SHM(1).  When not root SHM(4) and
SHM(5).

> Does it use both segments to
> determine/set the time?

What ever you tell it to.

> I was not aware that there are two ways that
> the time can be set.

Two?  Dozens!

> What I am thinking about doing is leveraging our existing
> implementation that configures the device and reads the messages and
> add to it the ability to forward all messages to another tty (i.e.
> /dev/gps0).   Then start gpsd up using this tty.

Or, you could have gpsd manage the device, and send NMEA to your code.

> I prototyped
> something along these lines to test it out but I didn't see anything
> when I ran ntpshmmon and the time was not getting set.  I did see
> that gpsd was reading messages correctly using the gpspipe tool.

To debug, run gpsd with the "-ND5" options.

> I know this is probably a convoluted way to do this but time and
> money do not allow us to do more.

Time is money.

> In our next release I plan to go
> full gpsd.

Cool.

RGDS
GARY
---------------------------------------------------------------------------
Gary E. Miller Rellim 109 NW Wilmington Ave., Suite E, Bend, OR 97703
        gem@rellim.com  Tel:+1 541 382 8588

            Veritas liberabit vos. -- Quid est veritas?
    "If you can't measure it, you can't improve it." - Lord Kelvin

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