Re: NTP via tcp NMEA feed

[Gary E. Miller]

Yo Nick!

On Sun, 16 Oct 2022 12:10:30 +0100
Nick Taylor <nicktaylor@dataskill.uk> wrote:

> > Any idea what $GPHWBIAS is?

Got an answer for this?

> Maybe this was a red herring - I used different GPS device (Huawei
> ME936 Modem with GPS) due to my setup here and I think it's flawed.
> We are lucky that gpsd is clever enough to fix things up.
> 
> New test using the normal SIM68 feed shows the following:
> 
> nmea-raw.log is read direct from /dev/ttyS5 with socat
> 
> gpsd-serial.log is output from std working gpsd on local machine
> (ntpshm feed fine)

Thanks.  The side-by-side let me track it down to ntpshm_link_activate()
gpsd/timehint.c

Here is the code:

    /* don't talk to NTP when we're:
     *   reading from a file
     *   reading from a pipe
     *   reading from a remote gpsd
     *   running inside the test harness (PTY)
     *   over TCP or UDP
     */
    if (SOURCE_BLOCKDEV == session->sourcetype ||
        SOURCE_GPSD == session->sourcetype ||
        SOURCE_PIPE == session->sourcetype ||
        SOURCE_PTY == session->sourcetype ||
        SOURCE_TCP == session->sourcetype ||
        SOURCE_UDP == session->sourcetype) {
        return;
    }

I'll need to think  about it, but I think if I remove the SOURCE_GPSD
line, that may do the trick.  Any gpsd feed should be sorta real-time,
and if the NTP is setup correctly, bad time should be ignored.

You can try removing that line to see if it works for you.


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

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