Re: UBLOX and NTPD

[Gary E. Miller]

Yo Joseph!

On Wed, 20 Mar 2024 12:39:02 -0500
Joseph Beissel <joebeis64@gmail.com> wrote:

> Running gpsd in two configurations:
> 
>    1. running gpsd directly attached to the gps device (debug output
> in attached file gps_direct.log)

Did you read this?  You have hardware problems:

gpsd:IO: <= GPS: $GNTXT,01,01,01,More than 100 frame errors, UART RX was 
disabled*70

Nothing we can do about that.  A lot of these weird serial drivers are
broken.  That means gpsd init will fail.  And it did.  Which is why your
device  ends up in NMEA 0183 mode.

But it does do good SHM(0):

gpsd:PROG: NTP: ntpshm_put(/dev/ttyPS1,-20)  1710934881.000000000 @  
1708975027.178745117

>    2. running custom application that attaches directly to the gps
> device and forwards all messages to another device (debug output in
> attached file gps_indirect.log)

We can't really support that usage.   Unless you setup the receiver
in a way that gpsd can use it, your results will be marginal.  Too many
variables out of our control.

> In the direct configuration gpsd is connected directly to device
> "/dev/TTPS1" (Ublox).

And what driver creates a /dev/TTPS1 ??  Clearly problems there.

> For the indirect configuration, we use openpty() to create a
> pseudo-terminal.

gpsd knows nothing of pseudo-terminals.

> We only use the FD returned for the master (ignore
> slave).

Lost me.  I'll have to read up on those.

>  We then create a symbolic link to the pseudo terminal called
> "/dev/ttyGPS0".

Why bother with a link?

> Output of "ipcr -m" shows the same for both configurations running.

Which is jumping WAY past the first failure.  No point looking there.
Always look at the first failure, not later failures.  For example: you
don't care the convertible roof failed on a car after it rolled over,
after it blew a tire.  The first failure, the tire blowing, is what you
look at.

The indirect is in a mashup of NMEA 0183 mode and u-blox mode.  So this
is commparing apples to oranges.

The message decode is setting NTPTIME and TIME flags, but not sending to
SHM(0).  later versions of gpsd have loging to show why, but in your case
I could only guess that your sentence mix is confuing the end of cycle
detector.  Beyond that, nothing I can do.

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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