Re: UBLOX and NTPD

[Gary E. Miller]

Yo Joseph!

On Tue, 19 Mar 2024 16:31:36 -0500
Joseph Beissel <joebeis64@gmail.com> wrote:

>    - Using a UBLOX M8

Which submodel?  M8N?  M9T?

>    - Using GPSD 3.17 due to system built on Yocto Warrior (I know,
> sucks for me...)

Yup.

> I can run gpsd  on and directly connect to our gps device using the
> following command:
> 
> gpsd -b -nN8 /dev/ttyPS1 2>&1 | tee /tmp/gpsd_direct.log

Running with -b is discouraged.

> The command "ipcs -m" shows the shared memory segments.  The segment
> at 0x4e545030 has two processes attached to it (nattch=2).  I assume
> one is gpsd and the other is ntdp.  I can run ntpshmmon and see
> samples being written to the shared memory segment:

Got some output of that?

> sample NTP0 aaaa.aaaa bbbb.bbbb cccc.ccc (repeats with different
> values

Pretend data is not useful.

> Running the "date" command on the box shows the correct date and time.

What does ntpmon say?

> Now I change things up a bit.  I stop gpsd and start our custom
> application that attaches to the gps device (/dev/ttyPS1) and
> forwards all UBX and NEMA messages to another device (/dev/ttyGPS0).
> I know there's better ways to do this but other software relies on
> some of the things that our cucstom aplication does and we can't
> change that for now (down the road most likely).  So having our
> application forward all messages is the best we can do for now.

Not rare.

> I then startup gpsd as follows:
> 
> gpsd -b -nN8 /dev/ttyGPS0 2>&1 | tee /tmp/gpsd_indirect.log

What is /dev/ttyGPS0?  A real device?  A loopback device?  A pipe?

> The command "ipcs -m" shows the shared memory segments.  The segment
> at 0x4e545030 has two attached to it (nattch=2).  I assume gpsd and
> ntpd are the same as above.

You are saving the logs.  Reading the logs will allow you to now
make assumptions.

> When I run ntpshmmon I do not see any
> samples being written to the shared memory segment.

The answer will be in the log.

> Since I used "N8" I compared the 2 logs created.  One thing I noticed
> is that the variable ntpshm_link_activate is set differently for the
> direct connection (/dev/ttyPS1) then it is for the indirect connection
> (/dev/ttyGPS0):
> 
>    - direct(/dev/ttyPS1): ntpshm_link_activate=1
>    - indirect(/dev/ttyGPS0): ntpshm_link_activate=0

Not much I can do woth log fragments.  Please sned the FULL logs.

> I am not sure if this is causing my problem. 

No link, means no SHM output from gpsd.  That would be your problem.

> And I am not sure why
> it is not set to "1".  Would this keep the shared memory segment from
> being written to?

Yup.

> If so, what keeps it from getting set to "1"?  Or
> is there something else that I am missing.  I used the
> not-supported-terrible-tool gpsmon when running in the indirect
> configuration and things look good,

We never care what gpsmon says.  We care what the logs say.

> I also compared the 2 logs to see what UBX and NMEA messages are
> being sent and they appear to be the same for the direct and indirect
> casses.

I woud like to do the same, but...

> In the direct case I captured the UBX raw configuration
> messages that gpsd sends to the device and made sure that our custom
> application was doing the same.  In addition I compared the NMEA
> messages and they appear to be identical as well.

You are now totally lost.

> Also, one more question about sending messages to this group.  When I
> get a reply to  a message that I posted, how do I reply to it?

Without knowing yur email client, we can't know.  I use claws-mail.  I just
type 'R'.

Ansking questions, without the data to answer them, is not useful.


> Do I
> simply use "reply all" or is there another way?

"Reply Sender".  Assuming your email client is not brain dead and knows
that "gpsd-users" is the sender.

> If the reply comes
> from gem, will a "reply-all" be sent to gem directly?

NOTHING comes from me, only from the list.  Please do not do Reply-all.

> I thought I
> read that it is taboo since I am not a paying customer.  Want to make
> sure I am doing the right thing by the user group.

"Reply-sender" is the way.

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

pgpfVc55iQcCM.pgp
Description: OpenPGP digital signature