Re: GPSD Not Using /dev/pps0 But ppstest Shows /dev/pps0 is OK

[Gary E. Miller]

Yo Joshua!

On Wed, 2 Dec 2020 11:24:16 -0500
Joshua Quesenberry <engnfrc@gmail.com> wrote:

> I'm running GPSD on an RPi 4. I have GPSD pulling in the GPS data over
> serial without any issues. Now I'm trying to pull in to the PPS
> signal that is on GPIO 6.

A common thing to do.  I assume you read the HOWTO on that?

Where did you get your gpsd from?  Was it build with MAGIC_HAT?

> I've added to /boot/config.txt the line:
> `dtoverlay=pps-gpio,gpiopin=6` and appended to /etc/modules line
> `pps-gpio`

You do not need to modify /etc/modules.  The dteoverlay= already brings
in the pps-gpio module.

> and now after a reboot I see pps_gpio and pps_core loaded.

And what does dmesg say about it?

> Using command `sudo ppstest /dev/pps0` I see this output, which
> confirms to me that /dev/pps0 is in fact my PPS signal coming into
> the RPi.
> 
> trying PPS source "/dev/pps0"
> found PPS source "/dev/pps0"
> ok, found 1 source(s), now start fetching data...
> source 0 - assert 1606924323.767119450, sequence: 205 - clear
> 0.000000000, sequence: 0

Good.  At least considering the poor pps-gpio module...

> I then modified my GPSD startup script

Uh, what gpsd startup script?  For what distro?

> such that now when the app is
> running I see this process: `/usr/sbin/gpsd -r tcp://127.0.0.1:5760
> /dev/pps0`

That look wrong.  No "-n", extra "-r", and what is tcp://127.0.0.1:5760?

Running as root?

> Now from what I can tell reading around in the documentation gpsmon
> should have something showing in the PPS field and ntpshmmon should
> be outputting something, however both the PPS field is empty and
> ntpshmmon isn't outputting anything at all.

Not surprising, given your odd configuration.

Does gpsmon sow a 3D fix?  And a good location?

> Can someone give me guidance on the next steps?
> 
> Version Information:
> gpsd: 3.17 (revision 3.17)

3.17 is really old.  UPdate to 3.21 or git head.

> # Socket export enabled.
> # Shared memory export enabled.
> # DBUS export enabled
> # Time service features enabled.
> # PPS enabled.

Any reason you did not go with the gpsd build defaults?

> Note that this gpsd binary was provided through the apt package.

Then not from us, gpsd does not distribute any packages.  What distro?
So we can't patch it.

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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