Re: PPS stopped once => stopped forever?

[Gary E. Miller]

Yo Ulrich!

On Mon, 28 Oct 2024 06:28:53 +0000
"Wielant, Ulrich" <U.Wielant@leonardogermany.com> wrote:

> >> + gpsd -V
> >> gpsd: 3.25 (revision 3.25)  
> >
> >Still on old gpsd...  Newer gpsd handles serial drops better.  
> 
> Yea, I will put that on my TODO list to check the latest git code.

You could have updated in less time than it took to write your email.

> >The python parts of gpsd are missing!  
> 
> I don't use python so does it matter to me?

Only matters if you want many of the gpsd features to work.

> >> # To allow gpsd remote access, start gpsd with the -G option and #
> >> uncomment the next two lines:
> >> # ListenStream=[::]:2947
> >> # ListenStream=0.0.0.0:2947  
> >
> >You are running under systemd(umb) which is configure to not allow
> >-G.  
> 
> Ok, I may remove -G because I use local connections only.

That works.

> Anyhow where would I have to uncomment the lines?

The file you are probably looking for is: /lib/systemd/system/gpsd.socke

That file is NOT part of gpsd.  It is part of systemd(umb), and
I never use systemd(umber).

> The gpsd man page
> does not mention the ListenStream config.

gpsd does not document that file because that file is not part of
gpsd.

> >> crw------- 1 root root    249,  0 Oct  8 12:51 /dev/pps0  
> >
> >Note that pps0 is root only!  
> 
> I can change that to 666. Does that mean that gpsd can use PPS again
> when the GPS is back again?

Nope.  It was a long ago design decision that when PPS  is lost, it
can only be regained by restarting.  In normal operation that should
rarely happen.


> >I need the entire log, from startup, to see what I need to see.
> >Without that not much I can see in the gpsd_stop_pps.log  

> The entire logs are *big* because the problem does not occur often.

Yes.

> Is there any good way to strip down the logfile so that all
> interesting things remain?

Nope.

> >Anything in dmesg after the failure?  
> 
> No, just:
> [1279323.350188] pps pps0: removed
> [1279473.387246] pps pps0: new PPS source serial0 [1279473.387273]
> pps pps0: source "/dev/ttyS0" added

Odd.  Must be another systemd bug.

> >Note that SHM(0) and SHM(1) are root only, but your gpsd has already
> >dropped root.  So gpsd can no longer open pps, SHM(0) or SHM(1).  
> 
> Ok, understood. Is there any way to change that?

No.  But you can use SHM(2) and SHM(3).  That is not a good idea.

> I am using chrony. Does this problem disappear by using sockets
> instead of SHM?

Nope.  It is a design decision.

> >You clearly have a bug in the path from the receiver to /dev/ttyS0.
> >Can yuo tell us something about that path?  Receivers come in
> >various voltage versions and a mistmatch causes issues like this.  
> 
> The receiver accepts 8-32Vdc and is connected with 24Vdc.
> >

Sorry that I was not clear.  I  did not mean the power supply voltage.
I need the voltage on the TX, RX, and PPS lines.  Both the spec
on the GNSS receiver side, and on the motherboard side.  Mismatch is
the most common way for serial ports to fail.

TX/RX/PPS lines can be: +/- 12V, 0 to 12V, 0 to 5V, 0 to 3.3V, 0 to
1.8V, Or even other combinations.  But 32V and 24V is not one of them.
Mixing and matching is not obvious and leads to failures similar to what
you are seeing.

> So that's ok.

Facts not in evidence.

> But I am more and more convinced that the GPS firmware is buggy
> and the GPS sometimes resets.

That would be extremely rare.  What is your receiver model and frmware
version?

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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