Re: [gpsd-users] Communication loss with GR-701W

[Gary E. Miller]

Yo Benoît!

On Mon, 20 May 2019 18:35:35 +0200
Benoît Thébaudeau <address@hidden> wrote:

> > 3.18 had a bug, which is why 3.18.1 cam out shortly therafter.  
> 
> I've upgraded to 3.18.1, but it does not help.

No, you just have not realized what it fixed yet.  :-)

> > When you hotplug the GPS gets reset to stored configuration.  You
> > should check how you have your GPS configured.  It is easy to 
> > program the u-blox to ouput no data on startup, that can cause
> > issues.  
> 
> Actually, there is data at the very beginning. See the log below.

I guess I'll get there in a bit.

> > The exact error would be nice.  Better yet the full log.  
> 
> Here is the full log:
> call gpsd:PROG: switching to match packet type 1:
> $GPGSV,2,2,08,20,40,119,37,21,52,059,37,26,58,164,39,27,53,290,20*7C\x0d\x0a

So you have NMEA.

> gpsd:IO: <= GPS:
> $GPGSV,2,2,08,20,40,119,37,21,52,059,37,26,58,164,39,27,53,290,20*7C
> gpsd:WARN: GPGSV field 3 value of 8 != actual count 4

Started mid-cycle.  Things will sync up.


> gpsd:INFO: Sats used (4): gpsd:IO: <= GPS:

And they did.

> gpsd:PROG: selecting u-blox driver...

Changed to -u-blox.

> gpsd:IO: UBX checksum 0x1b85 over length 108, expecting 0x3030

Bad checksums are not good.  Is this serial, RS-232 or USB?

> gpsd:IO: <= GPS: $GPTXT,01,01,00,trk tick 2 96000 dt 23881*3A
> gpsd:WARN: TXT: Error: trk tick 2 96000 dt 23881
> gpsd:IO: <= GPS: $GPTXT,01,01,00,trk tick 3 144000 dt 8694*36
> gpsd:WARN: TXT: Error: trk tick 3 144000 dt 8694
> gpsd:IO: <= GPS: $GPTXT,01,01,00,trk tick 5 240000 dt 5595*38
> gpsd:WARN: TXT: Error: trk tick 5 240000 dt 5595
> gpsd:IO: UBX: len 10

More error messages from the GPS.  Also not good.  The GPS is telling
us it is sick.

> As you can see, after the trk tick error, the only thing still
> working is the PPS.

Yeah, not good.  Of course that error is undocumented by u-blox.

> > Have you tried ubxtool to reset the configuration?  
> 
> Is it safe?

Yes.  The default config is in ROM, by design it is the safest thing
to do.

> I mean, I do not know the configuration the GR-701W ships
> with,

Yup, but likely it is the factory defaults.


> nor if gpsd may change this configuration on its own,

It certainly did, as shown by your logs.

> so I do
> not want to risk getting a malfunction because of this.

Too late, you already have a malfunction.

> > Sending different types of reset is easy with ubxtool.  
> 
> Sending a MON-HW2 poll (echo -ne '\xb5\x62\x0a\x0b\x00\x00\x15\x49'
> > /dev/ttyUSB0) results in: 00000000  b5 62 0a 0b 1c 00 fa 61  0f 5f
> > 70 00 00 00 ff ff  |.b.....a._p.....|
> 00000010  ff ff ff ff ff ff ff ff  ff ff 00 00 00 00 00 00
> |................| 00000020  00 00 5e
> 0f                                       |..^.|

That way is to hard, I'm not even going to try to hand decode that.

And no point, UBX-MON-HW2 has nothing to do with the current issue.

> So the module replies properly, which means that the baudrate is
> correct on both sides.

We already knew that.

> But it does not talk more after having sent
> this command.

Which one again sounds like a serial port issue.

> I still have to dump the whole internal state of the module to see if
> it reports anything abnormal.

Don't bother.  Just try to configure it properly, without saving or
resetting:

    # ubxtool -d NMEA
    # ubxtool -e BINARY


> Sending a CFG-RST/hotstart/HWreset (echo -ne
> '\xb5\x62\x06\x04\x04\x00\x00\x00\x00\x00\x0e\x64' > /dev/ttyUSB0)
> makes the module recover,

Wow, you like doing things the hard way.  How about:

    # ubxtool -p COLD

> but the issue can then still happen after
> replugging the module a few times.

Yes, because that reverts to the saved config.

> I cannot succeed in duplicating the issue when stracing gpsd, which
> may indicate that it is timing-related.

Which points again to potential serial problems.  Also potential
buffer overruns sending to the GPS at low speeds.

> > Also, since this happens on hotplug, how is your udevd setup?  
> 
> I'm just using the SysV gpsd.hotplug and 25-gpsd.rules installed by
> gpsd 3.18.1.

Good.  And since it does seem to detect the GPS, b4 failing, that is
not an issue.

RGDS
GARY
---------------------------------------------------------------------------
Gary E. Miller Rellim 109 NW Wilmington Ave., Suite E, Bend, OR 97703
        address@hidden  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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