Re: GPSD doesn't report signal dropout

[Gary E. Miller]

Yo Tom!

On Wed, 7 Oct 2020 15:08:47 +1300
Tom Isaacson <tom.isaacson@teknique.com> wrote:

> > I see no direct indication of antenna disconnect.  I don't think
> > NMEA understands the concpet.  AFAIK that requires a binary
> > protocol.  
> 
> I'm just disconnecting the antenna to simulate losing signal which you
> see in the messages.

I just use aluminum foil.  Some antenna connectors are not meant for
many cycles.

> I wrote a small test app using minmea
> (https://github.com/kosma/minmea) and it works fine so I'm not worried
> the data from the source is wrong.

Looking at nmea-disconnect.txt again, maybe not wrong, but unique.

Here is the event:

$GPGGA,004049.00,3644.762734,S,17444.080437,E,1,06,1.3,70.9,M,37.0,M,,*4A
$GPVTG,,T,341.7,M,0.0,N,0.0,K,A*0C
$GPRMC,004049.00,A,3644.762734,S,17444.080437,E,0.0,,071020,18.3,E,A,V*47
[...]
$GPVTG,,T,,M,,N,,K,N*2C
$GPGSA,A,1,,,,,,,,,,,,,,,,*32
$GPGGA,,,,,,0,,,,,,,,*66
$GPRMC,,V,,,,,,,,,,N*53

The order changed, which confuses the cycle detector, and it just
stopped giving time, which also confises the cycle detector.

gpsd has a ton of NMEA samples, but this is a new one.  You should send
a bug report to quectel.  After you get me some doc on the part.

There may be a workaround, but I need to gpspip logs to see.

> Client app is ours, but I wrote a small test app using the gpsd C++
> example and it shows the same problem:
> https://gpsd.gitlab.io/gpsd/client-howto.html#_c_examples_2

gpsd provides a lot of clients so that when debugging we know the
client app is correct.  See if cgps, or another standard client works.
But in this case it looks like "unique" NMEA.

> I'll try recording the data simultaneously with D5.

What I need is the gpspipe's.  I doubt we will need to -D5 if the
gpspipe NMEA looks the same as your sample.

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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