Re: GPSD doesn't report signal dropout

[Tom Isaacson]

gpspipe files:
https://www.dropbox.com/s/34wt0usoe29uap4/json.log?dl=0
https://www.dropbox.com/s/m7zhce4wulv0o18/raw.log?dl=0

This is with the antenna connected for 10 seconds (approx),
disconnected for 10 then reconnected for 10.

Protocol document:
https://www.dropbox.com/s/ie3v7ijhdjc9xre/Quectel_EC2526EC21_GNSS_AT_Commands_Manual_V11.894777683.pdf?dl=0


On Wed, Oct 7, 2020 at 3:20 PM Gary E. Miller <gem@rellim.com> wrote:
>
> 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



-- 

Tom Isaacson