bugGPSD - Bugs: bug #60288, Warmup: Missing TPV with no GPS fix


bug #60288: Warmup: Missing TPV with no GPS fix

Submitter:  Armin Schlegel <siredmar>
Submitted:  Thu 25 Mar 2021 11:28:28 AM UTC
Category:  None Severity:  3 - Normal
Item Group:  None Status:  None
Privacy:  Public Assigned to:  None
Open/Closed:  Open
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Fri 26 Mar 2021 08:49:48 AM UTC, comment #1: 

I digged around a little bit more. It seems like NMEA 2.3 does not have the mode indicator (FFA) field. That confirms what i can read here: https://gpsd.gitlab.io/gpsd/NMEA.html#_sentence_mixes_and_nmea_variations

So my initial thought about the mode indicator can be nullified as the `status` (valid values A,D,V) gets evaluated. (https://gitlab.com/gpsd/gpsd/-/blob/master/drivers/driver_nmea0183.c#L506) The status field seems to be the backward compatible case. So this seems correct to me.

So for now, i cannot see what is going wrong here.

Armin Schlegel <siredmar>
Thu 25 Mar 2021 11:28:28 AM UTC, original submission:  


I am fully aware that i am warming up some old issues.
I am referencing to bug #52055 and the discussion on gpsd-dev mailing list: https://lists.gnu.org/archive/html/gpsd-users/2016-11/msg00013.html

It seems like both the bug and the mailing lists topic did not fix the issue.
I am using gpsd version `gpsd: 3.19 (revision 3.19)`

After writing a gpsd golang library i was trying to test it with the real gpsd (instead of gpsfake). Currently my modem does not have an antenna connected, so the raw output seems like this:

>(20) $GNGLL,,,,,,V,N*7A
>(66) $GNGST,,0.0000,9324070,9324070,0.0000,3750632,3750632,3750632*7F
>(21) $GNZDA,,,,,00,00*56
>(19) $GNGBS,,,,,,,,*5F
>(25) $GNRMC,,V,,,,,,,,,,N*4D
>(21) $GNVTG,,,,,,,,,N*2E
>(33) $GNGGA,,,,,,0,00,99.99,,,,,,*56
>(45) $GNGSA,A,1,,,,,,,,,,,,,99.99,99.99,99.99*2E
>(45) $GNGSA,A,1,,,,,,,,,,,,,99.99,99.99,99.99*2E
>(18) $GPGSV,1,1,00*79
>(18) $GLGSV,1,1,00*65

Notice that the `mode indicator` (last value before checksum) in RMC is `N` what means `No fix`.
Notice that the `fix quality` (first `0` character in string) is `0` what means `Invalid`.

What i expect is that TPV objects are sent with at least `mode=1` or `mode=0` (0=unknown,1=no fix).
Instead no TPV message are sent at all.

This seems like a bug to me. What do you think?


Armin Schlegel <siredmar>


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