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[gpsd-dev] Missing TPV when there is no fix

From: Piotr Figiel
Subject: [gpsd-dev] Missing TPV when there is no fix
Date: Mon, 18 Sep 2017 14:50:08 +0200

 on recent gpsd [1] I stumbled on an issue similar to one reported
already in the past [2] that TPV with mode = 1 (MODE_NO_FIX) is not
being sent by the gpsd when the fix is lost. Instead no TPV at all was
received by the clients by the time there was no fix. This affects use
case when it's expected to detect fix loss on libgps client.
 On my receiver (Telit's SL869, but I also remember this appearing in
the past on HE910) the scenario is easily reproducible with cgps:
 - wait for receiver to get fix,
 - run cgps,
 - disconnect antenna,
-> cgps still shows 3D fix despite the RMC sentences (as observed with
gpspipe) show that fix was lost.
I isolated the issue so that it's reproducible with attached log file
used with gpsfake (-c 1) - gpsfake simulates sequence: no fix -> fix
-> no fix -> etc...
I introduced correction which now I'm testing and it resolves the
issue. It's attached, can you please review and merge if applicable?

Best regards,
Piotr Figiel.

[1] confirmed on master, 3db781b747e03df8faa71a8d4281f9294e05084b but
also in past versions

Attachment: RMC2.tmp.log
Description: Text Data

Attachment: 0001-nmea-0183-report-MODE_NO_FIX-when-there-is-no-fix.patch
Description: Text Data

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