[Xastir] Okay, so it only transmits when the GPS interface is started?

[Curt Mills]

On Wed, 5 Mar 2003, Curt Mills, WE7U wrote:

> Here's the relevant portion from main.c:UpdateTime():
>
>
>                 // Decrement the my_position_valid variable if we're
>                 // using GPS.  This will make sure that positions
>                 // are valid, as we'll only get four positions out
>                 // maximum per valid GPS position.  If the GPS
>                 // position goes stale, we'll stop sending posits.
>                 if (using_gps_position && my_position_valid) {
>                     my_position_valid--;
> //fprintf(stderr,"my_position_valid:%d\n",my_position_valid);
>
>                     if (!my_position_valid) { // We just went to zero!
>                         // Waiting for GPS data..
>                         statusline(langcode("BBARSTA041"),1);
> //fprintf(stderr,"my_position_valid just went to zero!\n");
>                     }
>                 }
>
>
> It looks like we stop transmitting positions if we think we have a
> GPS interface configured and enabled, and we stop getting positions
> from that interface.
>
> I'll do some more checking to make sure I understand the
> "using_gps_position" variable and how/when it gets set/reset.

It appears that we set "my_position_valid" to zero when start up any
GPS/networked-GPS port, otherwise its default is 1.  When we
correctly parse GPS data, we set it to three.  Each time we transmit
a posit if we're in GPS mode, we decrement it.  This keeps us from
transmitting stale GPS data if we lose the signal.  In that case, if
we're moving, dead-reckoning should take over on other people
screens and cover us until we get GPS lock again.

Starting up a GPS port increments "using_gps_position".  Shutting
down a GPS port decrements it.  If all GPS ports are shut down, it
should be at 0 and you should start posit'ing again.

I see one hole in the theory though.  If you start up a GPS port
without good data being decoded and then shut down the port again,
there's no code to set my_position_valid to 1.  In that case you
shouldn't posit again until you shutdown and restart.  I suppose
that'd be an easy one to fix in the code though.

Could that be what happened to you?

-- 
Curt Mills, WE7U                    hacker_NO_SPAM_ at tc.fluke.com
Senior Methods Engineer/SysAdmin
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