[aprssig] New OpenTracker firmware release

[Scott Miller]

I've released a significant update to the OpenTracker firmware, and it's now
available for download from http://n1vg.net/opentracker/downloads.php.  The
configuration program has been updated as well, so you'll need to get the
new version to be able to use the new firmware.

Briefly, new features and fixes:

GPS HDOP and number-of-satellites data can be displayed in comment text
Timeslotting support
TXD range is expanded for slower radios
Experimental support for PTT input (mic-encoder style)
Setting TX interval to 0 disables timed transmissions
Battery voltage display is now more accurate
You can now see what firmware version you've got loaded
Negative altitudes work right now
Text comments can be sent as separate status packets every n transmissions

I think the GPS fix quality data is the only thing really unique to the
OpenTracker.  The periodic status packet feature is useful for sending
static data like email addresses - I think the TT3 has the same option.

The age of the current GPS fix is also tracked internally, but nothing is
done with it yet.  I'm considering expanding the number of configuration
profiles to four and adding GPS fix age as a switch parameter.  Basically,
that'd let you set up a state machine with four states to handle failure
conditions.  This would be particularly useful for balloons - I'm planning
to add a 'continuous tone between packets' option that'd let you do
direction finding on a downed tracker.  It'll cost another 256 bytes of
flash for the extra profiles, though, and things are starting to get tight.

Some sample data from the latest firmware, status packet every 3
transmissions, with battery voltage, temperature, HDOP, and number of
satellites in the comment field:

fm N1VG-6 to APOT02 ctl UI pid=F0(Text) len 15
 >scott at n1vg.net
fm N1VG-6 to APOT02 ctl UI pid=F0(Text) len 53
 !3325.54N/12128.37W>020/011 08.4V 19C HDOP12.3 SATS08
fm N1VG-6 to APOT02 ctl UI pid=F0(Text) len 53
 !3325.59N/12128.35W>020/011 08.4V 19C HDOP12.3 SATS08
fm N1VG-6 to APOT02 ctl UI pid=F0(Text) len 53
 !3325.65N/12128.33W>020/011 08.4V 19C HDOP02.3 SATS08
fm N1VG-6 to APOT02 ctl UI pid=F0(Text) len 15
 >scott at n1vg.net
fm N1VG-6 to APOT02 ctl UI pid=F0(Text) len 53
 !3325.71N/12128.31W>020/011 08.4V 19C HDOP02.3 SATS08

Looks like that battery's about dead.  Anyway, OpenTracker users can just
download the latest config program and firmware, and use the 'erase' option
on the first screen to load the new firmware.  The source archive will be
updated in a bit, if anyone cares.

Scott, N1VG
http://n1vg.net/opentracker