[Xastir] Xastir and the TH-D72 on OSX Mac

[Tom Russo]

On Tue, Jul 05, 2011 at 11:29:23AM -0700, we recorded a bogon-computron collision of the <curt.we7u at gmail.com> flavor, containing:
> On Tue, 5 Jul 2011, Lynn W. Deffenbaugh (Mr) wrote:
> 
> > When receiving GPS data within the APRS input stream from a radio, do you 
> > know if you expect it to be wrapped in an APRS-looking packet header (like 
> > MYCALL>GPS:$GPRMC) or just a raw NMEA sentence ($GPRMC,....*xx)?  The 
> > difference is the setting of LTMHEAD on the radio's TNC when enabling LTMON.
> 
> If I remember correctly it's looking for the NMEA headers, no APRS headers for GPS data.

Yes, that's right.  The raw NMEA string is what Xastir's expecting, not
a NMEA-in-APRS packet.

> The "Serial TNC w/GPS on AUX Port" interface was designed for the KPC-3+ TNC and Paccom PicoPacket TNC's which can send a GPS string down when you send it a Control-E character.  As I recall they send only the captured GPS string, so it starts with "$GP".

It also works with the D700 so long as you have a "GPSTEXT" command in the
startup file to tell the TNC to send periodic NMEA sentences of that type.  
I don't know that the radio is caring about the control-E in
this case --- it may just stream the NMEA data regardless, and Xastir is
just OK with that because the NMEA and APRS data are both expected on that
port, unlike a plain Serial TNC interface.

Apropos of nothing in particular, the D700 can only send one type of $GP 
sentence at a time, the one specified in GPSTEXT.  The internal APRS firmware 
gets both GPRMC and GPGGA sentences by repeatedly sending GPSTEXT commands to 
the TNC to switch the setting back and forth (watch the PMON sometime), but 
Xastir can't do that (we have no mechanism to send continuous commands to the 
TNC like that), so you have to pick one and have it apply to the whole session.
The default startup file selects $GPRMC.

My understanding is that the D72 cannot stream the NMEA sentences from the
internal GPS in any mode that also allows Xastir to use the TNC.  You need to 
use an external GPS to get the data to the serial port.  Really bad decision 
on their part, IMHO.

-- 
Tom Russo    KM5VY   SAR502   DM64ux          http://www.swcp.com/~russo/
Tijeras, NM  QRPL#1592 K2#398  SOC#236        http://kevan.org/brain.cgi?DDTNM
 "One man alone can be pretty dumb sometimes, but for real bona fide
 stupidity, there ain't nothin' can beat teamwork." - Edward Abbey