[Xastir] Help with TH-D72 run in PACKET and get at GPS?

[Alex Carver]

--- On Mon, 1/17/11, Kurt Savegnago wrote:

> 
> (Sorry about the hijack but it clarifies my reply and
> questions below)
> 
> As I understand it, The D72 can be used as a stand alone
> tracker with the TNC selected in the APRS mode or one can
> have the TNC in PACKET mode and control the TNC from a
> program like UI-View, Xastir or APRSIS32 with WINE.
> 
> When in PACKET mode, I don't think there is a way to
> extract the GPS information into the computer.  I said,
> "I don't think." :-) 
> I could be wrong. ;-)  If I am, show me the
> way............

Yes, this was also available with the original D7 and D70 but only ONE NMEA sentence will come through.  Unless the D72 got a much bigger and faster processor there aren't enough resources to echo every NMEA sentence that the GPS spits out over the serial link.

> If there is a way to route the GPS info from the D72 while
> it is in PACKET mode to the laptop via a USB sertial
> comverter, I'd like to know as it would negate the need for
> a USB GPS receiver.  I used a USB receiver I plugged
> into my Linux/Xastir laptop to give it position information
> and the D7A(g) for receive/transmit purposes while the A(g)
> was in PACKET mode.

If the TNC is behaving the way the D7 and D700 TNCs did then there's a GPSHEAD command but that gives you only one NMEA sentence instead of all of them so it makes the GPS rather useless for navigation because not all information is available in all NMEA sentences (e.g. altitude, lat/long, and time aren't all available simultaneously in one sentence).


> Is the GPS information available at the 2.5mm jack while
> the D72 is in PACKET mode?  If so, then a 2.5mm plugged
> cable to a DB9, going through 
> a USB serial converter should give the GPS position info to
> the laptop.

You could always just plug in a cable and see what happens. :)  I suspect the port behaves just as the GPS port did on the D7 and D700 that it's input only (for the most part) and will send out only waypoint data if there's an external GPS sitting there.  Otherwise it's not doing anything with the internal GPS.  The manual gives no indication one way or another so some experimentation is in order.  Won't hurt the radio to plug it into your computer and see what comes out.

> If this is possible, would eliminate the need for a USB GPS
> receiver to be plugged into the laptop but.......... The
> battery consumption would go up in the D72 with it's GPS
> on.  In the field, I have a reservoir of electrons in
> the form of a high capacity 12V battery with an AC inverter
> for the laptop.  The USB GPS pulls it's juice from the
> laptop and the 
> "reservoir". :-)

Give it a shot, just plug in the radio into an available serial port (keep a null modem adapter on hand in case there's a pin swap) and see what shows up on the port.


(off-topic:  if you're out in the field a lot I would highly recommend investing in a DC-DC converter for your laptop instead of the AC inverter. It's more efficient (longer run time on your battery) and would be a lot smaller, you could even hide it away in the car so it's always available)

>