[OZAPRS] A Remote GPS.

Noel Rowe noel-r at clear.net.nz
Tue Nov 19 07:33:25 EST 2002


Darryl,

>Using the com-port loopback method it sounds like what you ware wanting
>is a small PIC processor to convert the MIC-E RS-232 string into a
>$GPRMC type GPS string? Is that correct.

Yes, that could work, as long as we can "get at" the data string as its
not
RS232 unless we make it so.
 See story below.

>Of course you may be able to take some virtual serial port software and
>modify it with some processing...

Thats possible also.  The virtual softwareI am using  is the
one provided by the MixW team, and it can be found at -
http://mixw.net/related.htm  in the section about TNC emulation.


Problem :  The TinyTrak sends a mic-e (compressed) beacon, and the other
(non APRS) program we need to run needs an RS232 or virtual $GPRMC NMEA
sentence.

So we need to extract the beacon after demodulating (if thats the right
word) the audio received by the radio on shore, and processed in the PC by
the AGW packet engine software using the sound card as the interface.
Then
in either external hardware or internal software we need to recreate the
$GPRMC NMEA sentence to as it was prior to the TinyTrak compressing it.
The
program we want to run expects the GPS to be on a serial port, and we need
to simulate that.

The following almost does it :-

http://www.kh-gps.de/micenmea.htm

But it needs the mic-e signal in to be as if it was output by a TNC2 in
KISS
mode.  We dont use a TNC, but the same signal must lurk within AGW-pe
somewhere, as other packet programs can run as if in KISS mode when using
AGW.

I have the virtual serial port software from the mixW site running fine
(needs WinXP) and the last mods made to UI-View (V1.84) allows you to
input
a GPS at a serial port for running say a laptop with UI-View, and output
via
another (real or virtual) port,  to say a nav program shareing the GPS
data.

Cheers, Noel, ZL3GR.


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