PIC Based APRS Beacon

[germanium]

This is for all you ham radio guys.  I put this together to make a simple APRS (position reporting via packet radio) beacon for flying on high altitude balloons but of course you could use it to track the location of a vehicle as well.  It's based on a PIC18F2525 and I build it using MPLAB-X and the Microchip XC8 compiler in PRO mode.  The PIC generates the AFSK audio signaling directly with a resistor network, sort of a primitive 4 bit DAC which you can hook up to an FM transmitter. 

The PCB layout is done with Eagle.  I have a Trimble Copernicus GPS module on there but any GPS that outputs NMEA strings will work without modification.  The code only makes use of the $GPGGA and $GPRMC sentences.  Packets are output in the binary MIC-E format.  The code also logs the GPS NMEA strings to the onboard SD card.  I used the popular CHaN FatFS library so the card can be formatted FAT and read with a standard PC and text editor.  Have fun... :-)

[charudatt]

http://www.kh-gps.de/minitnc.htm
This is the simplest one