APRS Tracker

13 March 2017

Here is a very simple Arduino based APRS Tracker created with an Arduino Nano, an HC-05 Bluetooth Module, 8 resistors, 2 capacitors and a general purpose NPN transistor. Used inconjunction with a Smartphone running APRSdroid, it makes for a compact tracking package. The Arduino Tracker is based on an earlier Mobilinkd Tracker design you can find at http://www.mobilinkd.com/2014/09/11/arduino-kiss-tnc/. I added the HC-05 Bluetooth Module so a Smartphone can control the tracker without a cable attached to the phone. The only cable is between the tracker and the radio.

Here's the schematic:
https://sites.google.com/a/wt4y.com/radio/aprs-tracker/APRS-Tracker%20Schematic.png

R1-100k, R2-10k,R3-1k, R4-2.2K, R5 and R6-10K, R7-1k, R8-2.2K
C1-100nf, C2-10nf
Q1-NPN Transistor such as 2N2222, 2N3904 etc.

and a photo:

https://sites.google.com/a/wt4y.com/radio/aprs-tracker/APRS-Tracker.jpg

As a power supply, I'm using a battery pack composed of 6 ea. AA NImH batteries, but a single 9v battery will also work.

To flash the firmware into the Nano, you will need first need to download the compiled HEX file from Github. Here are the commands I used on my Raspberry Pi to accomplish this:

Install AVRDUDE with the command apt-get install avrdude
Download the file: wget raw.githubusercontent.com/mobilinkd/tnc1/arduino/images/mobilinkd-473-arduino.hex
Connect the Nano to a USB port and run the command dmesg | grep ttyUSB* to discover the USB port connected to the Nano (probably  ttyUSB0).
From the same directory that you downloaded the HEX file, run the command:
avrdude -p m328p -c arduino -P /dev/ttyUSB0 -b 57600 -F -U flash:w:mobilinkd-473-arduino.hex
Your Nano should now be an APRS KISS TNC.

The Nano TNC communicates with the Bluetooth at a baud rate of 38400,8,N,1 but the default communications baud rate of the HC-05 module is 9600. To change this and optionally change the Bluetooth's Name and Password, see http://www.martyncurrey.com/arduino-with-hc-05-bluetooth-module-at-mode/ for a tutorial on changing these parameters. The AT command to change the baud rate is AT+UART=3800,1,0
Note: AT+UART=<Param>,<Param2>, <Param3> (Param1: Baud, Param2: Stop bit, Param3: Parity) see https://www.itead.cc/wiki/Serial_Port_Bluetooth_Module_(Master/Slave)_:_HC-05

The last component is a Smartphone running APRSdroid. The are many tutorials on the web for configuring APRSdroid to interface via Bluetooth a KISS TNC.