TNC Modem - APRS with an old smart phone, arduino, and a hand held radio

I am building a slightly modified version of the Micro Modem by Mark Quist (http://unsigned.io/projects/micromodem/). My goal are to adapt the circuit to be used with an Arduino Nano driving a Baofeng UV-82. Then hookup an old android phone to the tnc modem and use the ARPdroid app to send and receive ARPS positions and messages.

Pre-build firmware for the atmega328p chip (which the Arduino Nano uses) can be found in at https://github.com/markqvist/MicroAPRS/tree/master/precompiled. One can also build the firmware from source, which is required for Arduino boards with different microprocessors. In that case check the Makefile and device.h have the desired configuration.

Windows OS Notes

• Uploading firmware to the Arduino:
Use ArduinoSchetchUploader (https://github.com/christophediericx/ArduinoSketchUploader) to upload the firmware (aka sketch).
• Compiling Arduino firmware:
Use WinAVR (http://winavr.sourceforge.net/) to build the firmware from source using make clean all command.

Current Issues

• Sending ARPS:
Sometimes sent ARPS message are not received by my local iGate or other nodes in the neighbourhood. I'm not sure if there is a setup issue or APRS is naturally that flaky.
• Receive ARPS message:
ARPS messages don't seem to be received. I'm not sure if that's a hardware or software issue.