Hi,
this page describes using microAPRS firmware on Arduino Nano V3.0 with APRSdroid via USB serial connection for sending and receiving APRS AX25 packets. Please read entire page first before making any steps!

APRSdroid is a great android application for sending and receiving APRS AX25 packets. It is developed by Georg Lukas DO1GL, and contributed by many others. You can find all the information about this application
on http://aprsdroid.org

Recently, Georg has added USB serial support for TNC so I decided to make that kind of TNC. (for the USB support in app You need to download APK from builds dir on his website, still in beta)

If You would like to support application’s further development You can buy app directly on Google Play (for android users).

Arduino Nano V3.0 was my hardware of choice for the TNC because of the built-in FTDI FT232 USB chip and it’s small dimensions. All information about this ATMEGA328 based board can be found on https://www.arduino.cc/en/Main/ArduinoBoardNano

microAPRS is an APRS firmware written by Mark Qvist OZ7TMD and all information about this great opensource firmware are on his website http://unsigned.io/projects/microaprs/ where You can also buy microAPRS hardware with installed software directly on his webshop!

All tied up together.

First, I flashed my TNC with microAPRS set in KISS mode.

I have connected the TNC with android device using USB OTG cable, android device asked if I wish to use USB connection with APRSdroid, I say YES, of course. Then, in APRSdroid app, I choose “USB serial” under “Connection protocol“, although it should already be selected. Under “Connection preferences” I’ve set baud rate to 9600 (8N1 control is the default).

NOTICE: Apparently some android devices DO NOT have OTG support so this setup might not work with every android device! I have tried to use this with my CAT B15 phone and it does not work!

IMG_0521

Arduino Nano V3.0 running microAPRS and built according to Mark Qvist scheme.

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Notice that I am using Baofeng HT which has builtin de-emphasis filter so in order to raise decoding rate of packets (if You use Baofeng) You should probably apply a highpass RC filter which I have not applied here. (I probably should and will)
Edit: I did! And it improved decoding a lot!

It’s really up to Your specific case and a great source of information on this and other subjects related to microAPRS can be found on Mark Qvist’s forum on his website http://unsigned.io/forum/

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All tied up together.

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APRSdroid raw packets view.

IMG_0525

Packet seen on http://aprs.fi

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