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We want to make a TNC system with Arduino Uno.
This system will apply to OSSI APRS Kit
We use VX-2R for transmitter, IC-T70E for receiver and Arduino Uno for TNC.
We used BeRTOS to make TNC. But we've modified little as the original BeRTOS uses Arduino Duemilanove.
Developing Environment is Ubuntu 11.10 64bit Version.
We refer follow sites : BeRTOS Official Site, BeRTOS ArduinoHowto
From that reference we change something.
In schematic, number of connector pin is changed from 4 to 3, but still use 4 pole connector. Because, radios usually don't get PTT input by connector and just use VOX system.
For that reason, we connect PTT and MIC IN with 2K resistor

Hardware Setting

Schematic of Arduino APRS


In original schematic, there are two VCCs. They are different VCCs. The one connected with arduino is 9V or some other Vin Voltage and another one is 5V from arduino 5V Vout.( do NOT connect to 3.3V as audio signal is biased to 2.5V and analyzed based on the bias point)

arduinobreadboard.jpg We connect like above picture.
We use a 100k variable resistor instead of 50k(R6).
We also use 2N2222A transistor instead of BC547(T1).
We connect MIC IN port and PTT port with 2k resistor, because the connector of radios what we use is just have GND, Sound and MIC.
When making connector check your radio’s PTT structure and connector’s GND, Sound, MIC(, PTT).

Usually 4-pole-connector and 3-pole-connector interface is like above.
Ordinary 4-pole-connector and VX-2R's connector is little different.
In VX-2R's case, connect pin 1 of JP1 and one of surround sound output, pin 2 and MIC input, pin 3 and Ground.

Some radios apply above type of connector.(ex : IC-T70E)
At that time connect pin 1 of JP1 and one of surround sound output(or mono sound output), pin 2 and one of surround MIC input(or mono MIC input), pin 3 and both grounds.
Check your own radio connector's spec and connect with each pins.

Make two of this module for transmitter and receiver

Software Setting

Download BeRTOS

Extract downloaded file

Install necessary programs

$ sudo apt-get install python-qt4 libqt4-dev
$ sudo apt-get install build-essential
$ sudo apt-get install avr-libc
$ sudo apt-get install avrdude

Run wizard

in extracted directory(ex : $ cd ~/Download/bertos-2.7.0)

$ ./wizard/

Compile and upload

in created project directory(ex : $ cd ~/Arduino_AVR)

$ make clean
$ make
$ avrdude -p m328p -c arduino -P /dev/ttyACM0 -b 115200 -F -U flash:w:images/Arduino_AVR.hex


before do avrdude check your environment with above image


Install cutecom

$ sudo apt-get install cutecom
$ cutecom

Setup like above and click open device button

Setup radios

Makes two radios frequency same icfreq.jpg vx2freq.jpg

Get the message


Sometime wizard makes crash.
Or need reset.
At that time you need to delete configure file of wizard

$ rm ~/.config/Develer/Bertos\ Configurator.conf
balloon/tnc.txt · Last modified: 2012/01/25 16:04 by ossi