Hi,

this page will get You the documentation on how to setup svxlink echolink node on RPi2 with linux and control radio via GPIO port.
Note: documentation on svxlink installation & configuration, raspbian linux installation, configuring Alinco & programming GM300 is beyond the scope of this article.

So let’s get started 🙂

I have been requested by YU1PCD to build an echolink node based on RPi and linux.
We have agreed that we build it with Alinco DJ196 portable radio station since it met requirements.
Requirements: COR Active HIGH signal. (this is so interface and svxlink knows when squelch is open in order not to use VOX for squelch detection. It’s cleaner, easier and safer)
Later on, we have found so it would work much better with Motorola GM300 so we made changes on the radio control interface. Whole process is explained in the following text…

First, we got ourselves an RPi Model B 2 V1.1.
Then, we flashed an RASPBIAN JESSIE downloaded from: https://www.raspberrypi.org/downloads/raspbian/

Flashed image with linux.
Installation instructions can be found on:
https://www.raspberrypi.org/documentation/installation/installing-images/README.md

Next, we setup svxlink software.
Download and installation instructions & configuration documentation:
http://www.svxlink.org/
https://github.com/sm0svx/svxlink/wiki/InstallSrcHwRpi

Next we setup USB soundcard. For audio levels testing use alsamixer software.

Next, we setup GPIO pins.
We needed one output pin for PTT signal, one input for COR signal (plus one pin constantly active, schematic explaines later why), and one pin for the ground.
Total of four GPIO pins.

Which GPIO pins You will use depends up to You and it is best to find pinout of particular PRi You will use.
Almost all pins can be programmed to be either input or output, except some fixed pins, i.e. V+, ground… etc.

So, this is the schematic for svxlink interface for Alinco DJ-196.
SVX-DJ196_Interface_schem

And here it is in action:

Later on we have found out that Alinco has some problems when connected to external antenna :/
So we have decided to switch to Motorola GM300 radio.

In order to get COR signal (in motorola also known as CSQ) you either need to program GM300 pin 8 to CSQ ACTIVE HIGH
if You have a 16CH unit. Or if You have 8CH unit it should be enabled by default on pin 8.
DO NOT take this for granted, I do not have experience with these radios. But, either way, You need CSQ ACTIVE HIGH enabled somehow.

We have used a 16CH unit and pins used on ACC connector are:
PIN 2: MIC INPUT
PIN 3: PTT
PIN 7: GROUND
PIN 8: CSQ (ACTIVE HIGH)
PIN11: RX AUDIO

In order for this interface to work with GM300 following modifications on interface needed to be done.
Interface-GM300_schem

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