Skip to content
Automatic switch to analog FM with MMDVM
Branch: master
Clone or download
Fetching latest commit…
Cannot retrieve the latest commit at this time.
Type Name Latest commit message Commit time
Failed to load latest commit information.


First check if your RX TX are ready for FM. Here i have ft7800 TX and FT857d as RX.

You must have a Piface card from JoyIt a USB Soundcard and Alsa utilitys are running. The WiringPi must be installed also the WiringPiDev librarys

One of the relais switch off the PTT from MMDVM to TX, digitalWrite (RELAIS1, HIGH) ;. The second switch off the sound from MMDVM to TX. digitalWrite (RELAIS2, HIGH)

digitalWrite (PTT, HIGH) set PTT from Mic input at the TX.

The audio path for FM is from RX out to USB Card Mic and from USB Card sound out to mic in from the TX unit. In this constelation it is possible to mix other sounds to the audio path as shown at the software. At the FT7800 this audio Path only works with Mic in PTT !!!!!!!!!!!!!!!!!!!!!!!! So there is no problem to switch back to digital sound from MMDVM

Compiler command

gcc -Wall relais.c -o relais -lwiringPi -lwiringPiDev

More details are following

schematics.jpg gives a overview how to connect raspi, mmdvm, piface and usb soundcard

at you can find a description piface

relais without a extension is the binary

This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version. This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with this program. If not, see

You can’t perform that action at this time.