Build an open source fm radio station with your raspberry pi
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FMBerry Logo FMBerry

Written by Tobias Mädel (

What is this?

FMBerry is a piece of software that allows you to transmit FM radio with your Raspberry Pi.


How does it work?

It uses the Sony-Ericsson MMR-70 transmitter, which was originally intended for use with Sonys Walkman cellphones from early 2000s. You can get these for really cheap from Amazon.

If you can't seem to get one, contact me via Mail (, I managed to get hold of quite a lot of these transmitters.

What do I need to build this?

  • MMR-70 transmitter
  • Raspberry Pi (compatible & tested with every Pi, Model Beta, A, B, B+, 2, Zero, 3)
  • Soldering equipment (soldering iron and some solder)
  • Cable for connecting to your Raspberry Pis GPIO port (old IDE cable does work fine!)

The hardware is explained here:


This software was developed under Raspbian Wheezy 2013-02-09.

Arch Linux users: AUR - fmberry-rpi-git

Step 1: Enabling I²C

Open raspi-blacklist.conf:

sudo nano /etc/modprobe.d/raspi-blacklist.conf

Comment out the Line "blacklist i2c-bcm2708" with a #. Save with Ctrl+O and close nano with Ctrl+X

To make sure I²C Support is loaded at boottime open /etc/modules.

sudo nano /etc/modules

Add the following lines:


Then again, Save with Ctrl+O and then close nano with Ctrl+X.

Please reboot your Raspberry after this step.

Step 2: Installing I²C tools and dependencies for the build

First update your local package repository with sudo apt-get update

then install all needed software with the following command: sudo apt-get install i2c-tools build-essential git libconfuse-dev

Step 3: Finding out your hardware revision

Run cat /proc/cpuinfo | grep "CPU revision" in your terminal.

All Raspberry Pi's with a revision newer than rev. 2 have their i2c port connected up to /dev/i2c-1.

Older devices (beta, alpha, early 256MB Model B's) have it connected up to /dev/i2c-0.

Step 4: Checking the hardware

You can check your wiring with the following command:

i2cdetect -y 1

Please remember that you need to run the command on another port on older revisions!

i2cdetect -y 0

You should then see your transmitter at 0x66.

If you are not able to see your transmitter please double check your wiring!

If you connect you MMR-70 to I²C bus 0 on Raspberry Pi rev2 make sure that header P5 pins are configured as I²C pins!

Output of i2cdetect

Step 5: Building the software

To build the software execute the following commands (in your homefolder):

git clone
cd FMBerry

If you have got an old revision board, please open fmberryd.c and change the RPI_REVISION definition to RPI_REV1!


Compiling the software will take a couple of seconds.

Step 6: Installing the software

FMBerry is essentially a daemon called fmberryd. To install it into your system path type sudo make install.

You can start it by typing sudo /etc/init.d/fmberry start.

To control the daemon you have to use ctlfmberry.

It currently allows the following commands:

  • ctlfmberry set freq 99000 - Frequency in kHz (76000 - 108000)
  • ctlfmberry poweron
  • ctlfmberry poweroff
  • ctlfmberry set rdsid DEADBEEF (8 chars! Longer strings will be truncated, shorter - padded with spaces)
  • ctlfmberry set rdstext Mike Oldfield - Pictures in the Dark (max. 64 chars. Longer strings will be truncated)
  • ctlfmberry set txpwr 0 - 0.5 mW Outputpower
  • ctlfmberry set txpwr 1 - 0.8 mW Outputpower
  • ctlfmberry set txpwr 2 - 1.0 mW Outputpower
  • ctlfmberry set txpwr 3 - 2.0 mW Outputpower (Default.)
  • ctlfmberry stereo on - Enables stereo signal (Default)
  • ctlfmberry stereo off - Disables stereo signal
  • ctlfmberry muteon - Mute audio
  • ctlfmberry muteoff - Unmute audio
  • ctlfmberry gainlow - Audio gain -9dB
  • ctlfmberry gainoff - Audio gain 0dB"
  • ctlfmberry set volume 0-6 Audio volume level 0 to 6, equal -9dB to +9db, 3dB step
  • ctlfmberry status - Print current status
  • ctlfmberry stop - Stop FMBerry daemon

That's it! :)

Step 7: Debugging

FMBerry writes debugging output to /var/log/syslog.

You can watch the information by running ctlfmberry log. It's essentially just a cat /var/log/syslog | grep fmberryd

It will tell you what's wrong.

Updating the software

Please check for new dependencies. You can safely just run the apt-get install command again. It will only install new dependencies if necessary.

First stop the daemon by typing /etc/init.d/fmberry stop.

Then run git pull followed by a make and a sudo make install.

You can then start FMBerry again with /etc/init.d/fmberry start.


  • WARNING! I am not a professional C programmer. Please expect this software to have major security flaws. Please don't expose it's control port to the internet! I'm fairly certain that this software is vulnerable to buffer overflows.

  • If you are a C programmer, please help by securing this software and sending a pull request.

  • The Daemon itself is essentially a simple TCP server. It is listening to Port 42516. (set in fmberry.conf) You can control it by sending the exact same commands you would give to ctlfmberry.

  • For information on How to control the Daemon have a look into ctlfmberry. It's a simple shell script.

  • Feel free to contact me: (english and german)

Projects using FMBerry (streaming of MPD title data via RDS) (streaming of internet radio streams, controllable via Webinterface) (enabling the LED on the transmitter to be software controllable)

Common problems

The daemon does not show anything.

That's normal. You have to use ./ctlfmberry to control the daemon.

I can't seem to hear music.

Turn up the volume/unmute your raspi with alsamixer.

I am getting compile errors.

Did you install all dependencies? (All lines with apt-get)

The transmission dies after a couple of minutes.

You didn't disable the internal processor of the MMR70. Do this by connecting TP18 to GND.

The power supply of the raspberry pi shorts out/there are no lights anymore_

There is a short circuit. Probably caused by a wiring fault or by using an 80pin IDE cable for connecting the FMBerry.

Alternative linux distributions don't detect the I2C bus (ArchLinux, OpenWRT, OSMC)

Linux 3.18 introduced a new feature called Device Tree support. To get the I²C Bus working, you need to put this configuration at the end of /boot/config.txt (change the first parameter according to the RPi you have):


Thanks to Daniel for the solution to that problem!