Raspberry Pi Bluetooth speakers

Hello everyone,

I recently uploaded a video to share more detail on how I turned a Raspberry Pi into a custom Bluetooth speaker for my carpc project. I thought it would be cool to share a step-by-step description of the entire project. Enjoy!

In this post I'll assume you have a Raspberry Pi 2B with a working installation of Raspbian Stretch, a USB Bluetooth dongle, and a speaker. Start by updating the Pi and running some preparatory commands in a console.

sudo apt-get update
sudo apt-get dist-upgrade -y
sudo rpi-update
sudo poweroff

Restart the Pi and install all needed packages for Bluez and PulseAudio.

sudo apt-get install bluez pulseaudio-module-bluetooth python-gobject python-gobject-2

Add the active user to the lp group.

sudo usermod -a -G lp pi

Edit the Pulseaudio daemon configuration file and change the resampling method to trivial. In my file, the relevant configuration line was present but commented out.

sudo vim /etc/pulse/daemon.conf
    >> resample-method = trivial

Enable required functionality of the Bluetooth module by adding the following line to the General section of the Bluetooth main configuration file.

sudo vim /etc/bluetooth/main.conf
    >> Enable=Source,Sink,Media,Socket

Now reboot.

sudo reboot

Activate the Bluetooth service and verify that the adapter is recognized as hci0 by hciconfig.

sudo service bluetooth start
sudo service bluetooth status
sudo hciconfig -a

Activate the Bluetooth on your phone, and run a device scan on the Pi. Take note of the Bluetooth address of your phone (XX:XX:XX:XX:XX:XX). Then, add the piscan option to hciconfig, and verify that a line saying "UP RUNNING PSCAN ISCAN" in all caps is present in the output of hciconfig -a. When you are set, run the bluetoothctl agent.

sudo hcitool scan
sudo hciconfig hci0 piscan
sudo hciconfig -a
bluetoothctl

Now go to your phone and pair it with the Pi. You may be asked to provide a PIN of your choice. The bluetoothctl agent will ask you to provide the same PIN to greenlight the operation. If successful, authorize the two services proposed by bluetoothctl (multimedia and audio calls), and run the following commands in the bluetoothctl prompt to tell Bluez you trust your phone.

agent on
default-agent
trust XX:XX:XX:XX:XX:XX
quit

Excellent. now we need to identify possible data sources, data sinks, and connect the Bluetooth source to the audio sink. Take note of the Bluez source and of the complete name of the default sink as returned by pactl. Use the two strings as "source" and "sink" arguments to "pactl load-module module-loopback".

pactl list sources short
pactl list sinks short
pactl load-module module-loopback source=bluez_source.XX_XX_XX_XX_XX_XX.a2dp_source sink=alsa_output.platform-soc_audio.analog-stereo
# For source and sink, use the relevant output of the two relevant pactl list commands, and your phone address.

The last step is to redirect all HDMI audio to the jack, and to pump the volume up.

amixer cset numid=3 1
amixer set Master 100%
pacmd set-sink-volume 0 65537

From this moment on, all audio produced by your phone, including music, ringtones, alarms, and voice calls, is played by the speaker connected to the Raspberry Pi. The audio source can be any Bluetooth-capable device. The pin-based authentication step is done only once. After that, the device is trusted and pairing does not require any human action on the Pi.

So, this is how I turned a Raspberry Pi into a Bluetooth speaker for my carpc project. It was good fun, and I encourage you to play around with Bluetooth communication on your devices. Bluetooth is so widely spread and supported, and it is a good option for low-bandwidth wireless communication between DIY projects and commercial devices.

Have you ever worked with Bluetooth? Have you ever made something cool with it? Share your experience!

Have fun,
Kradion.