Raspberry Pi Audio Receiver

A simple, light weight audio receiver with Bluetooth (A2DP), AirPlay 2, and Spotify Connect.

Features

Devices like phones, tablets and computers can play audio via this receiver.

Requirements

• A USB Bluetooth dongle (the internal Raspberry Pi Bluetooth chipset turned out as not suited for audio playback and causes all kinds of strange connectivity problems)
• Raspberry Pi OS 12 Lite
• Internal audio, HDMI, USB or I2S Audio adapter (tested with Adafruit USB Audio Adapter, pHAT DAC, and HifiBerry DAC+)

Again: do not try to use the internal Bluetooth chip, this will only bring you many hours of frustration.

Installation

The installation script asks whether to install each component.

wget https://raw.githubusercontent.com/nicokaiser/rpi-audio-receiver/main/install.sh
bash install.sh

Note: the installation process is not reversible, there is no uninstall. The script is meant to be run on a clean device that is not used for anything else.

Basic setup

Lets you choose the hostname and the visible device name ("pretty hostname") which is displayed as Bluetooth name, in AirPlay clients and in Spotify.

Bluetooth

Sets up Bluetooth, adds a simple agent that accepts every connection, and enables audio playback through ALSA. A udev script is installed that disables discoverability while connected.

AirPlay 2

Installs Shairport Sync AirPlay 2 Audio Receiver.

Spotify Connect

Installs Raspotify, an open source Spotify client for Raspberry Pi.

Additional steps

Enable HiFiBerry device

When using a HiFiBerry or similar I2C device, a device tree overlay needs to be enabled in /boot/firmware/config.txt (replace dacplus with the overlay that fits your hardware):

...
dtoverlay=hifiberry-dacplus

To enable the software volume mixer, /etc/asound.conf needs to be created:

defaults.pcm.card 0
defaults.ctl.card 0

pcm.hifiberry {
  type hw
  card 0
  device 0
}
pcm.dmixer {
  type dmix
  ipc_key 1024
  ipc_perm 0666
  slave.pcm "hifiberry"
  slave {
    period_time 0
    period_size 1024
    buffer_size 8192
    rate 44100
    format S32_LE
  }
  bindings {
    0 0
    1 1
  }
}
ctl.dmixer {
  type hw
  card 0
}
pcm.softvol {
  type softvol
  slave.pcm "dmixer"
  control {
    name "Softvol"
    card 0
  }
  min_dB -90.2
  max_dB 0.0
}
pcm.!default {
  type plug
  slave.pcm "softvol"
}

Read-only mode

To avoid SD card corruption when powering off, you can boot Raspberry Pi OS in read-only mode. This can be achieved using the raspi-config script (in the "Performance" section).

Disable Wi-Fi power management

Disabling Wi-Fi power management might resolve some connection issues:

sudo nmcli connection modify preconfigured wifi.powersave 2

Disable internal Bluetooth and Audio

When an external audio device (HDMI, USB, I2S) is used, the internal audio can be disabled in /boot/firmware/config.txt (replace hifiberry-dacplus with the overlay which fits your installation):

...
dtoverlay=disable-bt
dtparam=audio=off
dtoverlay=vc4-kms-v3d,noaudio
dtoverlay=hifiberry-dacplus

Add Bluetooth devices

The device should be visible for new Bluetooth connections, but in some cases you might need to pair them manually:

sudo bluetoothctl
power on
agent on
# Now search for available bluetooth devices from your device
# Once paired note down the MAC address of your device 
trust 00:00:00:00:00:00 # Put device MAC address here so after reboot it can automatically re-connect again

Disable Wi-Fi when Bluetooth is connected

Dislaimer: You really might want to use a Bluetooth USB dongle. The internal Bluetooth module of the Raspberry Pi (all versions) is very limited and using it for audio transmission will most certainly lead to problems and unexpected behaviour, see raspberrypi/linux/#1402.

If you really want to use the internal Bluetooth module, you almost certainly need to disable Wi-Fi.

Modify /usr/local/bin/bluetooth-udev and remove the comments (#) around the ifconfig calls:

...
if [ "$action" = "add" ]; then
    ...
    # disconnect wifi to prevent dropouts
    ifconfig wlan0 down &
fi

if [ "$action" = "remove" ]; then
    # reenable wifi
    ifconfig wlan0 up &
    ...
fi

Bluetooth A2DP volume

To enable A2DP volume control, add the --plugin=a2dp parameter to the bluetoothd command line. This helps setting the volume via Bluetooth, but does not work on all setups.

# Enable A2DP volume control
mkdir -p /etc/systemd/system/bluetooth.service.d
cat <<'EOF' > /etc/systemd/system/bluetooth.service.d/override.conf
[Service]
ExecStart=
ExecStart=/usr/libexec/bluetooth/bluetoothd --plugin=a2dp
EOF

Bluetooth Fast Connectable

Using the FastConnectable flag may lead to faster Bluetooth connections, but may also lead to poor sound quality. You can try and see if it works for you. See #70

Add the flag to the General section in /etc/bluetooth/main.conf:

[General]
...
FastConnectable = true
...

Bluetooth pairing with PIN

To enable pairing with a PIN code instead of Simple Secure Pairing mode, the following steps are required:

1. Change sspmode 1 to sspmode 0 in /etc/systemd/system/[email protected]
2. Add --pin /etc/bluetooth/pin.conf to the ExecStart line in /etc/systemd/system/[email protected]
3. Add a file /etc/bluetooth/pin.conf which contains PIN code for the devices:

AA:BB:CC:DD:EE:FF 1234 (replace AA:BB:CC:DD:EE:FF with your Bluetooth devices's Mac address or * to use PIN 1234 for all devices)

Notes

• This does not work with iOS devices. iOS refuses to pair with devices that do not support SSP. So sspmode needs to be on
• Even with sspmode=1 and a PIN file, iOS would not connect at all
• macOS allows pairing with devices with sspmode=0 (and a PIN configured on the Pi). When sspmode=1, macOS decides upon a PIN and either the Pi has a fixed PIN list (which does not match => connection refused), or requires keyboard input on the Pi (which is not desired for a headless device).

So you need to try yourself if this works with your setup.

Limitations

• Only one Bluetooth device can be connected at a time, otherwise interruptions may occur.
• The device is always open, new clients can connect at any time without authentication.
• To permanently save paired devices when using read-only mode, the Raspberry has to be switched to read-write mode until all devices have been paired once.
• You might want to use a Bluetooth USB dongle or have the script disable Wi-Fi while connected (see bluetooth-udev), as the BCM43438 (Raspberry Pi 3, Zero W) has severe problems with both switched on, see raspberrypi/linux/#1402.
• The Pi Zero may not be powerful enough to play 192 kHz audio, you may want to change the values in /etc/asound.conf accordingly.

Disclaimer

These scripts are tested and work on a current Raspberry Pi OS setup on Raspberry Pi. Depending on your setup (board, configuration, sound module, Bluetooth adapter) and your preferences, you might need to adjust the scripts. They are held as simple as possible and can be used as a starting point for additional adjustments.

Upgrading

This project does not really support upgrading to newer versions of this script. It is meant to be adjusted to your needs and run on a clean Raspberry Pi OS install. When something goes wrong, the easiest way is to just wipe the SD card and start over. Since apart from Bluetooth pairing information all parts are stateless, this should be ok.

Updating the system using apt-get upgrade should work however.

Contributing

Package and configuration choices are quite opinionated but as close to the Debian defaults as possible. Customizations can be made by modifying the scripts, but the installer should stay as simple as possible, with as few choices as possible. That said, pull requests and suggestions are of course always welcome. However I might decide not to merge changes that add too much complexity.

Related projects

There are many forks and similar projects that are optimized for more specific requirements.

• Arcaria197/rpi-audio-receiver - a fork that uses Raspbian 10 (legacy) and runs on Raspberry Pi Zero W hardware
• HiFiBerryOS - a more sophisticated approach on this, using an entirely custom (buildroot) ecosystem

References

• Shairport Sync: AirPlay 2 audio player
• Raspotify: A Spotify Connect client that mostly Just Works™

License

MIT