This gist will show how to setup Raspbian Stretch as a headless Bluetooth A2DP audio sink. This will allow your phone, laptop or other Bluetooth device to play audio wirelessly through a Rasperry Pi.

A quick search will turn up a plethora of tutorials on setting up A2DP on the Raspberry Pi. However, I felt this gist was necessary beacuse this solution is:

• Automatic & Headless - Once setup, the system is entirely automatic. No user iteration is required to pair, connect or start playback. Therefore the Raspberry Pi can be run headless.
• Simple - This solution has few dependencies, readily available packages and minimal configuration.
• Up to date - As of December 2017. Written for Raspbian Stretch & Bluez 5.43

• Raspberry Pi - I used the Raspberry Pi 3. The Pi 3 has integrated Bluetooth, however there is a known bug when the WiFi is used simultaneously.
• Raspbian Stretch Lite - See the offical guide on how to install the latest Raspbian OS: https://www.raspberrypi.org/learning/software-guide/quickstart/

If you are using a separate USB Bluetooth dongle, disbale the integrated Bluetooth to prevent conflicts.

To disable the integrated Bluetooth Add the

# Disable onboard Bluetooth
dtoverlay=pi3-disable-bt

to /boot/config.txt and execute the following command

sudo systemctl disable hciuart.service

First execute the following commands to make sure the system is up to date.

sudo apt-get update
sudo apt-get upgrade

Then reboot the Pi to ensure the latest kernal is loaded.

Now install the pre-requisite packages.

sudo apt-get install bluealsa python-dbus

Normally a Bluetooth device is only discoverable for a limited amount of time. Since this is a headless setup we want the device to always be discoverable.

• Set the DiscoverableTimeout in /etc/bluetooth/main.conf to 0

# How long to stay in discoverable mode before going back to non-discoverable
# The value is in seconds. Default is 180, i.e. 3 minutes.
# 0 = disable timer, i.e. stay discoverable forever
DiscoverableTimeout = 0

• Enable discovery on the Bluetooth controller

sudo bluetoothctl
power on
discoverable on
exit