Raspberry Pi Bluetooth Speaker
How To Build a Raspberry Pi Bluetooth Speaker
This articles describes how to build a Bluetooth speaker. This article is being actively written. Currently it is full of bugs but will provide some useful pointers.
Before You Start
- A Raspberry Pi
- A Bluetooth USB dongle (if your Pi doesn’t have Bluetooth on board)
- Sound card and speaker(s)
- Test everything
- Turn every background task into a service
- More investigation on Bluetooth pairing
Getting the Speaker(s) Working
To get the best results, you'll need an dedicated audio add-on board and matching speakers. Higher end passive speakers need a proper amplifier (e.g. HiFiBerry Amp2 or IQaudIO IQaudIO DigiAMP+).
I've used the whole range of IQaudio audio boards with different speakers and headphones. I'd also recommend a dedicated USB Bluetooth dongle (don't get the cheapest versions of these). It is possible to test by using the on-board Bluetooth and the on-board audio with headphones but the audio quality, owing to dropped packets, isn't great.
Once the speakers and audio card and all connected to the Raspberry Pi, it's time to install a fresh version of Alpine Linux. The armv7 version from the Downloads page works on almost all Pis. This Wiki has several articles about installing Alpine on a Raspberry Pi.
Enable writing to the boot media:
mount /media/mmcblk0p1 -o rw,remount
Then either enable the on board sound:
echo "dtparam=audio=on" >> /media/mmcblk0p1/usercfg.txt
or your fancier sound card (e.g. IQaudIO):
echo "dtoverlay=iqaudio-dacplus,unmute_amp" >> /media/mmcblk0p1/usercfg.txt
and then reboot your Pi.
Follow these instructions to enable ALSA. In summary
apk add alsa-utils alsa-utils-doc alsa-lib alsaconf # the required software for sound aplay -l # should display a List of PLAYBACK Hardware Devices
In my case my list is:
**** List of PLAYBACK Hardware Devices **** card 0: Headphones [bcm2835 Headphones], device 0: bcm2835 Headphones [bcm2835 Headphones] Subdevices: 8/8 Subdevice #0: subdevice #0 Subdevice #1: subdevice #1 Subdevice #2: subdevice #2 Subdevice #3: subdevice #3 Subdevice #4: subdevice #4 Subdevice #5: subdevice #5 Subdevice #6: subdevice #6
Before you play anything from your speakers, I advise you to lower the volume first.
displays a list of "simple controls"; for my headphones and the on-board sound, the output is this:
Simple mixer control 'Headphone',0 Capabilities: pvolume pvolume-joined pswitch pswitch-joined Playback channels: Mono Limits: Playback -10239 - 400 Mono: Playback 0 [96%] [0.00dB] [on]
In this case there is only 1 control, 'Headphone', so I issue this command to lower the maximum volume to a comfortable level (50% in my case).
amixer sset Headphone 50%
The IQaudIO DAC that I use has a much longer set of controls. I issued this command to set the volume:
amixer sset 'Digital' 50 # quotes may be required if there are spaces in the control name
Note that there can be several interlinked controls, some of which are muted by defualt. ALSA (and other audio software on Linux) is notoriously under-documented, try `man amixer` for more information. Sometimes it is easier to use a more visual control to change the configuration:
Finally, if you issue this command:
speaker-test -t wav -c 2
Then you should hear "Front Left, Front Right" repeating from your chosen speakers. Now it's time to setup Bluetooth. Don't forget to save your changes (lbu commit) before moving on.
I used Raspberry Pi 3 - Setting Up Bluetooth as a reference with some slight modifications as I am using a Pi 4.
Raspberry Pi 4
apk add bluez btattach -B /dev/ttyAMA0 -P bcm -S 3000000 & # btattach -B /dev/ttyAMA0 -P bcm -S 115200 -N & # Pi 3 - not tested by me rc-service bluetooth start
edit /etc/mdev.conf and enable bluetooth. We're using `sed`, where s/#rpi bluetooth/rpi bluetooth/ means replace #rpi bluetooth with rpi bluetooth.
sed -i 's/#rpi bluetooth/rpi bluetooth/' /etc/mdev.conf sed -i 's/#ttyAMA0 root:tty 660 @btattach -B \/dev\/$MDEV -P bcm -S 115200/ttyAMA0 root:tty 660 @btattach -B \/dev\/$MDEV -P bcm -S 3000000/' /etc/mdev.conf
Note: the last command uncomments the btattach command and changes it to work with the Pi 4.
Changes to /etc/bluetooth/main.conf
Name = Pi-Bluetooth-Speaker # This is what you'll see when connecting Class = 0x41C # Adding audio playback and recording to this Bluetooth device DiscoverableTimeout = 0 # Always discoverable AlwaysPairable = true # Always pairable PairableTimeout = 0 # no time limit AutoEnable=true # starts Bluetooth when Linux 'sees' the Bluetooth device at boot
Ensure that Bluetooth is started at boot:
rc-update add bluetooth
Bluetooth's state, including paired devices, in held in /var/lib/bluetooth so you'll need to add this to `lbu` state:
lbu include /var/lib/bluetooth lbu commit && reboot
Manual device pairing
[bluetooth]# discoverable on [agent] Confirm passkey 627133 (yes/no): yes [agent] Authorize service 0000110e-0000-1000-8000-00805f9b34fb (yes/no): yes
apk add python3 py3-dbus py3-gobject3
Getting this to work currently involves running the bluez-simple-agent after having edited it to always return sucessful. You'll need to comment out some lines (by adding "#" at the beginning):
def RequestConfirmation(self, device, passkey): #print("RequestConfirmation (%s, %06d)" % (device, passkey)) #confirm = ask("Confirm passkey (yes/no): ") #if (confirm == "yes"): set_trusted(device) return #raise Rejected("Passkey doesn't match")
And then running the revised agent in the background, and pair your devices:
bluez-simple-agent & lbu include /usr/bin/bluez-simple-agent lbu commit
At the time of writing this article, bluez-alsa is only found in the community repositories, so you need to edit your repository list:
remove the "#" from the community repository, mine is:
This is the final stretch. We've got bluetooth working and now we want to link bluetooth to the speakers
apk add bluez-alsa bluealsa -p a2dp-source -p a2dp-sink & bluealsa-aplay &
Raspberry Pi's blog on How to play sound and make noise with your Raspberry P
There are lots of speaker and amplifier options:
- Raspberry Pi's IQaudIO boards
- Pimoroni's Audio Amp SHIM (3W Mono Amp) and Mini Speaker 4Ω (3W)
- The Pi Hut offers this Adafruit I2S 3W Stereo Speaker Bonnet for Raspberry Pi (Mini Kit) and the Stereo Enclosed Speaker Set - 3W 4 Ohm