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 because of dropped packets, the audio quality isn't great.
Once the speakers and audio card are 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 sound card (e.g. IQaudIO):
echo "dtoverlay=iqaudio-dacplus,unmute_amp" >> /media/mmcblk0p1/usercfg.txt
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 recommend turnong down the volume.
displays a list of "simple controls." For my headphones and the on-board sound, the output looks like 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%)
amixer sset Headphone 50%
The IQaudIO DAC that I use has a much larger 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: 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).
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