Example Bluetooth tasks using the Python PyBluez module. Tested using BlueZ 5 on:

• Raspberry Pi 2 with CSR bluetooth 4.0 USB adapter
• Raspberry Pi 3 / 4 (on-board Bluetooth)
• laptop with Ubuntu
• Windows (Bluetooth classic, non-BLE only)

For Ubuntu <= 18.04 we use system Python 2.7 for ease of library install. If you have Anaconda/Miniconda, you can alternatively use conda-forge libraries.

1. from Terminal:

   apt install python-pip python-bluez libbluetooth-dev libboost-python-dev libboost-thread-dev libglib2.0-dev bluez bluez-hcidump
   
   adduser lp $(whoami)

2. setup Python code:

   python -m pip install -e .

3. check that your Bluetooth devices are not blocked (should say "no"):

   rfkill list

python bluetooth_scan.py

If no Bluetooth devices found in the PyBluez device scan, try each of the following:

hcitool scan

and:

bluetoothctl

scan on

If the second way finds devcies but not the first, you may have a chipset issue. I have noted this with Marvell hardware on Ubuntu 18.04. I did not look into a resolve for this, as I usually use other hardware.

If you get error

OSError: No such device

check that there is a Bluetooth adapter available:

hciconfig dev

The bluetooth adapter may need to be enabled:

hciconfig hci0 up

These example use Bluez directly from Terminal (without Python)

using Bluez5 bluetoothctl agent:

hciconfig hci0 up  # enables bt on computer
hcitool scan       # gets UUID of devices in pairing mode
hcitool dev        # get BT adapter uuid

bluetoothctl       # starts interactive prompt
scan on            # scans for UUID of device (BT and BLE) in pairing mode
pair uuid          # where "uuid" is what you found with scan
trust uuid
connect uuid       # after pairing, this is how you connect in the future

If you get the error

Creating device failed: org.bluez.Error.AuthenticationRejected: Authentication Rejected

then edit /etc/bin/bluez-simple-agent, changing "KeyboardDisplay" to "DisplayYesNo"

Also try:

bluez-test-device trusted <speaker uuid> yes

If connected but lacking sound, try editing ~/.asoundrc, pasting in:

pcm.btspkr {
   type plug
   slave {
       pcm {
           type bluetooth
           device "AA:BB:CC:DD:EE:FF"
           profile "auto"
       }
   }
   hint {
       show on
       description "BT Speaker"
   }
}
ctl.btspkr {
  type bluetooth
}

pcm.btspkr_softvol
{
   type softvol
   slave.pcm "btspkr"
   control.name "Bluetooth"
   control.card 0
}

# Using bluetooth as default :
pcm.!default {
    type plug
    slave.pcm "btspkr_softvol"
}

hcitool cc <uuid>

I sometimes saw in Ubuntu that it disconnects after a second, maybe because system bluetooth menu is overriding with "off"?

Cannot open shared library /usr/lib/arm-linux-gnueabihf/alsa-lib/libasound_module_pcm_bluetooth.so

apt install bluez-alsa

bt_audio_service_open: connect() failed: Connection refused (111)

1. edit /etc/bluetooth/audio.conf, pasting in:

   [general]
   Enable=Sink,Source,Socket
   Disable=Media
   
   AutoConnect=true
   SCORouting=PCM

2. then:

   service bluetooth restart

First test it works with:

mpg321 -a bluetooth  myfile.mp3

or:

mplayer -ao alsa:device=bluetooth myfile.mp3

Then, list your audio ALSA devices with:

aplay -L

and you can use:

alsamixer

https://bitbucket.org/OscarAcena/pygattlib

https://wiki.archlinux.org/index.php/bluetooth_keyboard

https://github.com/oz123/dude/blob/master/bin/speakersswitcher.sh

http://blog.scphillips.com/2013/01/sound-configuration-on-raspberry-pi-with-alsa/

https://wiki.debian.org/Bluetooth/Alsa

http://www.raspberrypi.org/forums/viewtopic.php?f=63&t=92900

http://samtuke.com/2014/10/manually-pair-bluetooth-devices-on-linux-via-cli-nfc-workaround/

http://www.correderajorge.es/bluetooth-on-raspberry-audio-streaming/

http://www.ioncannon.net/linux/1570/bluetooth-4-0-le-on-raspberry-pi-with-bluez-5-x/

https://gist.github.com/dustywilson/8267078

http://www.correlatedcontent.com/blog/bluetooth-keyboard-on-the-raspberry-pi/