BT audio on devices without BT but with mini jack out and AUX ports.

I was strugling a lot with Sound and Bluetooth on my ThinkPad x240 laptop, which is running FreeBSD 12.1. This laptop has some issue with the speaker, volume is very low, I hardly hear anything, but the mini jack works ok. There were few ways to solve it.

  • 1 - Repair the built in speaker, but it was the last thing I wanted to do.
  • 2 - Use headphones or external speakers connected with cables to mini jack headphones port, but again cables.
  • 3 - Use Bluetooth speaker or headphones.

I thought BT audio is a nice idea and I wanted to try it out. It turned out that Bluetooth support at FreeBSD is quite poor, and at OpenBSD they remove the Bluetooth stack completely. I bought CSR 4.0 Bluetooth USB dongle and Bluetooth audio receiver BTR-302 (v3.0 + EDR ). I managed to create a BT audio connection. bt-audio-BTR-302.jpg

sudo service bluetooth start ubt1

# search for BT devices
sudo hccontrol -n ubt1hci inquiry

#it found a device 30:21:65:55:11:29

sudo hccontrol -n $ubt1hci create_connection 30:21:65:55:11:29

# Disable kernel's /dev/dsp
sudo sysctl hw.snd.basename_clone=0

sudo virtual_oss -C 2 -c 2 -r 48000 -b 16 -s 768 -R /dev/null -P /dev/bluetooth/30:21:65:55:11:29 -d dsp

After that I  was able to play music by audacious and videos by mplayer:

mplayer -ao oss:/dev/dsp movie-file-mp4

It is important to stop BT stack

sudo service bluetooth stop ubt1

It worked with the BT dongle and this small BT receiver, but the receiver has a very small battery which is not enought for watching or listening for 2 hours. I did not managed to connect to more modern BT headphones or spekers like JBL Flik4 or Fioo uBTR.

  • 4 - Next I decided to look further for other possible solutions like BT adapter which I can power using USB charger. I found BT adapters that can work as transmitter and receiver. I bought two of them and again I failed. These devices presents themselve as KN320. First time they connected to each other easily without any problem but as long as I was testing it I found out that this is very unstable behaviour. Transmitter adapter can be connect to any source device that has audio out by mini jack. The receiver can be connect with external speakers or headphones also by mini jack. These BT adapters do not have any batteries and thy need to be powered by USB type A port. bt-audio-KN-320.jpg

  • 5 - I bought also one cheap BT receiver (Bluetooth V2,1 + EDR, V1.2 A2DP ) that is powered from USB. It is named BT-163. Right now it is the best option.

bt-audio-BT-163.jpg

sudo service bluetooth start ubt1

# search for BT devices
sudo hccontrol -n ubt1hci inquiry

#it found a device a3:94:5b:e0:27:db 

sudo hccontrol -n $ubt1hci create_connection a3:94:5b:e0:27:db 

# Disable kernel's /dev/dsp
sudo sysctl hw.snd.basename_clone=0

sudo virtual_oss -C 2 -c 2 -r 48000 -b 16 -s 768 -R /dev/null -P /dev/bluetooth/a3:94:5b:e0:27:db -d dsp

After that I  was able to play music by audacious and videos by mplayer:

mplayer -ao oss:/dev/dsp movie-file-mp4

It is important to stop BT stack

sudo service bluetooth stop ubt1