Using microphone from bluetooth

Question

I have a problem with bluetooth : I can connect to my handsfree device using bluetooth. By default it connects in A2DP mode (good audio quality, but no microphone available). However, when I try to switch back to HSP/HFP (microphone, even if the audio quality is lower) it fails with an error in syslog :

[pulseaudio] module-bluez5-device.c: Refused to switch profile to headset_head_unit: Not connected

And it's very strange since last year I was able to use my bluetooth handsfree device without any problem ! I tried to follow some idea in the web, but no one works for me...

Any idea ?

Thank you !

PS : I'm using pulseaudio version 9.0.

Solution

Finally, after several hours I found a solution : the thing is that the version 5.36 of Bluez is buggy, so you need to install it (to check the installed version, check for example the result of apt-cache policy bluez). The idea is to downgrade (the version 5.35 seems to work), or go to a more recent version (the version 5.40 works). To upgrade, I decided to take the one from experimental repos (I'm running debian unstable). To do so, first add:

deb http://httpredir.debian.org/debian experimental main

in /etc/apt/sources.list. Then run

sudo apt-get update
sudo apt-get -t experimental install bluez

Then reboot and it works ! (or I think that restarting pulseaudio should work:

killall pulseaudio

(It should restart by itself))