6. Created a new file by sudo vi /etc/asound.conf and added the following as its sole content (if you know the MAC address of your Bluetooth device, substitute it already now; otherwise you can change it also later in step 9):

This was a very important reason why "pa rescan " had failed for me previously: I had defined the devices in the .asoundrc of the user pi, but freeswitch was running with the user "freeswitch" who has no login shell and hence cannot have any .asoundrc --> device configuration had to go to a user-independent level.

The suggested content for this file tried to get a better output quality by making use of the "a2dp" profile whereas for the mic you have to use the "sco" profile. However, in this combination pa is eventually working in a pretty unstable way. Therefore, we can simplify the content the following way:

pcm.btAudioIO {
        type plug
        slave.pcm {
                type bluealsa
                service "org.bluealsa"
                device "00:11:09:94:14:3D"
                profile "sco"
                delay 10000
        }
        hint {
                show on
                description "Bluetooth Audio Input/Output Dvice"
        }
}

ctl.btAudioIO {
        type bluealsa
        service "org.bluealsa"
        battery yes
}

10. Test your device with the following two commands (five seconds recording):
    arecord -D btAudioIO -d 5 test.wav
    aplay -D btAudioIO test.wav
    

You may also perform a loop test:

arecord -D btAudioIO | aplay -D btAudioIO

After a reboot, after which also FreeSwitch and my application start, everything was working for me just fine :-)

I forgot to say that you can test the working of the setup in fs_cli the following way:

1. "pa devlist" should generate an output like "0;btAudioIO(ALSA);128;128;r,i,o"
2. Like the test at the level of shell, the actual test can be the loop test: "pa looptest"

KR,

-- Saied