sudo vi /lib/systemd/system/bthelper@.service

sudo apt-get update  && 
                sudo apt-get install -y bluealsa

              

            
sudo vi
                /lib/systemd/system/bluealsa.service
ExecStart=/usr/bin/bluealsa
Environment=LIBASOUND_THREAD_SAFE=0

               ExecStart=/usr/bin/bluealsa -p hfp-hf -p hsp-hs -p hfp-ag
            -p hsp-ag -p a2dp-source -p a2dp-sink

          

        
sudo vi
                  /lib/systemd/system/bluetooth.service

          --> Added --noplugin=sap
 to the
              end of the following line

                 ExecStart=/usr/lib/bluetooth/bluetoothd

                

              
sudo vi
                          /lib/systemd/system/bthelper@.service

                --> Added ExecStartPre=/bin/sleep
                      2 in
                      a new line after

                         Type=simple

                        

                      
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):

                        pcm.btAudioIO {

                                  type asym

                                  playback.pcm {

                                          type plug

                                          slave.pcm {

                                                  type bluealsa

                                                  service "org.bluealsa"

                                                  device
                          "00:11:09:94:14:3D"

                                                  profile "a2dp"

                                                  delay 10000

                                          }

                                  }

                                  capture.pcm {

                                          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"

                                  }

                          }

                        

                        
sudo adduser freeswitch audio

              sudo adduser 
freeswitch bluetooth

              sudo reboot

            
After reboot, run sudo
                        bluetoothctl and then find, pair, connect
                          and trust your Bluetooth device with the
                          following control commands of this program:

                        agent on

                            scan on
        <-- find the MAC
                                    address of your device in the scan
                                    outputs

                                              pair
                            50:11:2D:06:ED:2F

                          
scan off

                                                          
--> from now on, your device
                                                          should
                                                          automatically
                                                          reconnect to
                                                          the pi each
                                                          time after the
                                                          pi is
                                                          rebooted; if,
                                                          however, this
                                                          is not the
                                                          case, you will
                                                          have to redo
                                                          this step
                                                          after each
                                                          reboot.

                                                          

                      
In this example, the device
                          that I have paired and trusted has a different
                          MAC address as the one in /etc/asound.conf;
                          therefore we must edit the file and set the
                          right MAC address. If you already had the
                          right MAC address, you may go to the next step
                          without reboot; but, if you had to change the
                          file /etc/asound.conf, then you will have to
                          reboot before going to the next step.

                          

                        
Test your device with the
                          following two commands (five seconds
                          recording):

                        arecord -D btAudioIO -d 5 test.wav

                            aplay 
-D btAudioIO
                                                test.wav

                                              

                      
Assuming that the above test is
                          successful, you now 

                          - edit <FreeSwitch-Config-Home>/autoload_configs/modules.conf.xml
                          and un-comment the loading of mod_portaudio

                          - edit 
<FreeSwitch-Config-Home>/autoload_configs/portaudio.conf.xml
                                            and substitute the whole
                                            content with the following
                                            new content:

                                          
<configuration
                                          name="portaudio.conf"
                                          description="Soundcard
                                          Endpoint">

                                            <settings>

                                              <param name="indev"
                                          value="btAudioIO"/>

                                              <param name="outdev"
                                          value="btAudioIO"/>

                                              <param name="ringdev"
                                          value="btAudioIO"/>

                                              <param name="hold-file"
                                          value="$${hold_music}"/>

                                              <param name="dialplan"
                                          value="XML"/>

                                              <param name="cid-name"
value="$${outbound_caller_name}"/>

                                              <param name="cid-num"
                                          value="$${outbound_caller_id}"/>

                                              <param
                                          name="sample-rate"
                                          value="48000"/>

                                              <param name="codec-ms"
                                          value="20"/>

                                            </settings>

                                          </configuration>c

                                          

                                      

In my case, I
                                            didn't need to do anything
                                            for dial plans because in my
                                            system both the in- and
                                            outbound calls are first
                                            handled by my python
                                            scripts; in particular, the
                                            BT handsfree device 
is never
                                            supposed to make calls but
                                            is called for making
                                            announcements or invited to
                                            a running call 
as the
                                                third leg. So far, I was
                                                using an IP telephone
                                                with auto-answering
                                                capability as extension
                                                000 of my FreeSwitch for
                                                this purpose. To
                                                substitute that phone
                                                with the BT handsfree
                                                device, I just needed to
                                                update my related python
                                                script with the
                                                following command:

                                              
sudo sed -i
                                              's#user/000@[0-9.]+#portaudio/auto_answer#g'
                                              dial.py