The AIRcable SMD module is able to transmit and receive mono audio signals via its analog interfaces. It can do that while maintaining a standard SPP data connection. The BASIC code on the SMD can manage and configure analog interface as well. Over air it uses standard eSCO channels next to the ACL channels for the data connection.
Hardware
Connect a microphone and speaker directly to the AIRcable SMD. The microphone BIAS is provided by the AIRcable SMD module directly and the current configuration matches the TOM-1545 microphone. The defaults are 2.04V BIAS and 0.471mA current. Connect a standard 8 Ohm speaker to the AIRcable SMD module directly. For using it as a headphone, the speaker volume is good enough.
Amplifiers and Line Input
The modules is designed for direct microphone and speaker connection. If you need more volume from the speaker and unbalanced line input, this circuit will do for you.
BASIC code
When receiving a SLAVE connection via the SPP profile for example, the AIRcable SMD will response automatically to a synchronous SCO cannel connect and will start the microphone and speaker hardware automatically.
Using a Linux machine for example, you can use the standard "scotest" tool as part of BlueZ to connect the SCO channel to the microphone and speaker.
As a MASTER on the AIRcable SMD you need to initiate the SCO connection request. The build-in function "A=sco" will do it. Call that function as part of the @MASTER interrupt routine.
