Alpine Phone Micro reusing
The Alpine microphone is located in the ceiling of the Alpine and is amplified directly. This means that it is not possible to connect this microphone to the Android car radio's jack socket. Indeed, this one does not send power to the microphone so the signal will be too weak to be audible. It is therefore necessary to supply the microphone with +5V in order to obtain satisfactory amplification of the signal. By default, the USB socket of the Android station will output 5.5V, if we use this socket we will saturate the microphone amplifier. It is therefore necessary to lower the voltage below 5V.
Tests show that 3.3V is too low for the amplifier while 5V always remains at the saturation limit. A voltage below 4.98V is ideal.
The diagram is therefore as follows:
We can play on the values of the resistors to attenuate the voltage to enter as the resistance on the signal. For my part, these values give me a good result.
(update) the values retained for a card using the Arduino power supply are: 2.2 KOhms and 20K and 100K for the attenuation resistor.
The gray connector with the Black, Red and Yellow wires will be connected to the +5v, GND and Signal-Micro assembly. The other side of the assembly will be connected on the one hand to the Micro input jack of the station and on the other hand to the power supply of the USB port of the Arduino.
A variant is possible to achieve a different attenuation according to the diagram below:
