Distinguishing sound from 3 sources

Hi all,

My project is car radio; the prototype is fully functioning and supports FM radio and a 3.5mm audio socket.

I've been using a 5 pin audio socket to make the 2 sound sources mechanically switch when desired by the customer. This works, but isn't the nicest solution: the display will be displaying the FM frequency (& radio text & radio station), even if the 3.5mm socket is used (because the Arduino doesn't get a notification of insertion).

However, this is acceptable. But now, I'd like to add the RN-52 (a bluetooth audio module), meaning that I'll have to add an additional audio signal switch (after the 5 pin socket). This isn't difficult, because the Arduino gets a notification from the bluetooth module when bluetooth audio is desired.

Since I'm trying to also remove the rather ugly displaying of FM radio information as long as the phone is physically connected through the 5 pin socket, I can only think of 1 solution, but I'm not sure it will work:

  • Connect "RADIO OUT LEFT" and "AUDIO SOCKET OUT LEFT" to the Arduino and check whether both signals are the same (meaning the mechanical switch in the 5 pin audio socket is closed).

Does this work, or is there a better solution?

Rough wiring scheme (for the left audio channel only):

            {1}                            {2}
               ---> RADIO OUT (no 3.5mm) -> \
3.5MM OUT -> /                                ---> RADIO OUT (no BT. conn.)
BT OUT    ->   ---> BT OUT               -> /

{1} => mechanical 5 pin socket switch (not notifced through Arduino) {2} => Arduino controlled analog switch (CD4066?)