I have this CSR8645 bluetooth module and I wanted to use TPP223 capacitive buttons for its inputs – vol+, vol-, next, prev, etc., but I am wondering if it will work at all.
The CSR8645 is originally intended to be used with mechanical buttons. Micro buttons like these only make a connection between two of the pins. So their working principle is modulating resistance from ∞Ω to 0Ω. On the other hand the capacitive board outputs 5V on its I/O pin when it's touched. So it modulates voltage from 0V to 5V. I am wondering if this can destroy the I/O port of the CSR8645 chip, which certainly is not expecting a voltage input where just a connection should be made.
By your opinion can I use the TPP223 directly instead of mechanical buttons or do I have to add something like a relay to emulate a mechanical button.
Best Answer
Assuming the Bluetooth module uses standard "push button to ground with an internal pull up" for the button, then all you really need to do is use a NPN transistor (and base resistor) on the output of the cap sense board, to pull the button line down to ground.