I'm designing a project based on Atmega328P which uses QMatrix to drive 15 capacitive touch buttons. Well, QMatrix sensors requires a couple of resistors and capacitors on sensor pins
Is any issue if some of the ISP pins are wired to capacitors and used as touch?
This schematics shows typical wiring for a single QMatrix sensor, along with recomended component values. X/YA/YB/SMP are simply names QMatrix spec give to pins based on it's role.
The X line and YA line are not directly in eletrical contact on the button, though they form an interdigitated pattern which happens to form a capacitor