I'm wondering, if it would be possible, to place capsense-buttons on a flex PCB. The design guide mentions a max. track length of 50mm for flex cable. Is this still correct, if the top-layer would contain the buttons and the bottom-layer would contain hatched ground and button-signal-tracks? Would this be possible? The complete max. track length would be 5cm on flex-PCB + 2cm flex-cable + 7cm on FR4-PCB.
Or do you have better suggestions for creating a keypad connected to a PCB for controlling the rest of the device?
I am afraid that technical questions like yours can be answered by Cypress only. Create a MyCase (At top of this page: Design Support -> Create a Support Case ...)