Is it possible to DIY your own capacitative touchpad on a PCB? The last page of this mentions it:
"The sensor channels are grouped as rows and columns. Row and column cells are arranged in an interleaving pattern. The size of the cells should be designed so that when a finger touch is detected, a few cells are covered by the finger. Proper overlapping of cells is important to obtain good finger resolution."
So it seems like you have to have two layers, one having metal vertically and the other horizontally. I'd like to do this as cheaply as possible so I'd like to try to implement this on a standard 2-layer piece of FR-4, probably 0.8mm thick (half the standard thickness).
Or, the matrix keypad method mentioned above seems like it'd work, if the "keys" were placed together to have little gap. My overall goal is to have smooth input instead of discrete keys.