I'm building a project which needs a 12 keys keypad, like the telephone one.
As ESP32 has 9 usable touch pins (GPIO 0 cause boot issues) one possible solution is make a matrix keypad, and the best way I found to do this is using mutual capacitances, based in the section 4.2 of this document
but as I understand ESP32 implementation is quite different (please correct me if I'm wrong), it charge and discharge the pads periodically, using a self-capacitance technique, and when human body disturb this capacitance it generate a variation like the picture bellow:
The way that I found to implement using seft-capacitance is putting the pads of rows and columns very near in the top plane, making a touch trigger a row and a column at same time, like this picture: https://image.prntscr.com/image/AVtjj9A ... P8IiDQ.png
The only problem is the very weak sensibility, like 5% of variation when a 2mm acrylic cover is placed over it, and the less area causes less sensitivity
There is some better way to design a layout of matrix keypad using ESP32 self-capacitance or how hard is make it works using mutual capacitance?
Obs: most images was suppressed due too much visual pollution