We're looking forward to upgrade our system keypads from 4x4 matrix membrane to Capacitive Touch Membrane Switch looking for durability and other benefits.
We tried a TTP229 based module to input each individual key and read the information through the I2C interface on the module.
While we can interface the module and read Ko..K15 when finger touching the pins, but when we connect the keypad below we have no readings (Keypad has an Autotex F200 Graphic Overlay ).
connecting only one track of the keypad connector to the TTP229 module (K0) we found that it continuously read the key even when not touched. We change capacitors on the module to change sensibility and go from continous reading to no sensing.
Common trace on the keypad is not used with this module, and perhaps that's the missing part to make it work. Perhaps we're using the wrong module and need to change the circuit.
I post my case in the belief that many designers are facing the same problem migrating from matrix to touch keypads.
Any feedback will be greatly appreciated.