Preface
The Microchip T9 Xplained Pro is a capacitive touch extension kit to demonstrate Metal over Cap (MoC). MoC is a technology that enables touch on metal, developed, and patented by Microchip.
The Xplained Pro connector ensures that the T9 XPro can be used with many MCU XPRO boards, as well as Curiosity Nano MCU boards via the Curiosity Nano Touch Adapter (AC80T88A).
Touch on metal, or MoC, utilizes the same elements as regular touch:
- Touch sensor (electrode) on a Printed Circuit Board (PCB)
- Touch Integrated Circuit (IC)
- Touch Firmware (FW)
In contrast to regular touch, the PCB (containing the electrodes) isn't covered with non-conductive material, but with metal, which is separated from the PCB by a spacer layer. For further details, consult the Mechanical Stack-Up section.
The root cause for touch detection is the deflection of the metal surface reducing the distance to the electrode by less than 10 μm. The capacitive touch IC detects the resulting change in capacitance and reports the press to the system.
For more information on MoC, refer to the following two Application Notes:
