4.1 Overview

Atmel QTouch® Peripheral Touch Controller (PTC) offers built-in hardware for capacitive touch measurement on sensors that function as buttons, sliders, and wheels. The PTC supports both mutual and self-capacitance measurement without the need for any external component. It offers high sensitivity and noise tolerance, as well as self-calibration, and minimizes the sensitivity tuning effort by the user.

The PTC is intended for autonomously performing capacitive touch sensor measurements. The external capacitive touch sensor is typically formed on a PCB, and the sensor electrodes are connected to the analog charge integrator of the PTC using the device I/O pins. The PTC supports mutual capacitance sensors organized as capacitive touch matrices in different X-Y configurations, including Indium Tin Oxide (ITO) sensor grids. In mutual capacitance mode, the PTC requires one pin per X-line (drive line) and one pin per Y-line (sense line). In self-capacitance mode, the PTC requires only one pin with a Y-line driver for each self-capacitance sensor.

This application note uses self-capacitance mode to detect touch on capacitive sensors.

For more details on the PTC module, refer the ATmega328PB datasheet.