The ATmega328PB is the first 8-bit Atmel AVR device to feature the successful Atmel QTouch Peripheral Touch Controller (PTC). The Peripheral Touch Controller (PTC) acquires signals in order to detect touch on capacitive sensors. The external capacitive touch sensor is typically formed on a PCB, and the sensor electrodes are connected to the analog front end of the PTC through the I/O pins in the device. The PTC supports both self and mutual capacitance sensors.
The PTC supports 24 buttons in self-capacitance mode and up to 144 buttons in mutual-capacitance mode. It is possible to mix and match mutual-and self-capacitance sensors. Only one pin is required per electrode—no external components are required providing considerable savings on the BOM cost compared to competing solutions.
In mutual-capacitance mode, sensing is performed using capacitive touch matrices in various X-Y configurations. Whereas in self-capacitance mode, the PTC requires only one pin (Y-line) for each touch sensor.
Refer to the chapter I/O Multiplexing in the ATmega328PB device datasheet for details on the pin mapping for this peripheral. A signal can be mapped on several pins.