Data Sheet

Atmel | SMART SAM D21 [DATASHEET]

Atmel-42181G–SAM-D21_Datasheet–09/2015

35. PTC - Peripheral Touch Controller

35.1 Overview

The purpose of PTC is to acquire signals 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.

In mutual-capacitance mode, sensing is done using capacitive touch matrices in various X-Y configurations, including

indium tin oxide (ITO) sensor grids. The PTC requires one pin per X-line and one pin per Y-line.

In self-capacitance mode, the PTC requires only one pin (Y-line) for each touch sensor.

35.2 Features

z Low-power, high-sensitivity, environmentally robust capacitive touch buttons, sliders, wheels and proximity sensing

z Supports mutual capacitance and self-capacitance sensing

z 6/10/16 buttons in self-capacitance mode, for 32-/48-/64- pins respectively

z 60/120/256 buttons in mutual-capacitance mode, for 32-/48-/64- pins respectively

z Mix-and-match mutual-and self-capacitance sensors

z One pin per electrode – no external components

z Load compensating charge sensing

z Parasitic capacitance compensation and adjustable gain for superior sensitivity

z Zero drift over the temperature and V

range

z Auto calibration and re-calibration of sensors

z Single-shot and free-running charge measurement

z Hardware noise filtering and noise signal de-synchronization for high conducted immunity

z Selectable channel change delay

z Allows choosing the settling time on a new channel, as required

z Acquisition-start triggered by command or interrupt event

z Low CPU utilization through interrupt on acquisition-complete

z 5% CPU utilization scanning 10 channels at 50ms scan rate

z Supported by the Atmel

QTouch

Composer development tool, which comprises QTouch Library project builder and

QTouch analyzer