Atmel Xplained Pro Evaluation Kit for the ATSAMD21J18A Microcontroller ATSAMD21-XPRO ATSAMD21-XPRO Data Sheet
Product codes
ATSAMD21-XPRO
918
Atmel | SMART SAM D21 [DATASHEET]
Atmel-42181C–SAM-D21_Datasheet–07/2014
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.
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.
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
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Supports mutual capacitance and self-capacitance sensing
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6/10/16 buttons in self-capacitance mode, for 32-/48-/64- pins respectively
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60/120/256 buttons in mutual-capacitance mode, for 32-/48-/64- pins respectively
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Mix-and-match mutual-and self-capacitance sensors
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One pin per electrode – no external components
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Load compensating charge sensing
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Parasitic capacitance compensation and adjustable gain for superior sensitivity
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Zero drift over the temperature and V
DD
range
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Auto calibration and re-calibration of sensors
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Single-shot and free-running charge measurement
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Hardware noise filtering and noise signal de-synchronization for high conducted immunity
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Selectable channel change delay
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Allows choosing the settling time on a new channel, as required
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Acquisition-start triggered by command or interrupt event
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Low CPU utilization through interrupt on acquisition-complete
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5% CPU utilization scanning 10 channels at 50ms scan rate
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Supported by the Atmel
®
QTouch
®
Composer development tool, which comprises QTouch Library project builder and
QTouch analyzer