44.
PTC - Peripheral Touch Controller
44.1. Overview
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.
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.
The number of available pins and the assignment of X- and Y-lines is depending on both package type
and device configuration. Refer to the Configuration Summary and I/O Multiplexing table for details.
Related Links
I/O Multiplexing and Considerations
on page 27
44.2. Features
•
Low-power, high-sensitivity, environmentally robust capacitive touch buttons, sliders, wheels and
proximity sensing
•
Supports wake-up on touch from standby sleep mode
•
Supports mutual capacitance and self-capacitance sensing
–
Mix-and-match mutual-and self-capacitance sensors
•
One pin per electrode – no external components
•
Load compensating charge sensing
–
Parasitic capacitance compensation and adjustable gain for superior sensitivity
•
Zero drift over the temperature and V
DD
range
–
Auto calibration and re-calibration of sensors
•
Single-shot and free-running charge measurement
•
Hardware noise filtering and noise signal de-synchronization for high conducted immunity
•
Selectable channel change delay allows choosing the settling time on a new channel, as required
•
Acquisition-start triggered by command or through auto-triggering feature
•
Low CPU utilization through interrupt on acquisition-complete
•
Supported by the Atmel
®
QTouch
®
Composer development tools. See also Atmel|Start and Atmel
Studio documentation.
Related Links
I/O Multiplexing and Considerations
on page 27
Atmel SAM L22G / L22J / L22N [DATASHEET]
Atmel-42402E-SAM L22G / L22J / L22N_Datasheet_Complete-07/2016
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