44.5.1.2. Self-capacitance Sensor Arrangement
The self-capacitance sensor is connected to a single pin on the Peripheral Touch Controller through the Y
electrode for receiving the signal. The sense electrode capacitance is measured by the Peripheral Touch
Controller.
Figure 44-4. Self-capacitance Sensor Arrangement
MCU
PTC
Module
Y
0
Y
1
Y
m
C
y0
C
y1
C
ym
Sensor Capacitance C
y
For more information about designing the touch sensor, refer to Buttons, Sliders and Wheels Touch
Sensor Design Guide on
44.5.2. Clocks
The PTC is clocked by the GCLK_PTC clock.. The PTC operates from an asynchronous clock source and
the operation is independent of the main system clock and its derivative clocks, such as the peripheral
bus clock (CLK_APB). A number of clock sources can be selected as the source for the asynchronous
GCLK_PTC. The clock source is selected by configuring the Generic Clock Selection ID in the Generic
Clock Control register. For more information about selecting the clock sources, refer to
GCLK - Generic
Clock Controller
.
The selected clock must be enabled in the Power Manager, before it can be used by the PTC. By default
these clocks are disabled. The frequency range of GCLK_PTC is 400kHz to 4MHz.
Related Links
GCLK - Generic Clock Controller
on page 121
44.6. Functional Description
In order to access the PTC, the user must use the QTouch Composer tool to configure and link the
QTouch Library firmware with the application code. QTouch Library can be used to implement buttons,
sliders, wheels and proximity sensor in a variety of combinations on a single interface.
Atmel SAM L22G / L22J / L22N [DATASHEET]
Atmel-42402E-SAM L22G / L22J / L22N_Datasheet_Complete-07/2016
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