49.5.1 I/O Lines

The I/0 lines used for analog X-lines and Y-lines must be connected to external capacitive touch sensor electrodes. External components are not required for normal operation. However, to improve the EMC performance, a series resistor of 1kΩ or more can be used on X-lines and Y-lines.

Mutual-Capacitance Sensor Arrangement

A mutual-capacitance sensor is formed between two I/0 lines - an X electrode for transmitting and Y electrode for sensing. The mutual capacitance between the X and Y electrode is measured by the Peripheral Touch Controller.

Figure 49-3. Mutual Capacitance Sensor Arrangement

Self-Capacitance Sensor Arrangement

A self-capacitance sensor is connected to a single pin on the Peripheral Touch Controller through the Y electrode for sensing the signal. The sense electrode capacitance is measured by the Peripheral Touch Controller.

Figure 49-4. Self-Capacitance Sensor Arrangement

For more information about designing the touch sensor, refer to Buttons, Sliders and Wheels Touch Sensor Design Guide.