AN2927

Hardware implementation

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Hardware implementation

Figure 4 illustrates an implementation example. The capacitive human touch is detected by

measuring the charge/discharge of the RC network composed of R1, R2 and electrode

There is only one “Load I/O” pin for all the electrodes. Resistors R1 and R2 must be placed

as close as possible to the MCU. Resistor R1 (between hundreds Ohms to a few MOhms) is

the main resistor used to adjust the electrode sensitivity to touch. Resistor R2 (10k

Ω) is

optional and is used to reduce noise sensitivity.

Figure 4.

Capacitive touch sensing example implementation

For more information please read Application Note AN2869 Guidelines for designing touch

sensing applications.

MCU

GPIO

“Load I/O”

Electrode #1

R2

R1

GPIO

“Acq I/O”

Electrode #2

Electrode #n

GPIO

GPIO

Finger