DocID024847 Rev 2

17/26

AN4316

Tuning of the thresholds

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4.3

Debounce settings

In order to improve the robustness of the application, the STMTouch driver provides the

debounce feature. To validate a touch detection, the delta must have exceeded the

threshold during a certain number of consecutive samples as shown in Figure 8. This is to

avoid a false-detection due to a noise peak.

Figure 8. Debouncing example

Due to the use of a down-counter, the DEBOUNCE preprocessor constant must be set to n-

1 while n consecutive sample must be measured below the detection threshold before

triggering a detection.

#define TSLPRM_DEBOUNCE_DETECT (2) //3 consecutive samples needed to enter

in Detection.

The debounce feature is configurable for each state transition:

•

TSLPRM_DEBOUNCE_PROX: while switching from release state to proximity state

•

TSLPRM_DEBOUNCE_DETECT: while switching from release state or proximity to

touch detection state

•

TSLPRM_DEBOUNCE_RELEASE: while switching from touch or proximity state to

release state

•

TSLPRM_DEBOUNCE_CALIB: while switching from release state to calibration state

(compute again the reference)

•

TSLPRM_DEBOUNCE_ERROR: while switching from any state to error state