STM8T143 datasheet(18/65 Pages) STMICROELECTRONICS

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STM8T143 processing

STM8T143

18/65

DocID18315 Rev 6

5.4

Dynamic calibration (DYCAL)

The STM8T143 DYCAL process is based on a dynamic threshold and reference

management which allows tracking of slow environmental changes even when the sensor is

in touch state. A low threshold is used to detect the proximity of an object, with a higher

threshold for touch detection. DYCAL is performed when a touch condition is detected for

longer than a certain period (tDYCAL). When a release condition occurs, the DYCAL

operation is performed instantaneously. Figure 9 represents the DYCAL operation for the

touch event (DYCAL_T) and for the release event (DYCAL_R).

After the DYCAL_R event, the AET process is frozen for a tAET_HALT delay.

Figure 9. DYCAL general operation

1. tAET_HALT = AET halt period after end of detection.

2. The release threshold (RTh) is a ratio of the touch threshold (TTh). TTh is selected by the “touch detection

threshold” option bits (TTh). The ratio is selected by the “release threshold ratio” option bits.

3. TFTh = Touch freeze threshold. Please refer to Table 16: General capacitive sensing characteristics and

Figure 12: IIR filter formula for the TFTh description.

4. In touch condition, the ECS allows the reference to adapt a slow signal variation change.

STM8T143 Datasheet(PDF) 18 Page - STMicroelectronics