STM8T143 datasheet(15/65 Pages) STMICROELECTRONICS

Part #	STM8T143

Description	Single-channel capacitive sensor for touch and proximity detection

PDF	65 Pages

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Manufacturer	STMICROELECTRONICS [STMicroelectronics]

Direct Link	http://www.st.com

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15 / 65 page

DocID18315 Rev 6

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STM8T143

STM8T143 processing

Figure 7. Automatic electrode tuning (AET)

1. For the AET and gain target values, please refer to Table 16: General capacitive sensing characteristics.

5.2

Signal calculation and reference calibration

The capacitance change, induced by the presence of a finger or a hand in the device

detection area, is sensed by the variation in the number of charge transfer pulses

composing the burst. The number of charge transfer pulses is called “burst count”. The burst

count is filtered against the noise and compared to a “reference” to determine if there is a

touch/proximity detection. Please refer to Section 5.5: Environment control system (ECS)

for more details about the filtering process.

The reference is calculated at device startup during the calibration phase by averaging the

first 44 measurements before normal device operation.

Then, the environment control system takes care of the reference slow evolution over time.

STM8T143 Datasheet(PDF) 15 Page - STMicroelectronics