STM8T143 datasheet(21/65 Pages) STMICROELECTRONICS

部件名	STM8T143

功能描述	Single-channel capacitive sensor for touch and proximity detection

PDF	65 Pages

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制造商	STMICROELECTRONICS [STMicroelectronics]

网页	http://www.st.com

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21 / 65 page

DocID18315 Rev 6

21/65

STM8T143

STM8T143 processing

5.5

Environment control system (ECS)

5.5.1

ECS principle

The acquired signal value of the capacitive sensing channel increases or decreases

according to environmental conditions such as temperature, power supply, moisture, and

surrounding conductive objects. The STM8T143 includes a built-in digital infinite impulse

response (IIR) filter capable of tracking slow changes in the environment. It is called the

environment control system (ECS). This is a low pass filter with a gain of one. The filter

makes the reference follow slow changes of the signal while fast changes are recognized as

a touch or proximity.

Figure 12. IIR filter formula

Note:

If a touch or proximity is detected, the ECS is disabled for the duration of the reference

freeze timeout. In this case, Yn = Yn_1. As soon as the reference freeze times out or the

detection ends, the filter is set as active again.

STM8T143 数据表(PDF) 21 Page - STMicroelectronics