STM8T143 datasheet(14/65 Pages) STMICROELECTRONICS

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STM8T143 processing

STM8T143

14/65

DocID18315 Rev 6

STM8T143 processing

The STM8T143 device is designed to ensure reliable operation whatever the environment

and operating conditions. To achieve this high level of robustness, dedicated processing

have been implemented:

•

Automatic electrode tuning (AET)

•

Signal and reference calibration

•

Detection and release thresholds

•

Dynamic calibration (DYCAL)

•

Environment control system (ECS)

•

Debounce filter

•

Host control input

5.1

Automatic electrode tuning (AET)

AET is a sophisticated technology implemented in the STM8T143 device. It optimizes the

performance of the device in a wide range of applications and environmental conditions.

AET algorithm automatically adjusts the internal CS capacitor and EPCC parameters to

optimize system performance. Please refer to:

•

Table 17: Internal CS value for possible resulting values of this internal sampling

capacitance

•

Table 18: Implemented EPCC values (pF) for possible values of the EPCC

capacitance.

The principle is to select an internal CS capacitor and EPCC to obtain a burst count in a

predefined range of AET target value ± 256 burst counts.

At device startup, CS is selected to reach the nearest signal burst count value to a “gain

target value”. Then, the EPCC hardware subtracts an increasing capacitance value until a

“AET target value” is reached. During normal device operation, the EPCC hardware

subtracts from the electrode capacitance (CX), the compensation capacitance value

determined during the calibration phase.

This automatic system adaptation allows the same burst count number to be reached

regardless of the application electrode and surrounding.

The AET gain can be adjusted by selecting the gain target value through the “Gain target”

option bits.

The AET algorithm is executed whenever the device starts-up and during device operation

when the reference exits burst count range.

During the AET processing (tAET), proximity and touch events cannot be detected (please

refer to Table 6: Data streaming frame). In Data streaming mode, the AET activity is

reported and the internal CS and EPCC values can be monitored (see Section 6.2.3: Data

streaming mode).

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