STM8T143AU62TTR Datasheet, PDF (14/65 Pages) STMicroelectronics – Single-channel capacitive sensor for touch and proximity detection

STM8T143 processing
5
STM8T143 processing
STM8T143
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 C_S 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 C_S capacitor and EPCC to obtain a burst count in a
predefined range of AET target value ± 256 burst counts.
At device startup, C_S 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 (C_X), 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 (t_AET), 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 C_S and EPCC values can be monitored (see Section 6.2.3: Data
streaming mode).
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