STM8T143 STMicroelectronics, STM8T143 Datasheet - Page 17

• Manufacturer Part Number: STM8T143
• Description: Single-channel capacitive sensor for touch and proximity detection
• Manufacturer: STMicroelectronics

STM8T143
5.3
Detection and release thresholds
During the detection operation, after calibration is over, the STM8T143 switches between
three operating states: no detection, proximity detection, and touch detection. The switch
between these states is driven by the difference between the signal and the reference.
The system goes from no detection to proximity detection state when the (reference - signal)
is higher than the proximity threshold (PTh). In this state, the ECS is halted and the
reference is frozen.
The system goes from no detection or proximity detection state to touch detection state
when the (reference - signal) is higher than the touch threshold (TTh). When this happens,
the reference value is changed to reflect the touch state after the delay t
process is called dynamic calibration (DYCAL).
The system goes from the touch detection to no detection state when the (signal -
reference) goes above the release threshold (RTh). At this point, another DYCAL occurs for
the reference to represent the untouched state again.
For higher flexibility, several proximity and touch detection thresholds are available and
independently selectable through option byte: one PTh and one TTh.
●
●
The release threshold is a ratio of the the touch threshold noted (TTh). TTh is selected by
the “touch detection threshold” option bits. The ratio is selected by the “release threshold
ratio” option bits.
A time filtering, similar to the debouncing of the mechanical switches, is applied to avoid
noise induced detections.
Please refer to
Figure 8
"Δ (signal)". The Δ (signal) is the absolute value of the reference minus the signal.
The touch thresholds allow the touch sensitivity to be adapted to the panel thickness
and the electrode sensitivity.
The proximity thresholds allow the STM8T143 device to adapt to various surroundings
and to tune the detection distance.
simplifies the proximity and touch detection event according to the signal variation
Section 5.6: Debounce filter
Doc ID 18315 Rev 3
for operation details.
STM8T143 processing
DYCAL_T
. This
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