Datasheet

CY8C20xx6A/H CapSense Design Guide Doc. No. 001-65973 Rev. *A 19
The SetDefaultFingerThresholds() function is used to set the thresholds to the default value set in the Device Editor.
Possible values are 5 to 255.
3.4.2 Hysteresis
The Hysteresis parameter is used in conjunction with the finger threshold to determine sensor state, as defined in
Equation 4. Hysteresis adds immunity to noisy transitions. This is a debounce feature of a button. The touch state
stays off until the difference counts are a little higher than the finger threshold. The touch state stays on until the
difference counts are a little lower than the noise threshold. This prevents the touch/no touch state machine from
triggering if the difference counts are very noisy and are halfway between noise and finger thresholds.
Possible values are 0 to 255. The Hysteresis parameter setting must be lower than the Finger Threshold parameter
setting.
3.4.3 Debounce
This Debounce parameter adds a counter to the sensor transition from OFF to ON. For the sensor to transition from
OFF to ON, the difference count value must stay above the finger threshold plus hysteresis level for the number of
samples specified.
Possible values are 1 to 255. A setting of 1 provides no debouncing.
3.4.4 Noise Threshold
For individual sensors, the Noise Threshold parameter sets the upper raw count limit for updating the baseline value.
For slider sensors, it sets the lower raw count limit for counting results in the centroid calculation.
Possible values are 3 to 255. The noise threshold value should never be set to higher than Finger Threshold minus
Hysteresis value for proper operation of the user module.
Figure 3-6. Noise and Baseline Update Parameters
3.4.5 Baseline Update Threshold
When the raw count value is above the current baseline and the difference count is below the noise threshold, the
difference between the current baseline and the raw count is accumulated into a "bucket." When the bucket fills
completely, the baseline increments and the bucket is emptied. The Baseline Update Threshold parameter sets the
threshold that the bucket must reach for the baseline to increment.
Possible values are 0 to 255.