Datasheet
CY8C20xx6A/H CapSense Design Guide Doc. No. 001-65973 Rev. *A 20
3.4.6 Negative Noise Threshold
The Negative Noise Threshold parameter acts as a negative difference count threshold. If the raw count is below the
baseline minus the negative noise threshold for the number of samples specified by the Low Baseline Reset
parameter, the baseline is set to the new raw count value.
Possible values are 0 to 255.
3.4.7 Low Baseline Reset
The Low Baseline Reset parameter works together with the Negative Noise Threshold parameter. It counts the
number of abnormally low samples required to reset the baseline. It is used to correct the finger-on-at-startup
condition.
Possible values are 0 to 255.
3.4.8 Sensors Autoreset
This parameter determines whether the baseline is updated at all times, or only when the difference counts are below
the noise threshold.
When Sensors Autoreset is enabled, the baseline is updated constantly. This limits the maximum time duration of the
sensor (typical values are 5 to 10 seconds), but prevents the sensors from permanently turning on when the raw
count accidentally rises without anything touching the sensor. This sudden rise can be caused by a large power
supply voltage fluctuation, a high-energy RF noise source, or a very quick temperature change.
When Sensors Autoreset is disabled, the baseline is updated only when the difference counts are below the noise
Threshold parameter.
Possible values are Enabled and Disabled.
3.4.9 High-Level Parameter Recommendations
The following recommendations are only a starting place for selecting the optimal parameter settings
Finger Threshold: Set to 75 percent of Raw Counts with sensor ON
Noise Threshold: Set to 40 percent of Raw Counts with sensor OFF
Negative Noise Threshold: Set equal to Noise Threshold
Baseline Update Threshold: Set two times Noise Threshold
Hysteresis: Set to 15 percent of Raw Counts with sensor ON
Low Baseline Reset: Set to 10
Sensors Autoreset: Based on design requirements
Debounce: Based on design requirements