Datasheet

CY8C20xx6A/H CapSense Design Guide Doc. No. 001-65973 Rev. *A 17
3.3 CapSense User Module Global Arrays
Before studying CapSense User Module parameters, you need to know certain global arrays used by the CapSense
system to ensure proper detection and operation in spite of environmental changes. These arrays should not be
altered manually, but may be inspected for debugging purposes.
Figure 3-4. Global Parameters
3.3.1 Raw Count
The CapSense controller hardware measures the capacitance and provides the result in a digital form called Raw
Count. The value of Raw Count increases as sensor capacitance increases.
Raw count values are stored in an integer array named UMname_waSnsResult[] where UMname is CSD,
SmartSense, or CSA_EMC.
3.3.2 Baseline
The raw count values of a sensor vary gradually due to changes in the environment such as temperature and
humidity. These gradual variations are compensated for with the baseline values. The baseline keeps track of gradual
changes in raw count using a software algorithm. It is a low-pass filter that is less sensitive to sudden changes in the
raw count. The baseline values provide the reference level for computing the difference counts.
Baseline values are stored in an integer array named UMname_waSnsBaseline[] where UMname is CSD,
SmartSense, or CSA_EMC.