Datasheet

36 Document No. 001-66271 Rev. *B CY8C21x34/B CapSense
®
Design Guide
Figure 4-7. Monitoring the Sensor Signal baSnsSignal
Now open the CapSense wizard, and under the Sensor Settings tab set the finger threshold to the calculated value (it
is 100 for the example as shown in Figure 4-7).
7. The SmartSense sensor tuning process is completed with the previous step. However, there could be scenarios
where the SNR achieved in Step 5 is below 5:1, for example, when using a thicker overlay. In such cases, follow
these recommendations:
 Change the sensitivity level from "Low" to "Medium". If the SNR of 5:1 is still not achieved, change the level
to "High".
 Sometimes, the requirement of 5:1 cannot be achieved due to excess noise observed in the system. Under
these circumstances, software filters should be used. Start with an IIR filter of coefficient 1/2. If this does not
reduce the noise, change the IIR coefficient to 1/4.