Datasheet
CY8C20xx6A/H CapSense Design Guide Doc. No. 001-65973 Rev. *A 4
3.5
CSD User Module Low-Level Parameters ........................................................................................................... 21
3.5.1 iDAC Value ............................................................................................................................................. 21
3.5.2
Resolution ............................................................................................................................................... 21
3.5.3 Scanning Speed ..................................................................................................................................... 22
3.5.4
Shield Electrode Out ............................................................................................................................... 22
3.5.5 Precharge Source ................................................................................................................................... 22
3.5.6
Prescaler ................................................................................................................................................ 22
3.5.7 PRS Resolution ...................................................................................................................................... 22
3.5.8
Autocalibration ........................................................................................................................................ 22
3.5.9 iDAC Range ............................................................................................................................................ 23
3.6
CSA_EMC User Module Low-Level Parameters ................................................................................................. 23
3.6.1 Settling Time ........................................................................................................................................... 24
3.6.2
Freq Num ................................................................................................................................................ 24
3.6.3 Spread Spectrum .................................................................................................................................... 24
3.6.4
Raw Data Median Filter .......................................................................................................................... 24
3.6.5 RawData IIR Filter .................................................................................................................................. 24
3.6.6
RawData IIR Filter Coefficient ................................................................................................................ 24
3.6.7 Clock ....................................................................................................................................................... 24
3.7
SmartSense User Module Parameters ................................................................................................................ 25
3.7.1 Shield Electrode Out ............................................................................................................................... 25
3.7.2
Sensor Sensitivity ................................................................................................................................... 25
3.7.3 Multi-Chart for monitoring CapSense user module parameters .............................................................. 25
4.
CapSense Performance Tuning with User Module ................................................................................................... 26
4.1 General Considerations ....................................................................................................................................... 26
4.1.1
Signal, Noise, and SNR .......................................................................................................................... 26
4.1.2 Charge/Discharge Rate .......................................................................................................................... 27
4.1.3
Importance of Baseline Update Threshold Verification ........................................................................... 28
4.2 Tuning the CSA_EMC User Module .................................................................................................................... 29
4.2.1
Clock and Settling Time .......................................................................................................................... 29
4.2.2 C
MOD
....................................................................................................................................................... 31
4.3
Tuning the CSD User Module .............................................................................................................................. 31
4.3.1 High Level API Parameters .................................................................................................................... 35
4.3.2
Set High-Level Parameters ..................................................................................................................... 36
4.4 Using the SmartSense User Module ................................................................................................................... 36
4.4.1
Guidelines for SmartSense ..................................................................................................................... 36
4.4.2 Understanding the Difference ................................................................................................................. 36
4.4.3 SmartSense User Module Parameters ................................................................................................... 37
4.4.4
Scan Time of a CapSense Sensor .......................................................................................................... 37
4.4.5 SmartSense Response Time .................................................................................................................. 38
4.4.6
Firmware Design Guidelines ................................................................................................................... 39
5. Design Considerations ............................................................................................................................................... 41
5.1
Overlay Selection ................................................................................................................................................ 41
5.2 ESD Protection .................................................................................................................................................... 42
5.2.1
Prevent ................................................................................................................................................... 42
5.2.2 Redirect .................................................................................................................................................. 42
5.2.3
Clamp ..................................................................................................................................................... 42