Cypress CE66058 Manual

Objective
You can achieve the proper sensitivity for sensors in an end system that have a considerable difference in parasitic
capacitance (C ) by tuning the raw counts of each sensor to 60 to 70 percent of the maximum value. This code example
p
describes a method that compensates for differences in sensor raw counts due to variations in C
with different bleed resistors.
Requirements
Project Name: Example_Dynamic_Bleed_Resistor
Programming Language: C
Associated Part Families:
Designer™ 5.4 Build 2946
Software Version: PSoC
Related Hardware: CY3280-24x94
Overview
®
In some CapSense designs, the dimensions of the sensing elements vary widely, which in turn causes variations in the C
the different sensors. For example, the C
the CapSense pin of the device. See
To implement the CapSense Sigma Delta (CSD) functionality in a CY8C24x94 device, connect an external modulation
capacitor (Cmod) and a bleed resistor (Rb) to the device, as shown in
architecture in the CY8C24x94 CapSense controller, refer to the
tuning the CSD User Module in the CY8C24x94 CapSense controller, refer to
www.cypress.com
CY8C24x94
UCC, CY3280-SLM,
may vary because of a difference in size or the length of the trace from the button to
p
Figure 1.
Figure 1. CapSense Design with Different Sensor C
Figure 2. CapSense Design Using the CY8C24x94 Device
Rb1
Cmod
Document No. 001-66058 Rev.*E
CE66058 - Dynamically Switch CSD Bleed
CY3240-I2USB Bridge/MiniProg1/MiniProg3
Figure
CY8C21x34/B CapSense Design
Appendix: CSD
Vdd
CY8C24x94
Resistor
by scanning the sensors
p
p
2. For more information about the CSD
Guide. To learn more about
Calibration.
CS0
CS1
CSn
of
p
1