PSoC 4 CapSense Sensor Auto-Reset – KBA222882

Version: **

 

Question:

How does PSoC® 4 CapSense® sensor auto-reset work?

 

Answer:

When a filtered raw count is calculated from noise filters, there are three cases for baseline update:

  • Case 1: The filtered raw count is lower than the negative noise threshold. In this case, the device executes the low baseline reset process. The baseline is not updated.
  • Case 2: The filtered raw count is in within the positive and negative noise threshold range. In this case, the device executes the baseline update process. The process is shown in Fig-1.
  • Case 3: The filtered raw count is higher than the positive noise threshold. In this case, if ‘Sensor auto reset’ is disabled, the baseline is not updated; if sensor auto-reset is enabled, the device executes the baseline update process. The process is shown in Fig-1.

 

Untitled.pngFig-1

Enabling sensor auto-reset limits the maximum duration for which the sensor stays ON (typically 5 to 10 seconds). This setting prevents the sensors from permanently turning ON when the raw count accidentally rises because of a large power supply voltage fluctuation, or a sudden change in noise conditions. Use this setting to avoid latch-up of sensors in high-noise conditions. In some cases, if you want to stretch the maximum time duration for sensor staying ON with sensor auto-reset enabled, modify the size of Baseline_Update_Buffer (default size is 8-bit). Contact Cypress sales or technical support for more information.

Reference:

PSoC® 4 and PSoC Analog Coprocessor CapSense® Design Guide

PSoC 4 Capacitive Sensing (CapSense®) Datasheet