Usage of Filters to process Capsense data

Question: When do we need the different filters (IIR/Median/FIR)? What is the correct way of sequencing them if I use multiple filters?



CapSense filters are implemented in software (DSP). You can implement as many filters as you want in the code. Following are the recommendations with regards to different types of filters for different types of noise:

1. IIR filter: A single first-order IIR filter is the most popular general purpose CapSense filter. It helps in reducing the random noise in the system.

2. Averaging filter: For AC line or periodic noise, an FIR (moving average) filter by itself is a common choice.

3. Median filter: A 3rd or 5th order median filter is useful when the rawcounts show sudden spikes.

Filter combinations are not common. When selected for an application, the filter combination that has been found most useful is the Median filter followed by IIR.