Hi,
Before you can use a digital filter, you need digital data.
Where do you get it from?
Do you use an ADC? Are there analog filters used, or oversampling...maybe undersampling...
What data rate, what bit width?
And what after the filter?
Do you know about biquads? If not, then read about them.
*******
Digital filters are everywhere. Sometimes you don't recognize them as filters.
Audio, delay, echo, sound.....
Oversampling in an UART. Debouncing of digital inputs. Averaging of any values. PID regulation loops.
Changing brightness, contrast, or anything other in a picture
Once you know how they work you will use them many times..
Klaus