Filter Cascade Library

This library provides an implementation for digital filter cascades, supporting high-pass, low-pass, band-pass, and band-stop filters. It allows initializing, updating, and managing filter cascades for signal processing applications.

Features

• Filter Types: High-pass, Low-pass, Band-pass, and Band-stop.
• Filter Order: Configurable by the user, with a default maximum order of 6.
• Reset and Update: Easily reset and update filter states for real-time processing.
• Configurable Parameters: Set filter type, order, center frequency, bandwidth, and sampling frequency.

File Structure

• CascadeFilters.h: Contains the declarations of the filter cascade structures and functions.
• CascadeFilters.c: Contains the implementation of the filter cascade functions.

Installation

Simply include the CascadeFilters.h and CascadeFilters.c files in your project and ensure they are part of your build system.

Usage

Initialization

To initialize a filter cascade, use filterCascadeInitialise:

FilterCascade cascade;
filterCascadeInitialise(
    &cascade,
    FILTER_TYPE_BANDPASS,  // Filter type
    3,                    // Number of filters
    1000.0,               // Center frequency (Hz)
    200.0,                // Bandwidth (Hz)
    44100.0               // Sampling frequency (Hz)
);

Updating the Filter

To process an input signal through the filter cascade:

double output = filterCascadeUpdate(&cascade, input);

Resetting the Filter

To reset the filter's internal states:

filterCascadeReset(&cascade);

API Reference

Functions

void filterCascadeInitialise(FilterCascade* cascade, FilterType type, int numberOfFilters, double centerFrequency, double bandwidth, double sampleFrequency)

Initializes a filter cascade.

• Parameters:
  • cascade: Pointer to a FilterCascade structure.
  • type: Type of the filter (e.g., FILTER_TYPE_HIGHPASS).
  • numberOfFilters: Number of cascaded filters.
  • centerFrequency: Center frequency in Hz.
  • bandwidth: Bandwidth in Hz.
  • sampleFrequency: Sampling frequency in Hz.

double filterCascadeUpdate(FilterCascade* cascade, double input)

Processes an input signal through the filter cascade and returns the filtered output.

• Parameters:
  • cascade: Pointer to the initialized FilterCascade.
  • input: Input signal value.

void filterCascadeReset(FilterCascade* cascade)

Resets the filter's internal states.

• Parameters:
  • cascade: Pointer to the FilterCascade.

Constants

• FILTER_ORDER_MAX: Maximum supported filter order (6).