Butterworth Filter

The ButterworthFilter class provides an implementation of a Digital Butterworth Filter, implemented as biquad sections (second order sections).

API Reference

Header File

• components/filters/include/butterworth_filter.hpp

Classes

template<size_t ORDER, class Impl = BiquadFilterDf1>
class ButterworthFilter : public espp::SosFilter<(ORDER + 1) / 2, BiquadFilterDf1>

Digital butterworth filter, implemented as biquad sections (Second Order Sections).

Note

See https://en.wikipedia.org/wiki/Butterworth_filter for more information.

Template Parameters:

• ORDER – The order of the filter.

• Impl – Which Biquad implementation form to use.

Public Functions

inline explicit ButterworthFilter(const Config &config)

Construct the butterworth filter for the given config.

Parameters:

config – The configuration struct for the Butterworth Filter

inline float update(float input)

Filter the signal sampled by input, updating internal state, and returning the filtered output.

Parameters:

input – New sample of the input data.

Returns:

Filtered output based on input and history.

inline float operator()(float input)

Filter the signal sampled by input, updating internal state, and returning the filtered output.

Parameters:

input – New sample of the input data.

Returns:

Filtered output based on input and history.

struct Config

Butterworth configuration.

Public Members

float normalized_cutoff_frequency

Filter cutoff frequency in the range [0.0, 0.5] (normalizd to sample frequency, = 2 * f_cutoff / f_sample).