AlphaFilter.hpp

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/**
 * First order "alpha" IIR digital filter
 * @author Mathieu Bresciani <brescianimathieu@gmail.com>
 */

#pragma once

template<typename T>
class AlphaFilter final
{
public:
    AlphaFilter() = default;
    ~AlphaFilter() = default;

    void reset(const T &val) { _x = val; }

    void update(const T &input, float tau, float dt)
    {
        const float alpha = dt / tau; 
        update(input, alpha);
    }

    void update(const T &input, float alpha)
    {
        _x = (1.f - alpha) * _x + alpha * input;
    }

    // Typical 0.9/0.1 lowpass filter
    void update(const T &input)
    {
        update(input, 0.1f);
    }

    const T& getState() const { return _x; }

private:
    T _x{}; ///< current state of the filter
};