94 lines
2.7 KiB
C++
94 lines
2.7 KiB
C++
// -*- tab-width: 4; Mode: C++; c-basic-offset: 4; indent-tabs-mode: nil -*-
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/*
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This program is free software: you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation, either version 3 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program. If not, see <http://www.gnu.org/licenses/>.
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*/
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//
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/// @file LowPassFilter.h
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/// @brief A class to implement a low pass filter without losing precision even for int types
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/// the downside being that it's a little slower as it internally uses a float
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/// and it consumes an extra 4 bytes of memory to hold the constant gain
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#ifndef __LOW_PASS_FILTER_H__
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#define __LOW_PASS_FILTER_H__
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#include <AP_Math/AP_Math.h>
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#include "FilterClass.h"
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// DigitalLPF implements the filter math
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template <class T>
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class DigitalLPF {
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public:
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struct lpf_params {
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float cutoff_freq;
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float sample_freq;
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float alpha;
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};
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DigitalLPF();
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// add a new raw value to the filter, retrieve the filtered result
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T apply(const T &sample, float cutoff_freq, float dt);
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// get latest filtered value from filter (equal to the value returned by latest call to apply method)
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const T &get() const;
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void reset(T value);
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private:
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T _output;
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};
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// LPF base class
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template <class T>
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class LowPassFilter {
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public:
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LowPassFilter();
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LowPassFilter(float cutoff_freq);
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// change parameters
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void set_cutoff_frequency(float cutoff_freq);
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// return the cutoff frequency
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float get_cutoff_freq(void) const;
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T apply(T sample, float dt);
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const T &get() const;
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void reset(T value);
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protected:
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float _cutoff_freq;
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private:
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DigitalLPF<T> _filter;
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};
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// Uncomment this, if you decide to remove the instantiations in the implementation file
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/*
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template <class T>
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LowPassFilter<T>::LowPassFilter() : _cutoff_freq(0.0f) {
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}
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// constructor
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template <class T>
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LowPassFilter<T>::LowPassFilter(float cutoff_freq) : _cutoff_freq(cutoff_freq) {
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}
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*/
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// typedefs for compatibility
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typedef LowPassFilter<int> LowPassFilterInt;
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typedef LowPassFilter<long> LowPassFilterLong;
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typedef LowPassFilter<float> LowPassFilterFloat;
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typedef LowPassFilter<Vector2f> LowPassFilterVector2f;
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typedef LowPassFilter<Vector3f> LowPassFilterVector3f;
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#endif // __LOW_PASS_FILTER_H__
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