Filter: add comments and address review comments for harmonic notch
This commit is contained in:
Andy Piper
Andrew Tridgell
parent
6ddaf81439
commit
334ebadd5a
@ -22,47 +22,47 @@
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const AP_Param::GroupInfo HarmonicNotchFilterParams::var_info[] = {
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// @Param: ENABLE
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// @DisplayName: Enable
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// @Description: Enable harmonic notch filter
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// @DisplayName: Harmonic Notch Filter enable
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// @Description: Harmonic Notch Filter enable
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// @Values: 0:Disabled,1:Enabled
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// @User: Advanced
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AP_GROUPINFO_FLAGS("ENABLE", 1, HarmonicNotchFilterParams, _enable, 0, AP_PARAM_FLAG_ENABLE),
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// @Param: FREQ
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// @DisplayName: Base Frequency
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// @Description: Notch base center frequency in Hz
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// @DisplayName: Harmonic Notch Filter base frequency
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// @Description: Harmonic Notch Filter base center frequency in Hz
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// @Range: 10 400
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// @Units: Hz
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// @User: Advanced
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AP_GROUPINFO("FREQ", 2, HarmonicNotchFilterParams, _center_freq_hz, 80),
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// @Param: BW
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// @DisplayName: Bandwidth
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// @Description: Harmonic notch bandwidth in Hz
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// @DisplayName: Harmonic Notch Filter bandwidth
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// @Description: Harmonic Notch Filter bandwidth in Hz
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// @Range: 5 100
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// @Units: Hz
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// @User: Advanced
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AP_GROUPINFO("BW", 3, HarmonicNotchFilterParams, _bandwidth_hz, 20),
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// @Param: ATT
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// @DisplayName: Attenuation
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// @Description: Harmonic notch attenuation in dB
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// @DisplayName: Harmonic Notch Filter attenuation
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// @Description: Harmonic Notch Filter attenuation in dB
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// @Range: 5 30
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// @Units: dB
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// @User: Advanced
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AP_GROUPINFO("ATT", 4, HarmonicNotchFilterParams, _attenuation_dB, 15),
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// @Param: HMNCS
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// @DisplayName: Harmonics
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// @Description: Bitmask of harmonic frequencies to apply notches to. This option takes effect on the next reboot. A maximum of 3 harmonics can be used at any one time
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// @DisplayName: Harmonic Notch Filter harmonics
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// @Description: Bitmask of harmonic frequencies to apply Harmonic Notch Filter to. This option takes effect on the next reboot. A maximum of 3 harmonics can be used at any one time
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// @Bitmask: 0:1st harmonic,1:2nd harmonic,2:3rd harmonic,3:4th hamronic,4:5th harmonic,5:6th harmonic,6:7th harmonic,7:8th harmonic
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// @User: Advanced
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// @RebootRequired: True
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AP_GROUPINFO("HMNCS", 5, HarmonicNotchFilterParams, _harmonics, 3),
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// @Param: REF
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// @DisplayName: Reference value
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// @Description: Reference value associated with the specified frequency to facilitate frequency scaling
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// @DisplayName: Harmonic Notch Filter reference value
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// @Description: Reference value associated with the specified frequency to facilitate frequency scaling of the Harmonic Notch Filter
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// @User: Advanced
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// @Range: 0.1 0.9
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// @RebootRequired: True
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@ -71,9 +71,18 @@ const AP_Param::GroupInfo HarmonicNotchFilterParams::var_info[] = {
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AP_GROUPEND
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};
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/*
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destroy all of the associated notch filters
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*/
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template <class T>
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HarmonicNotchFilter<T>::~HarmonicNotchFilter() {
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delete[] _filters;
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_num_filters = 0;
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}
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/*
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initialise filter
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initialise the associated filters with the provided shaping constraints
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the constraints are used to determine attenuation (A) and quality (Q) factors for the filter
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*/
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template <class T>
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void HarmonicNotchFilter<T>::init(float sample_freq_hz, float center_freq_hz, float bandwidth_hz, float attenuation_dB)
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@ -87,8 +96,10 @@ void HarmonicNotchFilter<T>::init(float sample_freq_hz, float center_freq_hz, fl
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// adjust the center frequency to be in the allowable range
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center_freq_hz = constrain_float(center_freq_hz, bandwidth_hz * 0.52f, sample_freq_hz * 0.48f);
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// calculate attenuation and quality from the shaping constraints
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NotchFilter<T>::calculate_A_and_Q(center_freq_hz, bandwidth_hz, attenuation_dB, _A, _Q);
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// initialize all the configured filters with the same A & Q and multiples of the center frequency
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for (uint8_t i = 0, filt = 0; i < HNF_MAX_HARMONICS && filt < _num_filters; i++) {
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if ((1U<<i) & _harmonics) {
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_filters[filt++].init_with_A_and_Q(sample_freq_hz, center_freq_hz * (i+1), _A, _Q);
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@ -98,10 +109,10 @@ void HarmonicNotchFilter<T>::init(float sample_freq_hz, float center_freq_hz, fl
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}
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/*
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initialise filter
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allocate a collection of, at most HNF_MAX_FILTERS, notch filters to be managed by this harmonic notch filter
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*/
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template <class T>
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void HarmonicNotchFilter<T>::create(uint8_t harmonics)
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void HarmonicNotchFilter<T>::allocate_filters(uint8_t harmonics)
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{
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for (uint8_t i = 0; i < HNF_MAX_HARMONICS && _num_filters < HNF_MAX_FILTERS; i++) {
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if ((1U<<i) & harmonics) {
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@ -114,13 +125,10 @@ void HarmonicNotchFilter<T>::create(uint8_t harmonics)
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_harmonics = harmonics;
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}
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template <class T>
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HarmonicNotchFilter<T>::~HarmonicNotchFilter() {
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if (_num_filters > 0) {
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delete[] _filters;
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}
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}
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/*
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update the underlying filters' center frequency using the current attenuation and quality
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this function is cheaper than init() because A & Q do not need to be recalculated
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*/
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template <class T>
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void HarmonicNotchFilter<T>::update(float center_freq_hz)
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{
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@ -131,6 +139,7 @@ void HarmonicNotchFilter<T>::update(float center_freq_hz)
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// adjust the center frequency to be in the allowable range
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center_freq_hz = constrain_float(center_freq_hz, 1.0f, _sample_freq_hz * 0.48f);
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// update all of the filters using the new center frequency and existing A & Q
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for (uint8_t i = 0, filt = 0; i < HNF_MAX_HARMONICS && filt < _num_filters; i++) {
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if ((1U<<i) & _harmonics) {
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_filters[filt++].init_with_A_and_Q(_sample_freq_hz, center_freq_hz * (i+1), _A, _Q);
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@ -138,6 +147,9 @@ void HarmonicNotchFilter<T>::update(float center_freq_hz)
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}
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}
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/*
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apply a sample to each of the underlying filters in turn and return the output
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*/
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template <class T>
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T HarmonicNotchFilter<T>::apply(const T &sample)
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{
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@ -152,6 +164,9 @@ T HarmonicNotchFilter<T>::apply(const T &sample)
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return output;
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}
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/*
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reset all of the underlying filters
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*/
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template <class T>
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void HarmonicNotchFilter<T>::reset()
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{
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@ -164,9 +179,8 @@ void HarmonicNotchFilter<T>::reset()
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}
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}
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/*
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a notch filter with enable and filter parameters - constructor
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create parameters for the harmonic notch filter and initialise defaults
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*/
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HarmonicNotchFilterParams::HarmonicNotchFilterParams(void)
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{
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@ -174,6 +188,6 @@ HarmonicNotchFilterParams::HarmonicNotchFilterParams(void)
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}
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/*
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instantiate template classes
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instantiate template classes
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*/
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template class HarmonicNotchFilter<Vector3f>;
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@ -16,44 +16,62 @@
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#include <AP_Math/AP_Math.h>
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#include <cmath>
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#include <inttypes.h>
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#include <AP_Param/AP_Param.h>
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#include "NotchFilter.h"
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/*
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a filter that manages a set of notch filters targetted at a fundamental center frequency
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and multiples of that fundamental frequency
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*/
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template <class T>
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class HarmonicNotchFilter {
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public:
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// set parameters
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void create(uint8_t harmonics);
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void init(float sample_freq_hz, float center_freq_hz, float bandwidth_hz, float attenuation_dB);
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T apply(const T &sample);
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void reset();
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void update(float center_freq_hz);
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~HarmonicNotchFilter();
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// allocate a bank of notch filters for this harmonic notch filter
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void allocate_filters(uint8_t harmonics);
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// initialize the underlying filters using the provided filter parameters
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void init(float sample_freq_hz, float center_freq_hz, float bandwidth_hz, float attenuation_dB);
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// update the underlying filters' center frequencies using center_freq_hz as the fundamental
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void update(float center_freq_hz);
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// apply a sample to each of the underlying filters in turn
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T apply(const T &sample);
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// reset each of the underlying filters
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void reset();
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private:
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// underlying bank of notch filters
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NotchFilter<T>* _filters;
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// sample frequency for each filter
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float _sample_freq_hz;
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// attenuation for each filter
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float _A;
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// quality factor of each filter
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float _Q;
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// a bitmask of the harmonics to use
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uint8_t _harmonics;
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// number of allocated filters
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uint8_t _num_filters;
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bool _initialised;
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};
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/*
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notch filter enable and filter parameters
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harmonic notch filter configuration parameters
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*/
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class HarmonicNotchFilterParams : public NotchFilterParams {
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public:
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HarmonicNotchFilterParams(void);
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// set the fundamental center frequency of the harmonic notch
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void set_center_freq_hz(float center_freq) { _center_freq_hz.set(center_freq); }
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// harmonics enabled on the harmonic notch
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uint8_t harmonics(void) const { return _harmonics; }
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// reference value of the harmonic notch
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float reference(void) const { return _reference; }
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static const struct AP_Param::GroupInfo var_info[];
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private:
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// notch harmonics
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AP_Int8 _harmonics;
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// notch reference value
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AP_Float _reference;
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};
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