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- /*
- This program is free software: you can redistribute it and/or modify
- it under the terms of the GNU General Public License as published by
- the Free Software Foundation, either version 3 of the License, or
- (at your option) any later version.
- This program is distributed in the hope that it will be useful,
- but WITHOUT ANY WARRANTY; without even the implied warranty of
- MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
- GNU General Public License for more details.
- You should have received a copy of the GNU General Public License
- along with this program. If not, see <http://www.gnu.org/licenses/>.
- */
- //
- /// @file ModeFilter.h
- /// @brief A class to apply a mode filter which is basically picking the median value from the last x samples
- /// the filter size (i.e buffer size) should always be an odd number
- #pragma once
- #include <inttypes.h>
- #include "FilterClass.h"
- #include "FilterWithBuffer.h"
- template <class T, uint8_t FILTER_SIZE>
- class ModeFilter : public FilterWithBuffer<T,FILTER_SIZE>
- {
- public:
- ModeFilter(uint8_t return_element);
- // apply - Add a new raw value to the filter, retrieve the filtered result
- virtual T apply(T sample) override;
- // get - get latest filtered value from filter (equal to the value returned by latest call to apply method)
- virtual T get() const {
- return _output;
- }
- private:
- // private methods
- uint8_t _return_element;
- T _output;
- void isort(T sample, bool drop_high_sample);
- bool drop_high_sample; // switch to determine whether to drop the highest or lowest sample when new value arrives
- };
- // Typedef for convenience
- typedef ModeFilter<int8_t,3> ModeFilterInt8_Size3;
- typedef ModeFilter<int8_t,4> ModeFilterInt8_Size4;
- typedef ModeFilter<int8_t,5> ModeFilterInt8_Size5;
- typedef ModeFilter<int8_t,6> ModeFilterInt8_Size6;
- typedef ModeFilter<int8_t,7> ModeFilterInt8_Size7;
- typedef ModeFilter<uint8_t,3> ModeFilterUInt8_Size3;
- typedef ModeFilter<uint8_t,4> ModeFilterUInt8_Size4;
- typedef ModeFilter<uint8_t,5> ModeFilterUInt8_Size5;
- typedef ModeFilter<uint8_t,6> ModeFilterUInt8_Size6;
- typedef ModeFilter<uint8_t,7> ModeFilterUInt8_Size7;
- typedef ModeFilter<int16_t,3> ModeFilterInt16_Size3;
- typedef ModeFilter<int16_t,4> ModeFilterInt16_Size4;
- typedef ModeFilter<int16_t,5> ModeFilterInt16_Size5;
- typedef ModeFilter<int16_t,6> ModeFilterInt16_Size6;
- typedef ModeFilter<int16_t,7> ModeFilterInt16_Size7;
- typedef ModeFilter<uint16_t,3> ModeFilterUInt16_Size3;
- typedef ModeFilter<uint16_t,4> ModeFilterUInt16_Size4;
- typedef ModeFilter<uint16_t,5> ModeFilterUInt16_Size5;
- typedef ModeFilter<uint16_t,6> ModeFilterUInt16_Size6;
- typedef ModeFilter<uint16_t,7> ModeFilterUInt16_Size7;
- typedef ModeFilter<float,3> ModeFilterFloat_Size3;
- typedef ModeFilter<float,4> ModeFilterFloat_Size4;
- typedef ModeFilter<float,5> ModeFilterFloat_Size5;
- typedef ModeFilter<float,6> ModeFilterFloat_Size6;
- typedef ModeFilter<float,7> ModeFilterFloat_Size7;
- // Constructor //////////////////////////////////////////////////////////////
- template <class T, uint8_t FILTER_SIZE>
- ModeFilter<T,FILTER_SIZE>::ModeFilter(uint8_t return_element) :
- FilterWithBuffer<T,FILTER_SIZE>(),
- _return_element(return_element),
- drop_high_sample(true)
- {
- // ensure we have a valid return_nth_element value. if not, revert to median
- if( _return_element >= FILTER_SIZE )
- _return_element = FILTER_SIZE / 2;
- };
- // Public Methods //////////////////////////////////////////////////////////////
- template <class T, uint8_t FILTER_SIZE>
- T ModeFilter<T,FILTER_SIZE>:: apply(T sample)
- {
- // insert the new items into the samples buffer
- isort(sample, drop_high_sample);
- // next time drop from the other end of the sample buffer
- drop_high_sample = !drop_high_sample;
- // return results
- if( FilterWithBuffer<T,FILTER_SIZE>::sample_index < FILTER_SIZE ) {
- // middle sample if buffer is not yet full
- return _output = FilterWithBuffer<T,FILTER_SIZE>::samples[(FilterWithBuffer<T,FILTER_SIZE>::sample_index / 2)];
- }else{
- // return element specified by user in constructor
- return _output = FilterWithBuffer<T,FILTER_SIZE>::samples[_return_element];
- }
- }
- //
- // insertion sort - takes a new sample and pushes it into the sample array
- // drops either the highest or lowest sample depending on the 'drop_high_sample' parameter
- //
- template <class T, uint8_t FILTER_SIZE>
- void ModeFilter<T,FILTER_SIZE>:: isort(T new_sample, bool drop_high)
- {
- int8_t i;
- // if the buffer isn't full simply increase the #items in the buffer (i.e. sample_index)
- // the rest is the same as dropping the high sample
- if( FilterWithBuffer<T,FILTER_SIZE>::sample_index < FILTER_SIZE ) {
- FilterWithBuffer<T,FILTER_SIZE>::sample_index++;
- drop_high = true;
- }
- if( drop_high ) { // drop highest sample from the buffer to make room for our new sample
- // start from top. Note: sample_index always points to the next open space so we start from sample_index-1
- i = FilterWithBuffer<T,FILTER_SIZE>::sample_index-1;
- // if the next element is higher than our new sample, push it up one position
- while(i > 0 && FilterWithBuffer<T,FILTER_SIZE>::samples[i-1] > new_sample) {
- FilterWithBuffer<T,FILTER_SIZE>::samples[i] = FilterWithBuffer<T,FILTER_SIZE>::samples[i-1];
- i--;
- }
- // add our new sample to the buffer
- FilterWithBuffer<T,FILTER_SIZE>::samples[i] = new_sample;
- }else{ // drop lowest sample from the buffer to make room for our new sample
- // start from the bottom
- i = 0;
- // if the element is lower than our new sample, push it down one position
- while( FilterWithBuffer<T,FILTER_SIZE>::samples[i+1] < new_sample && i < FilterWithBuffer<T,FILTER_SIZE>::sample_index-1 ) {
- FilterWithBuffer<T,FILTER_SIZE>::samples[i] = FilterWithBuffer<T,FILTER_SIZE>::samples[i+1];
- i++;
- }
- // add our new sample to the buffer
- FilterWithBuffer<T,FILTER_SIZE>::samples[i] = new_sample;
- }
- }
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