Line data    Source code

       1             : /*
       2             :    This program is free software: you can redistribute it and/or modify
       3             :    it under the terms of the GNU General Public License as published by
       4             :    the Free Software Foundation, either version 3 of the License, or
       5             :    (at your option) any later version.
       6             : 
       7             :    This program is distributed in the hope that it will be useful,
       8             :    but WITHOUT ANY WARRANTY; without even the implied warranty of
       9             :    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
      10             :    GNU General Public License for more details.
      11             : 
      12             :    You should have received a copy of the GNU General Public License
      13             :    along with this program.  If not, see <http://www.gnu.org/licenses/>.
      14             :  */
      15             : 
      16             : //
      17             : /// @file       Derivative.h
      18             : /// @brief      A class to implement a derivative (slope) filter
      19             : /// See http://www.holoborodko.com/pavel/numerical-methods/numerical-derivative/smooth-low-noise-differentiators/
      20             : #pragma once
      21             : 
      22             : #include "FilterClass.h"
      23             : #include "FilterWithBuffer.h"
      24             : 
      25             : // 1st parameter <T> is the type of data being filtered.
      26             : // 2nd parameter <FILTER_SIZE> is the number of elements in the filter
      27             : template <class T, uint8_t FILTER_SIZE>
      28             : class DerivativeFilter : public FilterWithBuffer<T,FILTER_SIZE>
      29             : {
      30             : public:
      31             :     // constructor
      32        3387 :     DerivativeFilter() : FilterWithBuffer<T,FILTER_SIZE>() {
      33        3387 :     };
      34             : 
      35             :     // update - Add a new raw value to the filter, but don't recalculate
      36             :     void update(T sample, uint32_t timestamp);
      37             : 
      38             :     // return the derivative value
      39             :     float slope(void);
      40             : 
      41             :     // reset - clear the filter
      42             :     virtual void        reset() override;
      43             : 
      44             : private:
      45             :     bool            _new_data;
      46             :     float           _last_slope;
      47             : 
      48             :     // microsecond timestamps for samples. This is needed
      49             :     // to cope with non-uniform time spacing of the data
      50             :     uint32_t        _timestamps[FILTER_SIZE];
      51             : };
      52             : 
      53             : typedef DerivativeFilter<float,5> DerivativeFilterFloat_Size5;
      54             : typedef DerivativeFilter<float,7> DerivativeFilterFloat_Size7;
      55             : typedef DerivativeFilter<float,9> DerivativeFilterFloat_Size9;