MAX30100_Filters.h

00001 /*
00002 Arduino-MAX30100 oximetry / heart rate integrated sensor library
00003 Copyright (C) 2016  OXullo Intersecans <x@brainrapers.org>
00004 This program is free software: you can redistribute it and/or modify
00005 it under the terms of the GNU General Public License as published by
00006 the Free Software Foundation, either version 3 of the License, or
00007 (at your option) any later version.
00008 This program is distributed in the hope that it will be useful,
00009 but WITHOUT ANY WARRANTY; without even the implied warranty of
00010 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
00011 GNU General Public License for more details.
00012 You should have received a copy of the GNU General Public License
00013 along with this program.  If not, see <http://www.gnu.org/licenses/>.
00014 */
00015 
00016 #ifndef MAX30100_FILTERS_H
00017 #define MAX30100_FILTERS_H
00018 
00019 // http://www.schwietering.com/jayduino/filtuino/
00020 // Low pass butterworth filter order=1 alpha1=0.1
00021 // Fs=100Hz, Fc=6Hz
00022 class  FilterBuLp1
00023 {
00024     public:
00025         FilterBuLp1()
00026         {
00027             v[0]=0.0;
00028         }
00029     private:
00030         float v[2];
00031     public:
00032         float step(float x) //class II
00033         {
00034             v[0] = v[1];
00035             v[1] = (2.452372752527856026e-1 * x)
00036                  + (0.50952544949442879485 * v[0]);
00037             return
00038                  (v[0] + v[1]);
00039         }
00040 };
00041 
00042 // http://sam-koblenski.blogspot.de/2015/11/everyday-dsp-for-programmers-dc-and.html
00043 class DCRemover
00044 {
00045 public:
00046     DCRemover() : alpha(0), dcw(0)
00047     {
00048     }
00049     DCRemover(float alpha_) : alpha(alpha_), dcw(0)
00050     {
00051     }
00052 
00053     float step(float x)
00054     {
00055         float olddcw = dcw;
00056         dcw = (float)x + alpha * dcw;
00057 
00058         return dcw - olddcw;
00059     }
00060 
00061     float getDCW()
00062     {
00063         return dcw;
00064     }
00065 
00066 private:
00067     float alpha;
00068     float dcw;
00069 };
00070 
00071 #endif