File content as of revision 0:010b908e2187:

/*
Arduino-MAX30100 oximetry / heart rate integrated sensor library
Copyright (C) 2016  OXullo Intersecans <x@brainrapers.org>
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/>.
*/

#ifndef MAX30100_BEATDETECTOR_H
#define MAX30100_BEATDETECTOR_H

#include "mbed.h"
#include <stdint.h>
#include <algorithm>

#define BEATDETECTOR_INIT_HOLDOFF                2000    // in ms, how long to wait before counting
#define BEATDETECTOR_MASKING_HOLDOFF             200     // in ms, non-retriggerable window after beat detection
#define BEATDETECTOR_BPFILTER_ALPHA              0.6     // EMA factor for the beat period value
#define BEATDETECTOR_MIN_THRESHOLD               20      // minimum threshold (filtered) value
#define BEATDETECTOR_MAX_THRESHOLD               800     // maximum threshold (filtered) value
#define BEATDETECTOR_STEP_RESILIENCY             30      // maximum negative jump that triggers the beat edge
#define BEATDETECTOR_THRESHOLD_FALLOFF_TARGET    0.3     // thr chasing factor of the max value when beat
#define BEATDETECTOR_THRESHOLD_DECAY_FACTOR      0.99    // thr chasing factor when no beat
#define BEATDETECTOR_INVALID_READOUT_DELAY       2000    // in ms, no-beat time to cause a reset
#define BEATDETECTOR_SAMPLES_PERIOD              10      // in ms, 1/Fs


typedef enum BeatDetectorState {
    BEATDETECTOR_STATE_INIT,
    BEATDETECTOR_STATE_WAITING,
    BEATDETECTOR_STATE_FOLLOWING_SLOPE,
    BEATDETECTOR_STATE_MAYBE_DETECTED,
    BEATDETECTOR_STATE_MASKING
} BeatDetectorState;


class BeatDetector
{
public:
    BeatDetector();
    bool addSample(float sample);
    float getRate();
    float getCurrentThreshold();

private:
    bool checkForBeat(float value);
    void decreaseThreshold();

    BeatDetectorState state;
    float threshold;
    float beatPeriod;
    float lastMaxValue;
    uint32_t tsLastBeat;
    Timer t;
};

#endif