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algorithm_by_RF.h
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/*
* Created by Robert Fraczkiewicz, 01/2018
* New signal processing methodology for obtaining heart rate and SpO2 data
* from the MAX30102 sensor manufactured by MAXIM Integrated Products, Inc.
*/
/*******************************************************************************
* Copyright (C) 2017 Robert Fraczkiewicz, All Rights Reserved.
*
* Permission is hereby granted, free of charge, to any person obtaining a
* copy of this software and associated documentation files (the "Software"),
* to deal in the Software without restriction, including without limitation
* the rights to use, copy, modify, merge, publish, distribute, sublicense,
* and/or sell copies of the Software, and to permit persons to whom the
* Software is furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included
* in all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
* OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
* IN NO EVENT SHALL ROBERT FRACZKIEWICZ BE LIABLE FOR ANY CLAIM, DAMAGES
* OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
* ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
* OTHER DEALINGS IN THE SOFTWARE.
*
* The mere transfer of this software does not imply any licenses
* of trade secrets, proprietary technology, copyrights, patents,
* trademarks, maskwork rights, or any other form of intellectual
* property whatsoever. Robert Fraczkiewicz retains all
* ownership rights.
*******************************************************************************
*/
#ifndef ALGORITHM_BY_RF_H_
#define ALGORITHM_BY_RF_H_
#include <Arduino.h>
/*
* Settable parameters
* Leave these alone if your circuit and hardware setup match the defaults
* described in this code's Instructable. Typically, different sampling rate
* and/or sample length would require these paramteres to be adjusted.
*/
// HN changed FS to 50Hz
#define ST 4 // Sampling time in s. WARNING: if you change ST, then you MUST recalcuate the sum_X2 parameter below!
#define FS 50 // Sampling frequency in Hz. WARNING: if you change FS, then you MUST recalcuate the sum_X2 parameter below!
// Sum of squares of ST*FS numbers from -mean_X (see below) to +mean_X incremented be one. For example, given ST=4 and FS=50,
// the sum consists of 200 terms: (-99.5)^2 + (-98.5)^2 + (-97.5)^2 + ... + (97.5)^2 + (98.5)^2 + (99.5)^2
// The sum is symmetrc, so you can evaluate it by multiplying its positive half by 2. It is precalcuated here for enhanced
// performance.
const float sum_X2 = 666650.0; // WARNING: you MUST recalculate this sum if you changed either ST or FS above!
// WARNING: The two parameters below are CRUCIAL! Proper HR evaluation depends on these.
#define MAX_HR 180 // Maximal heart rate. To eliminate erroneous signals, calculated HR should never be greater than this number.
#define MIN_HR 40 // Minimal heart rate. To eliminate erroneous signals, calculated HR should never be lower than this number.
// Minimal ratio of two autocorrelation sequence elements: one at a considered lag to the one at lag 0.
// Good quality signals must have such ratio greater than this minimum.
const float min_autocorrelation_ratio = 0.5;
// Pearson correlation between red and IR signals.
// Good quality signals must have their correlation coefficient greater than this minimum.
const float min_pearson_correlation = 0.8;
/*
* Derived parameters
* Do not touch these!
*
*/
const int32_t RFA_BUFFER_SIZE = FS*ST; // Number of smaples in a single batch
const int32_t FS60 = FS*60; // Conversion factor for heart rate from bps to bpm
const int32_t LOWEST_PERIOD = FS60/MAX_HR; // Minimal distance between peaks
const int32_t HIGHEST_PERIOD = FS60/MIN_HR; // Maximal distance between peaks
const float mean_X = (float)(RFA_BUFFER_SIZE-1)/2.0; // Mean value of the set of integers from 0 to RFA_BUFFER_SIZE-1. For ST=4 and FS=50 it's equal to 99.5.
void rf_heart_rate_and_oxygen_saturation(uint32_t *pun_ir_buffer, int32_t n_ir_buffer_length, uint32_t *pun_red_buffer, float *pn_spo2, int8_t *pch_spo2_valid, int32_t *pn_heart_rate,
int8_t *pch_hr_valid, float *ratio, float *correl);
float rf_linear_regression_beta(float *pn_x, float xmean, float sum_x2);
float rf_autocorrelation(float *pn_x, int32_t n_size, int32_t n_lag);
float rf_rms(float *pn_x, int32_t n_size, float *sumsq);
float rf_Pcorrelation(float *pn_x, float *pn_y, int32_t n_size);
void rf_initialize_periodicity_search(float *pn_x, int32_t n_size, int32_t *p_last_periodicity, int32_t n_max_distance, float min_aut_ratio, float aut_lag0);
void rf_signal_periodicity(float *pn_x, int32_t n_size, int32_t *p_last_periodicity, int32_t n_min_distance, int32_t n_max_distance, float min_aut_ratio, float aut_lag0, float *ratio);
#endif /* ALGORITHM_BY_RF_H_ */