MAX30102心率血氧算法

/** \file algorithm.cpp ****************************************************** * * Project: MAXREFDES117# * Filename: algorithm.cpp * Description: This module calculates the heart rate/SpO2 level * * * -------------------------------------------------------------------- * * This code follows the following naming conventions: * * char ch_pmod_value * char (array) s_pmod_s_string[16] * float f_pmod_value * int32_t n_pmod_value * int32_t (array) an_pmod_value[16] * int16_t w_pmod_value * int16_t (array) aw_pmod_value[16] * uint16_t uw_pmod_value * uint16_t (array) auw_pmod_value[16] * uint8_t uch_pmod_value * uint8_t (array) auch_pmod_buffer[16] * uint32_t un_pmod_value * int32_t * pn_pmod_value * * ------------------------------------------------------------------------- */ /******************************************************************************* * Copyright (C) 2016 Maxim Integrated Products, Inc., 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 MAXIM INTEGRATED 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. * * Except as contained in this notice, the name of Maxim Integrated * Products, Inc. shall not be used except as stated in the Maxim Integrated * Products, Inc. Branding Policy. * * 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. Maxim Integrated Products, Inc. retains all * ownership rights. ******************************************************************************* */ #include "algorithm.h" #include "mbed.h" void maxim_heart_rate_and_oxygen_saturation(uint32_t *pun_ir_buffer, int32_t n_ir_buffer_length, uint32_t *pun_red_buffer, int32_t *pn_spo2, int8_t *pch_spo2_valid, int32_t *pn_heart_rate, int8_t *pch_hr_valid) /** * \brief Calculate the heart rate and SpO2 level * \par Details * By detecting peaks of PPG cycle and corresponding AC/DC of red/infra-red signal, the ratio for the SPO2 is computed. * Since this algorithm is aiming for Arm M0/M3. formaula for SPO2 did not achieve the accuracy due to register overflow. * Thus, accurate SPO2 is precalculated and save longo uch_spo2_table[] per each ratio. * * \param[in] *pun_ir_buffer - IR sensor data buffer * \param[in] n_ir_buffer_length - IR sensor data buffer length * \param[in] *pun_red_buffer - Red sensor data buffer * \param[out] *pn_spo2 - Calculated SpO2 value * \param[out] *pch_spo2_valid - 1 if the calculated SpO2 value is valid * \param[out] *pn_heart_rate - Calculated heart rate value * \param[out] *pch_hr_valid - 1 if the calculated heart rate value is valid * * \retval None */ { uint32_t un_ir_mean ,un_only_once ; int32_t k ,n_i_ratio_count; int32_t i,s ,m, n_exact_ir_valley_locs_count ,n_middle_idx; int32_t n_th1, n_npks,n_c_min; int32_t an_ir_valley_locs[15] ; int32_t an_exact_ir_valley_locs[15] ; int32_t an_dx_peak_locs[15] ; int32_t n_peak_interval_sum; int32_t n_y_ac, n_x_ac; int32_t n_spo2_calc; int32_t n_y_dc_max, n_x_dc_max; int32_t n_y_dc_max_idx, n_x_dc_max_idx; int32_t an_ratio[5],n_ratio_average; int32_t n_nume, n_denom ; // remove DC of ir signal //去直流 un_ir_mean =0; for (k=0 ; k<n_ir_buffer_length ; k++ ) un_ir_mean += pun_ir_buffer[k] ; un_ir_mean =un_ir_mean/n_ir_buffer_length ; //求红外平均值 for (k=0 ; k<n_ir_buffer_length ; k++ ) an_x[k] = pun_ir_buffer[k] - un_ir_mean ; // 4 pt Moving Average 4项与平均数差值的平均数 for(k=0; k< BUFFER_SIZE-MA4_SIZE; k++){ n_denom= ( an_x[k]+an_x[k+1]+ an_x[k+2]+ an_x[k+3]); an_x[k]= n_denom/(int32_t)4; } // get difference of smoothed IR signal for( k=0; k<BUFFER_SIZE-MA4_SIZE-1; k++) an_dx[k]= (an_x[k+1]- an_x[k]); // 2-pt Moving Average to an_dx for(k=0; k< BUFFER_SIZE-MA4_SIZE-2; k++){ an_dx[k] = ( an_dx[k]+an_dx[k+1])/2 ; } // hamming window构造一个函数。这个函数在某一区间有非零值，而在其余区间皆为0.汉明窗就是这样的一种函数 // flip wave form so that we can detect valley with peak detector //翻转波形，就能利用波峰探测器探测到波谷 for ( i=0 ; i<BUFFER_SIZE-HAMMING_SIZE-MA4_SIZE-2 ;i++){ s= 0; for( k=i; k<i+ HAMMING_SIZE ;k++){ s -= an_dx[k] *auw_hamm[k-i] ; } an_dx[i]= s/ (int32_t)1146; // divide by sum of auw_hamm } n_th1=0; // threshold calculation阈值计算 for ( k=0 ; k<BUFFER_SIZE-HAMMING_SIZE ;k++){ n_th1 += ((an_dx[k]>0)? an_dx[k] : ((int32_t)0-an_dx[k])) ; } n_th1= n_th1/ ( BUFFER_SIZE-HAMMING_SIZE); // peak location is acutally index for sharpest location of raw signal since we flipped the signal maxim_find_peaks( an_dx_peak_locs, &n_npks, an_dx, BUFFER_SIZE-HAMMING_SIZE, n_th1, 8, 5 );//peak_height, peak_distance, max_num_peaks n_peak_interval_sum =0; if (n_npks>=2){ for (k=1; k<n_npks; k++) n_peak_interval_sum += (an_dx_peak_locs[k]-an_dx_peak_locs[k -1]); n_peak_interval_sum=n_peak_interval_sum/(n_npks-1); *pn_heart_rate=(int32_t)(6000/n_peak_interval_sum);// beats per minutes 一分钟采集6000个样本，除以峰峰之间平均样本数 *pch_hr_valid = 1; } else { *pn_heart_rate = -999; *pch_hr_valid = 0; } for ( k=0 ; k<n_npks ;k++) an_ir_valley_locs[k]=an_dx_peak_locs[k]+HAMMING_SIZE/2; // raw value : RED(=y) and IR(=X) // we need to assess DC and AC value of ir and red PPG. for (k=0 ; k<n_ir_buffer_length ; k++ ) { an_x[k] = pun_ir_buffer[k] ; an_y[k] = pun_red_buffer[k] ; } // find precise min near an_ir_valley_locs n_exact_ir_valley_locs_count =0; for(k=0 ; k<n_npks ;k++){ un_only_once =1; m=an_ir_valley_locs[k]; n_c_min= 16777216;//2^24; if (m+5 < BUFFER_SIZE-HAMMING_SIZE && m-5 >0){ for(i= m-5;i<m+5; i++) if (an_x[i]<n_c_min){ if (un_only_once >0){ un_only_once =0; } n_c_min= an_x[i] ; an_exact_ir_valley_locs[k]=i; } if (un_only_once ==0) n_exact_ir_valley_locs_count ++ ; } } if (n_exact_ir_valley_locs_count <2 ){ *pn_spo2 = -999 ; // do not use SPO2 since signal rati