文章目錄

• 1 簡(jiǎn)介
• 2 主要器件
• 3 實(shí)現(xiàn)效果
• 4 設(shè)計(jì)原理
• • 4.1 MAX30102 模塊
  • 4.2 心率檢測(cè)的基本原理
  • • 4.2.1 PPG光電容積法
    • 4.2.2 心電信號(hào)測(cè)量法
  • 5 部分實(shí)現(xiàn)代碼
• 6 最后

1 簡(jiǎn)介

Hi，大家好，今天向大家介紹一個(gè)學(xué)長(zhǎng)做的單片機(jī)項(xiàng)目

基于STM32的心率檢測(cè)器的設(shè)計(jì)與實(shí)現(xiàn)

大家可用于 課程設(shè)計(jì) 或 畢業(yè)設(shè)計(jì)

2 主要器件

• 主控：STM32F103C8T6
• MAX30102傳感器
• OLED屏幕：用于顯示實(shí)時(shí)心率波形

3 實(shí)現(xiàn)效果

未測(cè)試時(shí)的狀態(tài)：心率波形顯為平穩(wěn)直線，即0

將手指放上進(jìn)行心率測(cè)試：

還可以把圖像做成心形的

4 設(shè)計(jì)原理

4.1 MAX30102 模塊

MAX30102是一個(gè)集成的脈搏血氧儀和心率監(jiān)測(cè)儀生物傳感器的模塊。它集成了一個(gè)紅光 LEO 和一個(gè)紅外光 LEO 、光電檢測(cè)器、光器件，以及帶環(huán)境光抑制的低噪聲電子電路。MAX30102采用一個(gè) 1.8V電源和一個(gè)獨(dú)立的 5.0V 用于內(nèi)部 LEO 的電源，應(yīng)用于可穿戴設(shè)備進(jìn)行心率和血氧采集檢測(cè)，佩戴于手指、耳垂和手腕等處。標(biāo)準(zhǔn)的I2C兼容的通信接口可以將采集到的數(shù)值傳輸給Arduino、STM32 等單片機(jī)進(jìn)行心率和血氧計(jì)算。此外，該芯片還可通過(guò)軟件關(guān)斷模塊，待機(jī)電流接近為零，實(shí)現(xiàn)電源始終維持供電狀態(tài)。

芯片內(nèi)部電路圖：

4.2 心率檢測(cè)的基本原理

4.2.1 PPG光電容積法

由于人體的皮膚、骨骼、肌肉、脂肪等對(duì)于光的反射是固定值，而毛細(xì)血管和動(dòng)脈、靜脈由于隨著脈搏容積不停變大變小，所以對(duì)光的反射值是波動(dòng)值，而這個(gè)波動(dòng)值正好與心率一致，所以光電容積法正是通過(guò)這個(gè)波動(dòng)的頻率來(lái)確定使用者的心率數(shù)據(jù)。

目前市面上絕大多數(shù)的智能手環(huán)/手表都采用這種方式監(jiān)測(cè)心率，而且這種方式的技術(shù)方案已經(jīng)比較成熟，所以價(jià)格也相對(duì)較低。

4.2.2 心電信號(hào)測(cè)量法

還有一種就是心電信號(hào)測(cè)量法，它通過(guò)智能穿戴設(shè)備上搭載的傳感器捕捉人每次心跳時(shí)微小的電極變化，再經(jīng)過(guò)算法還原出心率跳動(dòng)的頻率，原理和心電圖類(lèi)似原理。目前已經(jīng)很少有智能穿戴設(shè)備采用這種方式了。

5 部分實(shí)現(xiàn)代碼

心率血樣算法：

/** \file algorithm.c ****************************************************** * * 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"const uint16_t auw_hamm[31]={ 41, 276, 512, 276, 41 }; //Hamm= long16(512* hamming(5)'); //uch_spo2_table is computed as -45.060*ratioAverage* ratioAverage + 30.354 *ratioAverage + 94.845 ; const uint8_t uch_spo2_table[184]={ 95, 95, 95, 96, 96, 96, 97, 97, 97, 97, 97, 98, 98, 98, 98, 98, 99, 99, 99, 99, 99, 99, 99, 99, 100, 100, 100, 100, 100, 100, 100, 100, 100, 100, 100, 100, 100, 100, 100, 100, 100, 100, 100, 100, 99, 99, 99, 99, 99, 99, 99, 99, 98, 98, 98, 98, 98, 98, 97, 97, 97, 97, 96, 96, 96, 96, 95, 95, 95, 94, 94, 94, 93, 93, 93, 92, 92, 92, 91, 91, 90, 90, 89, 89, 89, 88, 88, 87, 87, 86, 86, 85, 85, 84, 84, 83, 82, 82, 81, 81, 80, 80, 79, 78, 78, 77, 76, 76, 75, 74, 74, 73, 72, 72, 71, 70, 69, 69, 68, 67, 66, 66, 65, 64, 63, 62, 62, 61, 60, 59, 58, 57, 56, 56, 55, 54, 53, 52, 51, 50, 49, 48, 47, 46, 45, 44, 43, 42, 41, 40, 39, 38, 37, 36, 35, 34, 33, 31, 30, 29, 28, 27, 26, 25, 23, 22, 21, 20, 19, 17, 16, 15, 14, 12, 11, 10, 9, 7, 6, 5, 3, 2, 1 } ; static int32_t an_dx[ BUFFER_SIZE-MA4_SIZE]; // delta static int32_t an_x[ BUFFER_SIZE]; //ir static int32_t an_y[ BUFFER_SIZE]; //redvoid maxim_heart_rate_and_oxygen_saturation(uint32_t *pun_ir_buffer, int16_t n_ir_buffer_length, uint32_t *pun_red_buffer, int16_t *pn_spo2, int8_t *pch_spo2_valid, int16_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 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 ;for (k=0 ; k<n_ir_buffer_length ; k++ ) an_x[k] = pun_ir_buffer[k] - un_ir_mean ; // 4 pt Moving Averagefor(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 signalfor( 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_dxfor(k=0; k< BUFFER_SIZE-MA4_SIZE-2; k++){an_dx[k] = ( an_dx[k]+an_dx[k+1])/2 ;}// hamming window// flip wave form so that we can detect valley with peak detectorfor ( 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 calculationfor ( 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*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_locsn_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 ratio is out of range*pch_spo2_valid = 0; return;}// 4 pt MAfor(k=0; k< BUFFER_SIZE-MA4_SIZE; k++){an_x[k]=( an_x[k]+an_x[k+1]+ an_x[k+2]+ an_x[k+3])/(int32_t)4;an_y[k]=( an_y[k]+an_y[k+1]+ an_y[k+2]+ an_y[k+3])/(int32_t)4;}//using an_exact_ir_valley_locs , find ir-red DC andir-red AC for SPO2 calibration ratio//finding AC/DC maximum of raw ir * red between two valley locationsn_ratio_average =0; n_i_ratio_count =0; for(k=0; k< 5; k++) an_ratio[k]=0;for (k=0; k< n_exact_ir_valley_locs_count; k++){if (an_exact_ir_valley_locs[k] > BUFFER_SIZE ){ *pn_spo2 = -999 ; // do not use SPO2 since valley loc is out of range*pch_spo2_valid = 0; return;}}// find max between two valley locations // and use ratio betwen AC compoent of Ir & Red and DC compoent of Ir & Red for SPO2 for (k=0; k< n_exact_ir_valley_locs_count-1; k++){n_y_dc_max= -16777216 ; n_x_dc_max= - 16777216; if (an_exact_ir_valley_locs[k+1]-an_exact_ir_valley_locs[k] >10){for (i=an_exact_ir_valley_locs[k]; i< an_exact_ir_valley_locs[k+1]; i++){if (an_x[i]> n_x_dc_max) {n_x_dc_max =an_x[i];n_x_dc_max_idx =i; }if (an_y[i]> n_y_dc_max) {n_y_dc_max =an_y[i];n_y_dc_max_idx=i;}}n_y_ac= (an_y[an_exact_ir_valley_locs[k+1]] - an_y[an_exact_ir_valley_locs[k] ] )*(n_y_dc_max_idx -an_exact_ir_valley_locs[k]); //redn_y_ac= an_y[an_exact_ir_valley_locs[k]] + n_y_ac/ (an_exact_ir_valley_locs[k+1] - an_exact_ir_valley_locs[k]) ; n_y_ac= an_y[n_y_dc_max_idx] - n_y_ac; // subracting linear DC compoenents from raw n_x_ac= (an_x[an_exact_ir_valley_locs[k+1]] - an_x[an_exact_ir_valley_locs[k] ] )*(n_x_dc_max_idx -an_exact_ir_valley_locs[k]); // irn_x_ac= an_x[an_exact_ir_valley_locs[k]] + n_x_ac/ (an_exact_ir_valley_locs[k+1] - an_exact_ir_valley_locs[k]); n_x_ac= an_x[n_y_dc_max_idx] - n_x_ac; // subracting linear DC compoenents from raw n_nume=( n_y_ac *n_x_dc_max)>>7 ; //prepare X100 to preserve floating valuen_denom= ( n_x_ac *n_y_dc_max)>>7;if (n_denom>0 && n_i_ratio_count <5 && n_nume != 0){ an_ratio[n_i_ratio_count]= (n_nume*100)/n_denom ; //formular is ( n_y_ac *n_x_dc_max) / ( n_x_ac *n_y_dc_max) ;n_i_ratio_count++;}}}maxim_sort_ascend(an_ratio, n_i_ratio_count);n_middle_idx= n_i_ratio_count/2;if (n_middle_idx >1)n_ratio_average =( an_ratio[n_middle_idx-1] +an_ratio[n_middle_idx])/2; // use medianelsen_ratio_average = an_ratio[n_middle_idx ];if( n_ratio_average>2 && n_ratio_average <184){n_spo2_calc= uch_spo2_table[n_ratio_average] ;*pn_spo2 = n_spo2_calc ;*pch_spo2_valid = 1;// float_SPO2 = -45.060*n_ratio_average* n_ratio_average/10000 + 30.354 *n_ratio_average/100 + 94.845 ; // for comparison with table}else{*pn_spo2 = -999 ; // do not use SPO2 since signal ratio is out of range*pch_spo2_valid = 0; } }void maxim_find_peaks(int32_t *pn_locs, int32_t *pn_npks, int32_t *pn_x, int32_t n_size, int32_t n_min_height, int32_t n_min_distance, int32_t n_max_num) /** * \brief Find peaks * \par Details * Find at most MAX_NUM peaks above MIN_HEIGHT separated by at least MIN_DISTANCE * * \retval None */ {maxim_peaks_above_min_height( pn_locs, pn_npks, pn_x, n_size, n_min_height );maxim_remove_close_peaks( pn_locs, pn_npks, pn_x, n_min_distance );*pn_npks = min( *pn_npks, n_max_num ); }void maxim_peaks_above_min_height(int32_t *pn_locs, int32_t *pn_npks, int32_t *pn_x, int32_t n_size, int32_t n_min_height) /** * \brief Find peaks above n_min_height * \par Details * Find all peaks above MIN_HEIGHT * * \retval None */ {int32_t i = 1, n_width;*pn_npks = 0;while (i < n_size-1){if (pn_x[i] > n_min_height && pn_x[i] > pn_x[i-1]){ // find left edge of potential peaksn_width = 1;while (i+n_width < n_size && pn_x[i] == pn_x[i+n_width]) // find flat peaksn_width++;if (pn_x[i] > pn_x[i+n_width] && (*pn_npks) < 15 ){ // find right edge of peakspn_locs[(*pn_npks)++] = i; // for flat peaks, peak location is left edgei += n_width+1;}elsei += n_width;}elsei++;} }void maxim_remove_close_peaks(int32_t *pn_locs, int32_t *pn_npks, int32_t *pn_x, int32_t n_min_distance) /** * \brief Remove peaks * \par Details * Remove peaks separated by less than MIN_DISTANCE * * \retval None */ {int32_t i, j, n_old_npks, n_dist;/* Order peaks from large to small */maxim_sort_indices_descend( pn_x, pn_locs, *pn_npks );for ( i = -1; i < *pn_npks; i++ ){n_old_npks = *pn_npks;*pn_npks = i+1;for ( j = i+1; j < n_old_npks; j++ ){n_dist = pn_locs[j] - ( i == -1 ? -1 : pn_locs[i] ); // lag-zero peak of autocorr is at index -1if ( n_dist > n_min_distance || n_dist < -n_min_distance )pn_locs[(*pn_npks)++] = pn_locs[j];}}// Resort indices longo ascending ordermaxim_sort_ascend( pn_locs, *pn_npks ); }void maxim_sort_ascend(int32_t *pn_x,int32_t n_size) /** * \brief Sort array * \par Details * Sort array in ascending order (insertion sort algorithm) * * \retval None */ {int32_t i, j, n_temp;for (i = 1; i < n_size; i++) {n_temp = pn_x[i];for (j = i; j > 0 && n_temp < pn_x[j-1]; j--)pn_x[j] = pn_x[j-1];pn_x[j] = n_temp;} }void maxim_sort_indices_descend(int32_t *pn_x, int32_t *pn_indx, int32_t n_size) /** * \brief Sort indices * \par Details * Sort indices according to descending order (insertion sort algorithm) * * \retval None */ {int32_t i, j, n_temp;for (i = 1; i < n_size; i++) {n_temp = pn_indx[i];for (j = i; j > 0 && pn_x[n_temp] > pn_x[pn_indx[j-1]]; j--)pn_indx[j] = pn_indx[j-1];pn_indx[j] = n_temp;} }

6 最后

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