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基于stm32及Max30102的心率血氧检测cubemx生成_max30102心率算法

作者：盐析白兔 | 2024-05-18 22:03:13

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max30102心率算法

一、前言

Max30102是一款集成了红外发光二极管、光电检测器、信号处理和数据输出功能于一体的脉搏血氧测量模块。它能够通过皮肤进行非侵入式的心率和血氧饱和度监测，常被用于可穿戴设备或医疗设备中。Max30102具有高精度、低功耗和小尺寸的特点，广泛应用于健康监测领域。于是准备做个监测心率血氧的小型设备。

二、准备

硬件：stm32f103c8t6,MAX30102,0.96寸OLED

软件：keil5

三、cubemx配置工程文件

配置SYS,RCC,时钟数，I2C1(用于OLED),I2C2(用于MAX30102),GPIO

PA7配置为INT引脚，输入模式，配上拉电阻（INT默认高电平，低电平有效）

I2C1和I2C2都配置为高速I2C(只为了更快)

生成工程文件

生成并进入工程文件

四、MAX30102驱动

4.1 读取FIFO函数


//写Data到max30102中
HAL_StatusTypeDef Max30102_WriteData(uint8_t MemAddress,uint8_t Command,uint16_t SendCount)
{
	HAL_StatusTypeDef status=HAL_OK;
	status=HAL_I2C_Mem_Write(&hi2c2,Max30102_Write_Address,MemAddress,I2C_MEMADD_SIZE_8BIT,&Command,SendCount,100);
	return status;
}
 
//I2C读取函数
HAL_StatusTypeDef Max30102_ReadData(uint8_t DatAddress,uint8_t *Data,uint16_t ReceiveCount)
{
	HAL_StatusTypeDef status=HAL_OK;
	status=HAL_I2C_Mem_Read(&hi2c2,Max30102_Read_Address,DatAddress,I2C_MEMADD_SIZE_8BIT,Data,ReceiveCount,100);
	return status;
}
 
void Max30102_FIFO_ReadData(uint8_t DatAddress,uint8_t SixData[6],uint16_t Size)
{
	uint8_t temp;
	Max30102_ReadData(REG_INTR_STATUS_1,&temp,1);
	Max30102_ReadData(REG_INTR_STATUS_2,&temp,1);
	Max30102_ReadData(DatAddress,SixData,Size);
}

4.2 MAX30102初始化


void Max30102_Reset(void)
{
	Max30102_WriteData(REG_MODE_CONFIG,0x40,1);
	Max30102_WriteData(REG_MODE_CONFIG,0x40,1);
}
 
void Max30102_Init(void)
{
	Max30102_Reset();
	
	Max30102_WriteData(REG_INTR_ENABLE_1,0xc0,1);	// INTR setting
	Max30102_WriteData(REG_INTR_ENABLE_2,0x00,1);
	Max30102_WriteData(REG_FIFO_WR_PTR,0x00,1);  	//FIFO_WR_PTR[4:0]
	Max30102_WriteData(REG_OVF_COUNTER,0x00,1);  	//OVF_COUNTER[4:0]
	Max30102_WriteData(REG_FIFO_RD_PTR,0x00,1);  	//FIFO_RD_PTR[4:0]
	Max30102_WriteData(REG_FIFO_CONFIG,0x0f,1);  	//sample avg = 1, fifo rollover=false, fifo almost full = 17
	Max30102_WriteData(REG_MODE_CONFIG,0x03,1);  	//0x02 for Red only, 0x03 for SpO2 mode 0x07 multimode LED
	Max30102_WriteData(REG_SPO2_CONFIG,0x27,1);  	// SPO2_ADC range = 4096nA, SPO2 sample rate (100 Hz), LED pulseWidth (400uS)  
	Max30102_WriteData(REG_LED1_PA,0x24,1);   	//Choose value for ~ 7mA for LED1
	Max30102_WriteData(REG_LED2_PA,0x24,1);   	// Choose value for ~ 7mA for LED2
	Max30102_WriteData(REG_PILOT_PA,0x7f,1);   	// Choose value for ~ 25mA for Pilot LED
}

先连接好线，把初始化程序烧进去，如果MAX30102红灯亮则没问题可以继续下一步，如果红灯不亮，大概率是I2C没通，仔细检查是不是线没接好！

MAX30102接线：

SCL-----PB10 SDA-----PB11 INT-----PA7

OLED接线：

SCL-----PB6 SDA-----PB7

4.3 MAX30102算法实现心率血氧检测

在写MAX30102程序前先把下面的algorithm文件放入工程文件中并在Keil5中添加文件路径，这是一个针对于心率血氧的算法，把前辈研究好的东西拿来用也是不错的！algorithm文件中的.c和.h文件代码的代码我放在最下面。也可以直接下载我上传的文件解压即可。

链接：https://pan.baidu.com/s/1-GGcoyf4qizAIo3MfZ7qug
提取码：ae86

MAX30102心率血氧读取代码（代码以注释明确）

4.3.1 各种变量的声明


uint8_t TempData[6];
uint32_t red_buffer[500];  //红光数据red，用于计算心率
uint32_t ir_buffer[500];  //红外数据 ir，用于计算血氧
int32_t ir_buffer_length=500;   //计算前500个样本得到的数据
int32_t pn_SpO2_value;   //血氧实际值
int8_t SpO2_valid;        //血氧值有效标志
int32_t pn_hr_value;    //心率实际值
int8_t hr_valid;         //心率有效标志
uint32_t red_max=0,red_min=0x3FFFF;  //红光取值范围
uint32_t prev_data;      //前一次的值
float f_temp;           //临时变量
int32_t n_brightness;    //明确变量

4.3.2 MAX30102数据初始化函数


void Max30102_Safety(void)
{
	for(int i=0;i<ir_buffer_length;i++)
	{
		while(Max30102_INT==GPIO_PIN_SET); //等待中断引脚相应，默认为高,当触发后会拉低
		Max30102_FIFO_ReadData(REG_FIFO_DATA,TempData,6);
		red_buffer[i]=((TempData[0]&0x03)<<16) | (TempData[1]<<8) | (TempData[2]); //前三位数据组成HR
		ir_buffer[i]=((TempData[3]&0x03)<<16) | (TempData[4]<<8) | (TempData[5]); //后三位数据组成BO
		if(red_min>red_buffer[i]) red_min=red_buffer[i];  //更新当前最小值
		if(red_max<red_buffer[i]) red_max=red_buffer[i];  //更新当前最大值
	}
	maxim_heart_rate_and_oxygen_saturation(ir_buffer,ir_buffer_length,red_buffer,&pn_SpO2_value,&SpO2_valid,&pn_hr_value,&hr_valid);
	//传入500个采样，通过算法得出实际心率血氧值
}

4.3.3 心率血氧计算函数


void Max30102_Calculate_HR_BO_Value(int32_t* HR_Value,int8_t* HR_Valid,int32_t* BO_Value,int8_t* BO_Valid)
{
	for(int i=100;i<500;i++)  //将数组中的100~500采样值向前挪到0~400
	{
		red_buffer[i-100]=red_buffer[i];
		ir_buffer[i-100]=ir_buffer[i];
		if(red_min>red_buffer[i]) red_min=red_buffer[i];  //更新当前最小值
		if(red_max<red_buffer[i]) red_max=red_buffer[i];  //更新当前最大值
	}
	for(int i=400;i<500;i++)  //实际只取100个采样值来计算
	{
		prev_data=red_buffer[i-1];
		while(Max30102_INT==1); //等待中断引脚相应，默认为高,当触发后会拉低
		Max30102_FIFO_ReadData(REG_FIFO_DATA,TempData,6);
		red_buffer[i]=((TempData[0]&0x03)<<16) | (TempData[1]<<8) | (TempData[2]); //前三位数据组成HR
		ir_buffer[i]=((TempData[3]&0x03)<<16) | (TempData[4]<<8) | (TempData[5]); //后三位数据组成BO
		if(red_buffer[i]>prev_data)
		{    //心率公式：|上一次的值-当前值| / (最大值-最小值) * 255
			f_temp=(float)(red_buffer[i]-prev_data)/(red_max-red_min)*255;
			n_brightness-=(int)f_temp;
			if(n_brightness<0) n_brightness=0;
		}
		else
		{
			f_temp=(float)(prev_data-red_buffer[i])/(red_max-red_min)*255;
			n_brightness+=(int)f_temp;
			if(n_brightness>255) n_brightness=255;
		}
		*HR_Value=pn_hr_value;
		*HR_Valid=hr_valid;
		*BO_Value=pn_SpO2_value;
		*BO_Valid=SpO2_valid;
	}
	maxim_heart_rate_and_oxygen_saturation(ir_buffer,ir_buffer_length,red_buffer,&pn_SpO2_value,&SpO2_valid,&pn_hr_value,&hr_valid);
}

五、硬件I2c驱动OLED

这里我仿照了江科大老师的OLED模板，只改动了OLED.c文件：


#include "main.h"
#include "OLED_Font.h"
#include "i2c.h"
 
#define OLED0561_ADD	0x78  //OLED的I2C地址
#define COM				0x00  //OLED 指令
#define DAT 			0x40  //OLED 数据
 
void OLED_WriteCommand(uint8_t I2C_Command)//写命令
{
	HAL_I2C_Mem_Write(&hi2c1,OLED0561_ADD,COM,I2C_MEMADD_SIZE_8BIT,&I2C_Command,1,100);
}
		
void OLED_WriteData(uint8_t I2C_Data)//写数据
{
	HAL_I2C_Mem_Write(&hi2c1,OLED0561_ADD,DAT,I2C_MEMADD_SIZE_8BIT,&I2C_Data,1,100);
}
 
/**
  * @brief  OLED设置光标位置
  * @param  Y 以左上角为原点，向下方向的坐标，范围：0~7
  * @param  X 以左上角为原点，向右方向的坐标，范围：0~127
  * @retval 无
  */
void OLED_SetCursor(uint8_t Y, uint8_t X)
{
	OLED_WriteCommand(0xB0 | Y);					//设置Y位置
	OLED_WriteCommand(0x10 | ((X & 0xF0) >> 4));	//设置X位置高4位
	OLED_WriteCommand(0x00 | (X & 0x0F));			//设置X位置低4位
}
 
/**
  * @brief  OLED清屏
  * @param  无
  * @retval 无
  */
void OLED_Clear(void)
{  
	uint8_t i, j;
	for (j = 0; j < 8; j++)
	{
		OLED_SetCursor(j, 0);
		for(i = 0; i < 128; i++)
		{
			OLED_WriteData(0x00);
		}
	}
}
 
/**
  * @brief  OLED显示一个字符
  * @param  Line 行位置，范围：1~4
  * @param  Column 列位置，范围：1~16
  * @param  Char 要显示的一个字符，范围：ASCII可见字符
  * @retval 无
  */
void OLED_ShowChar(uint8_t Line, uint8_t Column, char Char)
{      	
	uint8_t i;
	OLED_SetCursor((Line - 1) * 2, (Column - 1) * 8);		//设置光标位置在上半部分
	for (i = 0; i < 8; i++)
	{
		OLED_WriteData(OLED_F8x16[Char - ' '][i]);			//显示上半部分内容
	}
	OLED_SetCursor((Line - 1) * 2 + 1, (Column - 1) * 8);	//设置光标位置在下半部分
	for (i = 0; i < 8; i++)
	{
		OLED_WriteData(OLED_F8x16[Char - ' '][i + 8]);		//显示下半部分内容
	}
}
 
/**
  * @brief  OLED显示字符串
  * @param  Line 起始行位置，范围：1~4
  * @param  Column 起始列位置，范围：1~16
  * @param  String 要显示的字符串，范围：ASCII可见字符
  * @retval 无
  */
void OLED_ShowString(uint8_t Line, uint8_t Column, char *String)
{
	uint8_t i;
	for (i = 0; String[i] != '\0'; i++)
	{
		OLED_ShowChar(Line, Column + i, String[i]);
	}
}
 
/**
  * @brief  OLED次方函数
  * @retval 返回值等于X的Y次方
  */
uint32_t OLED_Pow(uint32_t X, uint32_t Y)
{
	uint32_t Result = 1;
	while (Y--)
	{
		Result *= X;
	}
	return Result;
}
 
/**
  * @brief  OLED显示数字（十进制，正数）
  * @param  Line 起始行位置，范围：1~4
  * @param  Column 起始列位置，范围：1~16
  * @param  Number 要显示的数字，范围：0~4294967295
  * @param  Length 要显示数字的长度，范围：1~10
  * @retval 无
  */
void OLED_ShowNum(uint8_t Line, uint8_t Column, uint32_t Number, uint8_t Length)
{
	uint8_t i;
	for (i = 0; i < Length; i++)							
	{
		OLED_ShowChar(Line, Column + i, Number / OLED_Pow(10, Length - i - 1) % 10 + '0');
	}
}
 
/**
  * @brief  OLED显示数字（十进制，带符号数）
  * @param  Line 起始行位置，范围：1~4
  * @param  Column 起始列位置，范围：1~16
  * @param  Number 要显示的数字，范围：-2147483648~2147483647
  * @param  Length 要显示数字的长度，范围：1~10
  * @retval 无
  */
void OLED_ShowSignedNum(uint8_t Line, uint8_t Column, int32_t Number, uint8_t Length)
{
	uint8_t i;
	uint32_t Number1;
	if (Number >= 0)
	{
		OLED_ShowChar(Line, Column, '+');
		Number1 = Number;
	}
	else
	{
		OLED_ShowChar(Line, Column, '-');
		Number1 = -Number;
	}
	for (i = 0; i < Length; i++)							
	{
		OLED_ShowChar(Line, Column + i + 1, Number1 / OLED_Pow(10, Length - i - 1) % 10 + '0');
	}
}
 
/**
  * @brief  OLED显示数字（十六进制，正数）
  * @param  Line 起始行位置，范围：1~4
  * @param  Column 起始列位置，范围：1~16
  * @param  Number 要显示的数字，范围：0~0xFFFFFFFF
  * @param  Length 要显示数字的长度，范围：1~8
  * @retval 无
  */
void OLED_ShowHexNum(uint8_t Line, uint8_t Column, uint32_t Number, uint8_t Length)
{
	uint8_t i, SingleNumber;
	for (i = 0; i < Length; i++)							
	{
		SingleNumber = Number / OLED_Pow(16, Length - i - 1) % 16;
		if (SingleNumber < 10)
		{
			OLED_ShowChar(Line, Column + i, SingleNumber + '0');
		}
		else
		{
			OLED_ShowChar(Line, Column + i, SingleNumber - 10 + 'A');
		}
	}
}
 
/**
  * @brief  OLED显示数字（二进制，正数）
  * @param  Line 起始行位置，范围：1~4
  * @param  Column 起始列位置，范围：1~16
  * @param  Number 要显示的数字，范围：0~1111 1111 1111 1111
  * @param  Length 要显示数字的长度，范围：1~16
  * @retval 无
  */
void OLED_ShowBinNum(uint8_t Line, uint8_t Column, uint32_t Number, uint8_t Length)
{
	uint8_t i;
	for (i = 0; i < Length; i++)							
	{
		OLED_ShowChar(Line, Column + i, Number / OLED_Pow(2, Length - i - 1) % 2 + '0');
	}
}
 
/**
  * @brief  OLED初始化
  * @param  无
  * @retval 无
  */
void OLED_Init(void)
{
	HAL_Delay(100);
	
	OLED_WriteCommand(0xAE);	//关闭显示
	
	OLED_WriteCommand(0xD5);	//设置显示时钟分频比/振荡器频率
	OLED_WriteCommand(0x80);
	
	OLED_WriteCommand(0xA8);	//设置多路复用率
	OLED_WriteCommand(0x3F);
	
	OLED_WriteCommand(0xD3);	//设置显示偏移
	OLED_WriteCommand(0x00);
	
	OLED_WriteCommand(0x40);	//设置显示开始行
	
	OLED_WriteCommand(0xA1);	//设置左右方向，0xA1正常 0xA0左右反置
	
	OLED_WriteCommand(0xC8);	//设置上下方向，0xC8正常 0xC0上下反置
 
	OLED_WriteCommand(0xDA);	//设置COM引脚硬件配置
	OLED_WriteCommand(0x12);
	
	OLED_WriteCommand(0x81);	//设置对比度控制
	OLED_WriteCommand(0xCF);
 
	OLED_WriteCommand(0xD9);	//设置预充电周期
	OLED_WriteCommand(0xF1);
 
	OLED_WriteCommand(0xDB);	//设置VCOMH取消选择级别
	OLED_WriteCommand(0x30);
 
	OLED_WriteCommand(0xA4);	//设置整个显示打开/关闭
 
	OLED_WriteCommand(0xA6);	//设置正常/倒转显示
 
	OLED_WriteCommand(0x8D);	//设置充电泵
	OLED_WriteCommand(0x14);
 
	OLED_WriteCommand(0xAF);	//开启显示
		
	OLED_Clear();				//OLED清屏
}

六、最终测试程序

main.c中的删减版，只为了演示，大家不用删：


#include "main.h"
#include "i2c.h"
#include "gpio.h"
#include "OLED.h"
#include "Max30102.h"
void SystemClock_Config(void);
int main(void)
{
  int32_t HR_Value,BO_Value;
  int8_t HR_Valid,BO_Valid;
  HAL_Init();
  SystemClock_Config();
  MX_GPIO_Init();
  MX_I2C1_Init();
  MX_I2C2_Init();
  OLED_Init();
  OLED_ShowString(4,1,"jikli");
  Max30102_Init();
  Max30102_Safety();
  while (1)
  {
	Max30102_Calculate_HR_BO_Value(&HR_Value,&HR_Valid,&BO_Value,&BO_Valid);
	if(HR_Valid==1 && BO_Valid==1)
	{
		OLED_ShowString(1,1,"HR:");
		OLED_ShowString(2,1,"BO:");
		OLED_ShowNum(1,5,HR_Value,3);
		OLED_ShowNum(2,5,BO_Value,3);
	}
  }
}

最终实验效果：刚开始测得有点久而且数值不稳，要多测一会才能稳定。

七、algorithm代码补充

algorithm.c:


/** \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]; //red
 
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    
    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 Average
    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
    // flip wave form so that we can detect valley with peak detector
    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
    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
        *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 ratio is out of range
       *pch_spo2_valid  = 0; 
       return;
    }
    // 4 pt MA
    for(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 locations
    n_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]); //red
            n_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]); // ir
            n_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 value
            n_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*20)/n_denom ; //formular is ( n_y_ac *n_x_dc_max) / ( n_x_ac *n_y_dc_max) ;  ///*************************n_nume原来是*100************************//
                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 median
    else
        n_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 peaks
            n_width = 1;
            while (i+n_width < n_size && pn_x[i] == pn_x[i+n_width])    // find flat peaks
                n_width++;
            if (pn_x[i] > pn_x[i+n_width] && (*pn_npks) < 15 ){                            // find right edge of peaks
                pn_locs[(*pn_npks)++] = i;        
                // for flat peaks, peak location is left edge
                i += n_width+1;
            }
            else
                i += n_width;
        }
        else
            i++;
    }
}
 
 
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 -1
            if ( n_dist > n_min_distance || n_dist < -n_min_distance )
                pn_locs[(*pn_npks)++] = pn_locs[j];
        }
    }
 
    // Resort indices longo ascending order
    maxim_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;
    }
}

algorithm.h:


#ifndef ALGORITHM_H_
#define ALGORITHM_H_
 
#include "main.h"
 
#define true 1
#define false 0
#define FS 100
#define BUFFER_SIZE  (FS* 5) 
#define HR_FIFO_SIZE 7
#define MA4_SIZE  4 // DO NOT CHANGE
#define HAMMING_SIZE  5// DO NOT CHANGE
#define min(x,y) ((x) < (y) ? (x) : (y))
 
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);
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 );
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 );
void maxim_remove_close_peaks( int32_t *pn_locs, int32_t *pn_npks,   int32_t  *pn_x, int32_t n_min_distance );
void maxim_sort_ascend( int32_t *pn_x, int32_t n_size );
void maxim_sort_indices_descend(  int32_t  *pn_x, int32_t *pn_indx, int32_t n_size);
 
#endif /* ALGORITHM_H_ */

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