STM32驱动MAX30102心率血氧传感器（OLED显示）

简介

MAX30102是一个集成的脉搏血氧仪和心率监测仪模块。它包括内部led，光电探测器，光学元件，和低噪声电子与环境光排斥。MAX30102提供了一个完整的系统解决方案，以简化移动和可穿戴设备的设计过程。MAX30102运行在一个1.8V电源和一个单独的3.3V电源上。通信是通过一个标准的i2c兼容的接口。该模块可以通过零备用电流的软件关闭，允许电源轨道始终保持供电。

电气参数

系统框图

MAX30102是一个完整的脉搏血氧仪和心率传感器系统解决方案模块，为可穿戴设备的苛刻要求而设计。该设备保持了一个非常小的解决方案尺寸，而不牺牲光学或电气性能。集成到可穿戴系统中需要最小的外部硬件组件。MAX30102可以通过软件寄存器进行完全可调，并且数字输出数据可以存储在IC内的一个32深的FIFO中。FIFO允许MAX30102连接到共享总线上的微控制器或处理器，在其中，数据不会从MAX30102的寄存器中连续读取。MAX30102有一个片上的温度传感器，用于校准SpO2子系统的温度依赖性。该温度传感器的固有分辨率0.0625°C。器件输出数据对红外LED的波长相对不敏感，其中红色LED的波长对正确解释数据至关重要。与MAX30102输出信号一起使用的SpO2算法可以补偿环境温度变化时的相关SpO2误差。

接线

代码

 #include "led.h"
#include "delay.h"
#include "sys.h"
#include "usart.h"
#include "max30102.h" 
#include "myiic.h"
#include "algorithm.h"
#include "oled.h"

uint32_t aun_ir_buffer[500]; //IR LED sensor data
int32_t n_ir_buffer_length;    //data length
uint32_t aun_red_buffer[500];    //Red LED sensor data
int32_t n_sp02; //SPO2 value
int8_t ch_spo2_valid;   //indicator to show if the SP02 calculation is valid
int32_t n_heart_rate;   //heart rate value
int8_t  ch_hr_valid;    //indicator to show if the heart rate calculation is valid
uint8_t uch_dummy;

#define MAX_BRIGHTNESS 255

void dis_DrawCurve(u32* data,u8 x);

int main(void)
{ 
	//variables to calculate the on-board LED brightness that reflects the heartbeats
	uint32_t un_min, un_max, un_prev_data;  
	int i;
	int32_t n_brightness;
	float f_temp;
	u8 temp_num=0;
	u8 temp[6];
	u8 str[100];
	u8 dis_hr=0,dis_spo2=0;

	NVIC_Configuration();
	delay_init();	    	 //延时函数初始化	  
	uart_init(115200);	 	//串口初始化为115200
	LED_Init();
	
	//OLED
	OLED_Init();
	OLED_ShowString(0,0,"  initializing  ",16);
	OLED_Refresh_Gram();//更新显示到OLED	 

	max30102_init();

	printf("\r\n MAX30102  init  \r\n");

	un_min=0x3FFFF;
	un_max=0;
	
	n_ir_buffer_length=500; //buffer length of 100 stores 5 seconds of samples running at 100sps
	//read the first 500 samples, and determine the signal range
    for(i=0;i<n_ir_buffer_length;i++)
    {
        while(MAX30102_INT==1);   //wait until the interrupt pin asserts
        
		max30102_FIFO_ReadBytes(REG_FIFO_DATA,temp);
		aun_red_buffer[i] =  (long)((long)((long)temp[0]&0x03)<<16) | (long)temp[1]<<8 | (long)temp[2];    // Combine values to get the actual number
		aun_ir_buffer[i] = (long)((long)((long)temp[3] & 0x03)<<16) |(long)temp[4]<<8 | (long)temp[5];   // Combine values to get the actual number
            
        if(un_min>aun_red_buffer[i])
            un_min=aun_red_buffer[i];    //update signal min
        if(un_max<aun_red_buffer[i])
            un_max=aun_red_buffer[i];    //update signal max
    }
	un_prev_data=aun_red_buffer[i];
	//calculate heart rate and SpO2 after first 500 samples (first 5 seconds of samples)
    maxim_heart_rate_and_oxygen_saturation(aun_ir_buffer, n_ir_buffer_length, aun_red_buffer, &n_sp02, &ch_spo2_valid, &n_heart_rate, &ch_hr_valid); 
	
	while(1)
	{
		i=0;
        un_min=0x3FFFF;
        un_max=0;
		
		//dumping the first 100 sets of samples in the memory and shift the last 400 sets of samples to the top
        for(i=100;i<500;i++)
        {
            aun_red_buffer[i-100]=aun_red_buffer[i];
            aun_ir_buffer[i-100]=aun_ir_buffer[i];
            
            //update the signal min and max
            if(un_min>aun_red_buffer[i])
            un_min=aun_red_buffer[i];
            if(un_max<aun_red_buffer[i])
            un_max=aun_red_buffer[i];
        }
		//take 100 sets of samples before calculating the heart rate.
        for(i=400;i<500;i++)
        {
            un_prev_data=aun_red_buffer[i-1];
            while(MAX30102_INT==1);
            max30102_FIFO_ReadBytes(REG_FIFO_DATA,temp);
			aun_red_buffer[i] =  (long)((long)((long)temp[0]&0x03)<<16) | (long)temp[1]<<8 | (long)temp[2];    // Combine values to get the actual number
			aun_ir_buffer[i] = (long)((long)((long)temp[3] & 0x03)<<16) |(long)temp[4]<<8 | (long)temp[5];   // Combine values to get the actual number
        
            if(aun_red_buffer[i]>un_prev_data)
            {
                f_temp=aun_red_buffer[i]-un_prev_data;
                f_temp/=(un_max-un_min);
                f_temp*=MAX_BRIGHTNESS;
                n_brightness-=(int)f_temp;
                if(n_brightness<0)
                    n_brightness=0;
            }
            else
            {
                f_temp=un_prev_data-aun_red_buffer[i];
                f_temp/=(un_max-un_min);
                f_temp*=MAX_BRIGHTNESS;
                n_brightness+=(int)f_temp;
                if(n_brightness>MAX_BRIGHTNESS)
                    n_brightness=MAX_BRIGHTNESS;
            }
			//send samples and calculation result to terminal program through UART
			if(ch_hr_valid == 1 && n_heart_rate<120)//**/ ch_hr_valid == 1 && ch_spo2_valid ==1 && n_heart_rate<120 && n_sp02<101
			{
				dis_hr = n_heart_rate;
				dis_spo2 = n_sp02;
			}
			else
			{
				dis_hr = 0;
				dis_spo2 = 0;
			}
				printf("HR=%i, ", n_heart_rate); 
				printf("HRvalid=%i, ", ch_hr_valid);
				printf("SpO2=%i, ", n_sp02);
				printf("SPO2Valid=%i\r\n", ch_spo2_valid);
		}
        maxim_heart_rate_and_oxygen_saturation(aun_ir_buffer, n_ir_buffer_length, aun_red_buffer, &n_sp02, &ch_spo2_valid, &n_heart_rate, &ch_hr_valid);
		
		//显示刷新
		LED0=0;
		if(dis_hr == 0 && dis_spo2 == 0)  //**dis_hr == 0 && dis_spo2 == 0
		{
			sprintf((char *)str,"HR:--- SpO2:--- ");//**HR:--- SpO2:--- 
		}
		else{
			sprintf((char *)str,"HR:%3d SpO2:%3d ",dis_hr,dis_spo2);//**HR:%3d SpO2:%3d 
		}
		OLED_ShowString(0,0,str,16);
		OLED_Fill(0,23,127,63,0);
		//红光在上，红外在下
		dis_DrawCurve(aun_red_buffer,20);
		dis_DrawCurve(aun_ir_buffer,0);
		OLED_Refresh_Gram();//更新显示到OLED	 
	}
}

void dis_DrawCurve(u32* data,u8 x)
{
	u16 i;
	u32 max=0,min=262144;
	u32 temp;
	u32 compress;
	
	for(i=0;i<128*2;i++)
	{
		if(data[i]>max)
		{
			max = data[i];
		}
		if(data[i]<min)
		{
			min = data[i];
		}
	}
	
	compress = (max-min)/20;
	
	for(i=0;i<128;i++)
	{
		temp = data[i*2] + data[i*2+1];
		temp/=2;
		temp -= min;
		temp/=compress;
		if(temp>20)temp=20;
		OLED_DrawPoint(i,63-x-temp,1);
	}
} 
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结果

总结

手指放置红色LED上，OLED上会显示心率、血氧值，并且还有波形显示，刚开始数值和波形会有些波动，静置几秒后，数值和波形方可稳定。