【开源】ESP8266_MAX30102_OLED屏幕实现血氧心率检测

本系列，是记录自己入门嵌入式领域的学习笔记。

看看能坚持多久。

今天是2023年5月2日

源代码的来源：https://github.com/yangqingyuan-byte/MAX30102-0.96_4pin_oled-esp8266_HR_and_SPO2

项目需求：

ESP8266_MAX30102_OLED屏幕实现血氧心率检测

硬件连接：

* ESP8266 --- OLED

* GND --- GND *

* 5V --- VCC 

* D1 --- SCL 

* D2 --- SDA 

* ESP8266 --- MAX30102

* 5V --- VIN

* G --- GND

* D0 --- INT

* D1 --- SCL

* D2 --- SDA

程序源码：

引入库

#include <U8g2lib.h>
#include <SPI.h>
#include <Wire.h>
#include "algorithm_by_RF.h"
#include "max30102.h"

这段代码引入了需要用到的库。其中 U8g2lib 是一个用于字体显示的库；SPI、Wire 分别是用于支持 SPI 和 I2C 协议的库；algorithm_by_RF 和 max30102 分别是根据最大值和最小值计算心率和血氧的自定义库。

// uncomment below line if cannot calculate readings
#define REVERSE_LED

这里定义了 REVERSE_LED 宏。如果无法计算读数，则应取消此行代码的注释。

OLED 屏幕初始化

U8G2_SSD1306_128X64_NONAME_F_SW_I2C u8g2(U8G2_R0, /* clock=*/ SCL, /* data=*/ SDA, /* reset=*/ U8X8_PIN_NONE);

定义了一个 U8G2_SSD1306_128X64_NONAME_F_SW_I2C 类型的对象 u8g2，这个对象代表了 OLED 屏幕，并把屏幕连接到 I2C 总线上。

void setup()
{pinMode(oxiInt, INPUT); // pin D0 connects to the interrupt output pin of the MAX30102u8g2.begin();u8g2.enableUTF8Print();u8g2.clearBuffer();delay(2000);u8g2.setFont(u8g2_font_unifont_tr);u8g2.setCursor(0, 14);u8g2.print("Initializing...");u8g2.sendBuffer();Wire.begin();Serial.begin(115200);Serial.println("Initializing");maxim_max30102_reset(); // resets the MAX30102maxim_max30102_read_reg(REG_INTR_STATUS_1, &uch_dummy); // Reads/clears the interrupt status registermaxim_max30102_init();                                  // initialize the MAX30102old_n_spo2 = 0.0;Serial.println(F("Time[s]\tSpO2\tHR\tRatio\tCorr"));timeStart = millis();
}

在 setup() 函数中，首先将 oxiInt 引脚设置为输入模式（用于连接到 MAX30102 的中断输出引脚），然后对 OLED 屏幕进行初始化操作，在开机画面上输出 "Initializing..."。接着使用 Wire 库初始化 I2C 总线，打开串口输出，并分别进行了 MAX30102 的复位、中断状态清除和初始化操作。最后输出表头 "Time[s]\tSpO2\tHR\tRatio\tCorr"，并记录开始时间。

显示心率和血氧值

void print_hr_spo2(int val_hr, int val_spo2){if(val_hr > 999 || val_hr < 0){return;}if(val_spo2 > 100 || val_spo2 < 0){return;}u8g2.clearBuffer();u8g2.setFont(u8g2_font_fub14_tr); u8g2.setCursor(0,14);u8g2.print(" HR");u8g2.setCursor(60,14);u8g2.print("SPO2");char str_hr[4];  u8g2.setFont(u8g2_font_fur20_tr);itoa(val_hr, str_hr, 10);if(val_hr > 99){u8g2.drawStr(0, 38, str_hr);}else if(val_hr > 9){u8g2.drawStr(14,38, str_hr);}else{u8g2.drawStr(28,38, str_hr);}char str_spo2[4];u8g2.setFont(u8g2_font_fur30_tr); itoa(val_spo2, str_spo2, 10);  if(val_spo2 > 99){u8g2.drawStr(55, 48, str_spo2);}else if(val_spo2 > 9){u8g2.drawStr(70, 48, str_spo2);}else{u8g2.drawStr(85, 48, str_spo2);    }u8g2.setFont(u8g2_font_fur11_tr); u8g2.setCursor(13,50);u8g2.print("bpm");u8g2.setCursor(110,64);u8g2.print("%");u8g2.sendBuffer();   
}

在 print_hr_spo2() 函数中，首先判断心率和血氧值是否在有效范围内（0~999 和 0~100），然后清空 OLED 屏幕缓存，并设置字体和显示位置。接着分别将心率和血氧值转化为字符串类型，并根据值的长度和位置绘制在屏幕上，最后输出单位并发送缓存。

void print_measuring(){u8g2.clearBuffer();u8g2.setFont(u8g2_font_fub14_tr); u8g2.setCursor(0,14);u8g2.print(" HR");u8g2.setCursor(60,14);u8g2.print("SPO2");char str_hr[4];  u8g2.setFont(u8g2_font_fur20_tr);u8g2.drawStr(10, 38, "---");char str_spo2[4];u8g2.setFont(u8g2_font_fur30_tr); u8g2.drawStr(65, 48, "---");u8g2.setFont(u8g2_font_unifont_tr);u8g2.setCursor(26,62);u8g2.print("Measuring...");    u8g2.sendBuffer();    
}

在 print_measuring() 函数中，清空 OLED 屏幕缓存，并设置字体和显示位置。接着绘制未测量状态的心率和血氧值，并输出 "Measuring..."，最后发送缓存。

void print_press(){u8g2.clearBuffer();u8g2.setFont(u8g2_font_fub14_tr); u8g2.setCursor(0,14);u8g2.print(" HR");u8g2.setCursor(60,14);u8g2.print("SPO2");char str_hr[4];  u8g2.setFont(u8g2_font_fur20_tr);u8g2.drawStr(10, 38, "---");char str_spo2[4];u8g2.setFont(u8g2_font_fur30_tr); u8g2.drawStr(65, 48, "---");u8g2.setFont(u8g2_font_unifont_tr);u8g2.setCursor(20,62);u8g2.print("Keep pressing");    u8g2.sendBuffer();    
}

在 print_press() 函数中，清空 OLED 屏幕缓存，并设置字体和显示位置。接着绘制要求将指尖放到传感器上。

完整代码如下：

#include <U8g2lib.h>
#include <SPI.h>
#include <Wire.h>
#include "algorithm_by_RF.h"
#include "max30102.h"
#define REVERSE_LEDU8G2_SSD1306_128X64_NONAME_F_SW_I2C u8g2(U8G2_R0, /* clock=*/ SCL, /* data=*/ SDA, /* reset=*/ U8X8_PIN_NONE);const byte oxiInt = 16; // pin connected to MAX30102 INTuint32_t elapsedTime, timeStart;uint32_t aun_ir, aun_red;
uint32_t aun_ir_buffer[BUFFER_SIZE];  // infrared LED sensor data
uint32_t aun_red_buffer[BUFFER_SIZE]; // red LED sensor data
float old_n_spo2;                     // Previous SPO2 value
uint8_t uch_dummy;
bool showMeasuring = false;void setup()
{pinMode(oxiInt, INPUT); // pin D0 connects to the interrupt output pin of the MAX30102u8g2.begin();u8g2.enableUTF8Print();u8g2.clearBuffer();delay(2000);u8g2.setFont(u8g2_font_unifont_tr);u8g2.setCursor(0, 14);u8g2.print("Initializing...");u8g2.sendBuffer();Wire.begin();Serial.begin(115200);Serial.println("Initializing");maxim_max30102_reset(); // resets the MAX30102maxim_max30102_read_reg(REG_INTR_STATUS_1, &uch_dummy); // Reads/clears the interrupt status registermaxim_max30102_init();                                  // initialize the MAX30102old_n_spo2 = 0.0;Serial.println(F("Time[s]\tSpO2\tHR\tRatio\tCorr"));timeStart = millis();
}void print_hr_spo2(int val_hr, int val_spo2){if(val_hr > 999 || val_hr < 0){return;}if(val_spo2 > 100 || val_spo2 < 0){return;}u8g2.clearBuffer();u8g2.setFont(u8g2_font_fub14_tr); u8g2.setCursor(0,14);u8g2.print(" HR");u8g2.setCursor(60,14);u8g2.print("SPO2");char str_hr[4];  u8g2.setFont(u8g2_font_fur20_tr);itoa(val_hr, str_hr, 10);if(val_hr > 99){u8g2.drawStr(0, 38, str_hr);}else if(val_hr > 9){u8g2.drawStr(14,38, str_hr);}else{u8g2.drawStr(28,38, str_hr);}char str_spo2[4];u8g2.setFont(u8g2_font_fur30_tr); itoa(val_spo2, str_spo2, 10);  if(val_spo2 > 99){u8g2.drawStr(55, 48, str_spo2);}else if(val_spo2 > 9){u8g2.drawStr(70, 48, str_spo2);}else{u8g2.drawStr(85, 48, str_spo2);    }u8g2.setFont(u8g2_font_fur11_tr); u8g2.setCursor(13,50);u8g2.print("bpm");u8g2.setCursor(110,64);u8g2.print("%");u8g2.sendBuffer();   
}void print_measuring(){u8g2.clearBuffer();u8g2.setFont(u8g2_font_fub14_tr); u8g2.setCursor(0,14);u8g2.print(" HR");u8g2.setCursor(60,14);u8g2.print("SPO2");char str_hr[4];  u8g2.setFont(u8g2_font_fur20_tr);u8g2.drawStr(10, 38, "---");char str_spo2[4];u8g2.setFont(u8g2_font_fur30_tr); u8g2.drawStr(65, 48, "---");u8g2.setFont(u8g2_font_unifont_tr);u8g2.setCursor(26,62);u8g2.print("Measuring...");    u8g2.sendBuffer();    
}void print_press(){u8g2.clearBuffer();u8g2.setFont(u8g2_font_fub14_tr); u8g2.setCursor(0,14);u8g2.print(" HR");u8g2.setCursor(60,14);u8g2.print("SPO2");char str_hr[4];  u8g2.setFont(u8g2_font_fur20_tr);u8g2.drawStr(10, 38, "---");char str_spo2[4];u8g2.setFont(u8g2_font_fur30_tr); u8g2.drawStr(65, 48, "---");u8g2.setFont(u8g2_font_unifont_tr);u8g2.setCursor(20,62);u8g2.print("Keep pressing");    u8g2.sendBuffer();    
}void loop()
{// Serial.println("looping");float n_spo2, ratio, correl; // SPO2 valueint8_t ch_spo2_valid;        // indicator to show if the SPO2 calculation is validint32_t n_heartrate;         // heart rate valueint8_t ch_hr_valid;          // indicator to show if the heart rate calculation is validint32_t i;// buffer length of BUFFER_SIZE stores ST seconds of samples running at FS sps// read BUFFER_SIZE samples, and determine the signal rangefor (i = 0; i < BUFFER_SIZE; i++){while (digitalRead(oxiInt) == 1); // wait until the interrupt pin assertsdelay(1);// wdt_reset();
#ifdef REVERSE_LEDmaxim_max30102_read_fifo(&aun_ir, &aun_red); // read from MAX30102 FIFO
#elsemaxim_max30102_read_fifo(&aun_red, &aun_ir); // read from MAX30102 FIFO
#endifif (aun_ir < 5000){break;}if (i == 0){if(showMeasuring){print_measuring();showMeasuring = false;}Serial.print("Measuring...");}*(aun_ir_buffer + i) = aun_ir;*(aun_red_buffer + i) = aun_red;}if (aun_ir < 5000){print_press();showMeasuring = true;Serial.print("Put On Finger");}else{// calculate heart rate and SpO2 after BUFFER_SIZE samples (ST seconds of samples) using Robert's methodrf_heart_rate_and_oxygen_saturation(aun_ir_buffer, BUFFER_SIZE, aun_red_buffer, &n_spo2, &ch_spo2_valid, &n_heartrate, &ch_hr_valid, &ratio, &correl);// Serial.println("rf_heart_rate_and_oxygen_saturation");elapsedTime = millis() - timeStart;elapsedTime /= 1000; // Time in secondsif (ch_hr_valid && ch_spo2_valid){Serial.print(elapsedTime);Serial.print("\t");Serial.print(n_spo2);Serial.print("\t");Serial.print(n_heartrate, DEC);Serial.print("\t");Serial.print(ratio);Serial.print("\t");Serial.print(correl);Serial.println("");print_hr_spo2(n_heartrate, (int)(n_spo2+0.5));old_n_spo2 = n_spo2;}}
}