ESP32 Vital Signs Monitor

#include <Arduino.h>
#include <Wire.h>
#include <SPI.h>
#include <SD.h>
#include <Adafruit_GFX.h>
#include <Adafruit_SSD1306.h>
#include <Adafruit_MLX90614.h>
#include <Adafruit_ADS1X15.h>
#include <RTClib.h>
#include <MAX30105.h>
#include <spo2_algorithm.h>
#include <math.h>

// BENCH PROTOTYPE ONLY. AD8232 connects only to a purpose-built ECG simulator.
Adafruit_SSD1306 screen(128,64,&Wire,-1);
Adafruit_MLX90614 thermometer;
Adafruit_ADS1115 adc;
RTC_DS3231 rtc;
MAX30105 pulse;
File logFile;
bool oledOK, tempOK, adcOK, rtcOK, pulseOK, sdOK;
bool simulated=false, rtcValid=false;
uint32_t ir[100],red[100],lastIR=0,lastRed=0;
int fill=0;
int32_t oxygen=0,heart=0;
int8_t oxygenValid=0,heartValid=0;
float objectC=NAN,ambientC=NAN,ecgV=NAN;
int leadOff=1;
uint32_t lastECG=0,lastSlow=0,lastFlush=0,lastOptical=0;
String previousDisplay;

void openLog() {
  if(logFile) {logFile.flush(); logFile.close();}
  sdOK=false;
  for(int i=0;i<1000;i++) {
    char path[24]; snprintf(path,sizeof(path),"/%c%03d.csv",simulated?'S':'R',i);
    if(SD.exists(path)) continue;
    logFile=SD.open(path,FILE_WRITE);
    if(logFile) {
      sdOK=true;
      logFile.println("mode,ms,unix_time,rtc_valid,ecg_output_V,lead_off,red_raw,ir_raw,heart_bpm,spo2_percent,object_C,ambient_C");
      Serial.print("Logging: ");Serial.println(path);
    }
    break;
  }
}
void setMode(bool sim) {
  simulated=sim; fill=0; heartValid=oxygenValid=0;
  heart=oxygen=0;lastIR=lastRed=0;ecgV=objectC=ambientC=NAN;
  previousDisplay="";
  if(sdOK) openLog();
  Serial.println(sim?"SIMULATED DATA MODE":"REAL SENSOR MODE: ECG SIMULATOR ONLY");
}
void setup() {
  Serial.begin(115200);
  pinMode(32,INPUT);pinMode(33,INPUT);
  Wire.begin(21,22);Wire.setClock(100000);Wire.setTimeOut(50);
  Wire.beginTransmission(0x3C);
  oledOK=Wire.endTransmission()==0 && screen.begin(SSD1306_SWITCHCAPVCC,0x3C);
  if(oledOK) {screen.setTextSize(1);screen.setTextColor(SSD1306_WHITE);}
  tempOK=thermometer.begin();
  rtcOK=rtc.begin();
  rtcValid=rtcOK && !rtc.lostPower();
  // Do not invent a date. Set clock explicitly using T followed by Unix seconds.
  adcOK=adc.begin(0x48);
  if(adcOK) {adc.setGain(GAIN_ONE);adc.setDataRate(RATE_ADS1115_860SPS);}
  pulseOK=pulse.begin(Wire,100000);
  if(pulseOK) pulse.setup(0x1F,4,2,100,411,4096); // 100 / 4 = 25 optical samples/s
  SPI.begin(18,19,23,4);
  sdOK=SD.begin(4,SPI,4000000);
  if(sdOK) openLog();
  Serial.printf("OLED=%d MAX30102=%d MLX90614=%d ADS1115=%d RTC=%d RTC_VALID=%d SD=%d\n",oledOK,pulseOK,tempOK,adcOK,rtcOK,rtcValid,sdOK);
  Serial.println("s: simulated data; r: real sensors; f: flush SD. T<Unix seconds> sets RTC.");
  Serial.println("No electrodes on a person. Values are not medical measurements.");
}
void loop() {
  static String command;
  while(Serial.available()) {
    char c=Serial.read();
    if(c=='\n'||c=='\r') {
      if(command=="s")setMode(true);
      else if(command=="r")setMode(false);
      else if(command=="f" && logFile)logFile.flush();
      else if(command.startsWith("T")&&rtcOK) {
        uint32_t t=strtoul(command.c_str()+1,nullptr,10);
        if(t>=1704067200UL && t<4102444800UL) {rtc.adjust(DateTime(t));rtcValid=true;}
      }
      command="";
    } else if(command.length()<32) command+=c;
  }
  uint32_t now=millis();
  if(pulseOK) {
    pulse.check();
    while(pulse.available()) {
      uint32_t i=pulse.getFIFOIR(),r=pulse.getFIFORed();pulse.nextSample();
      if(simulated)continue;
      lastOptical=now;lastIR=i;lastRed=r;
      if(i<50000) {fill=0;heartValid=oxygenValid=0;continue;}
      ir[fill]=i;red[fill]=r;fill++;
      if(fill==100) {
        maxim_heart_rate_and_oxygen_saturation(ir,100,red,&oxygen,&oxygenValid,&heart,&heartValid);
        if(heart<30||heart>220)heartValid=0;
        if(oxygen<0||oxygen>100)oxygenValid=0;
        memmove(ir,ir+25,75*sizeof(uint32_t));memmove(red,red+25,75*sizeof(uint32_t));fill=75;
      }
    }
  }
  if(!simulated && now-lastOptical>2000) {heartValid=oxygenValid=0;lastIR=lastRed=0;fill=0;}
  // Best-effort 100 Hz ECG-output recording, not diagnostic ECG timing.
  if(now-lastECG>=10) {
    lastECG=now;
    if(simulated) {
      float p=(now%833)/833.0f;
      ecgV=1.65f+0.5f*expf(-powf((p-.4f)/.015f,2))+.05f*sinf(p*6.283185f);
      leadOff=0;heart=72;oxygen=98;heartValid=oxygenValid=1;
      lastIR=90000+(int)(1000*sinf(p*6.283185f));lastRed=80000+(int)(800*sinf(p*6.283185f));
    } else {
      leadOff=digitalRead(32)||digitalRead(33);
      ecgV=adcOK?adc.computeVolts(adc.readADC_SingleEnded(0)):NAN;
    }
    if(sdOK && logFile) {
      char row[220];
      unsigned long epoch=rtcValid?rtc.now().unixtime():0;
      snprintf(row,sizeof(row),"%s,%lu,%lu,%d,%.5f,%d,%lu,%lu,%ld,%ld,%.2f,%.2f\n",simulated?"SIM":"REAL",(unsigned long)now,epoch,rtcValid,ecgV,leadOff,(unsigned long)lastRed,(unsigned long)lastIR,(long)(heartValid?heart:-1),(long)(oxygenValid?oxygen:-1),objectC,ambientC);
      if(logFile.print(row)==0) {sdOK=false;Serial.println("SD write failed");}
    }
  }
  if(now-lastSlow>=1000) {
    lastSlow=now;
    objectC=simulated?36.7f:(tempOK?thermometer.readObjectTempC():NAN);
    ambientC=simulated?24.0f:(tempOK?thermometer.readAmbientTempC():NAN);
    String text=simulated?"SIMULATION ONLY\n":"BENCH / NOT MEDICAL\n";
    text+="HR:"+String(heartValid?String(heart):"--")+" O2:"+String(oxygenValid?String(oxygen):"--")+"%\n";
    text+="Surface:"+String(objectC,1)+"C\n";
    text+="ECG:"+String(ecgV,3)+"V L:"+String(leadOff)+"\n";
    text+="SD:"+String(sdOK?"REC":"FAIL")+" RTC:"+String(rtcValid?"OK":"UNSET")+"\n";
    text+="s=sim r=real (USB)";
    Serial.println(text);
    if(oledOK && text!=previousDisplay) {screen.clearDisplay();screen.setCursor(0,0);screen.print(text);screen.display();previousDisplay=text;}
  }
  if(now-lastFlush>=2000) {lastFlush=now;if(logFile)logFile.flush();}
  delay(1);
}