Pulse Oximeter

#define BUZZER 10
#define BUTTONDURATION 6
#define BUTTONSOUND 7

#include <Wire.h>
#include "MAX30105.h"
#include <PeakDetection.h>

MAX30105 particleSensor;

#include <SPI.h>
#include <Adafruit_GFX.h>
#include <Adafruit_SSD1306.h>

#define SCREEN_WIDTH 128 // OLED display width, in pixels
#define SCREEN_HEIGHT 64 // OLED display height, in pixels

// Declaration for an SSD1306 display connected to I2C (SDA, SCL pins)
#define OLED_RESET     4 // Reset pin # (or -1 if sharing Arduino reset pin)
Adafruit_SSD1306 display(SCREEN_WIDTH, SCREEN_HEIGHT, &Wire, OLED_RESET);

PeakDetection peakDetection;
double starttime;

void setup()
{
  Serial.begin(115200); //Initialize serial monitor/plotter

  // Initialize button and buzzer pins
  pinMode(BUZZER, OUTPUT);
  pinMode(BUTTONDURATION, INPUT);
  pinMode(BUTTONSOUND, INPUT);

  // Initialize sensor
  if (!particleSensor.begin(Wire, 200)) //Use default I2C port, 400kHz speed
  {
    //Serial.println("MAX30105 was not found. Please check wiring/power. ");
    while (1);
  }

  //Setup to sense a nice looking saw tooth on the plotter
  byte ledBrightness = 0x1F; //Options: 0=Off to 255=50mA 1F=31
  byte sampleAverage = 8; //Options: 1, 2, 4, 8, 16, 32
  byte ledMode = 3; //Options: 1 = Red only, 2 = Red + IR, 3 = Red + IR + Green
  int sampleRate = 100; //Options: 50, 100, 200, 400, 800, 1000, 1600, 3200
  int pulseWidth = 411; //Options: 69, 118, 215, 411
  int adcRange = 4096; //Options: 2048, 4096, 8192, 16384

  particleSensor.setup(ledBrightness, sampleAverage, ledMode, sampleRate, pulseWidth, adcRange);

  //Set up OLED
  display.begin(SSD1306_SWITCHCAPVCC, 0x3C);
  display.setTextSize(1);
  display.setTextColor(WHITE,BLACK);
  display.clearDisplay();
  display.setCursor(0,24);

  peakDetection.begin(10, 1, 0.6); //Peak Detection presets: lag=32, threshold=2, influence=0.5
}

int count = 0;
double firsttime = 0;
double lasttime = 0;
bool BPMbelow = true;
int bpm1 = 0;
double redarray[100];
double irarray[100];
double peakarray[100];
int maximumred = 0;
int minimumred = 150000;
int maximumir = 0;
int minimumir = 150000;
float acquisitionduration = 10;
float difference = 0;
int k = 0;
double R = 0;

void loop()
{
  //Collect infrared and red light data, use peak detection on ir data
  double ir = particleSensor.getIR();
  double red = particleSensor.getRed();
  peakDetection.add(ir);
  double peak = peakDetection.getPeak();
  double peakprint = 1000 * peak + 120000;

  /*
  //Plots IR and red data as well as peaks
  Serial.print(ir); //Send raw data to plotter
  Serial.print(","); //Send raw data to plotter
  Serial.print(red); //Send raw data to plotter
  Serial.print(",");
  Serial.println(peakprint);
*/
////////////////////////////////////////////////////////////////////////////////////////////

  //Change acquisition duration to 5 seconds if button pressed
  if (digitalRead(BUTTONDURATION) == HIGH){
    acquisitionduration = 5;
  }

  else if (digitalRead(BUTTONDURATION) == LOW){
    acquisitionduration = 10;
  }

  //Measure Heart Rate
  if (peak > 0 && BPMbelow) //If detects peak, and there was not a peak before
  {
    BPMbelow = false; //Peak is occuring, measurement is not below threshold
    if (count == 0) //Takes time at first data point
    {
      firsttime = millis();
    }
  }

  if (peak <= 0 && !BPMbelow)
  {
    BPMbelow = true; //Peak is not occuring, measurement is below threshold
    count++; //Counts at the end of each beat
    lasttime = millis(); //Takes time at end of peak
    difference = (lasttime - firsttime) / 1000;
    if (digitalRead(BUTTONSOUND) == HIGH){
      tone(BUZZER,60,100); //If button pressed, piezo buzzer makes sound at every beat
    }
    //particleSensor.nextSample(); //Moves to next sample
  }

////////////////////////////////////////////////////////////////////////////////////////////

  redarray[k] = red; //Create array for red light values
  irarray[k] = ir; //Create array for IR light values

  //Measure modulation ratio R
  if (redarray[k] > maximumred){
    maximumred = redarray[k]; //Sets maximum of red
  }
  if (irarray[k] > maximumir){
    maximumir = irarray[k]; //Sets maximum of ir
  }
  if (redarray[k] < minimumred){
    minimumred = redarray[k]; //Sets minimum or red
  }
  if (irarray[k] <details minimumir){
    minimumir = irarray[k]; //Sets minimum of ir
  }

  if (k <div 99){
    k++;
  }
  else if (k == 99){ //Iterates through 100 samples, then resets
    k = 0;
    maximumred = 0;
    minimumred = 150000;
    maximumir = 0;
    minimumir = 150000;
  }

////////////////////////////////////////////////////////////////////////////////////////////

  if (difference >= acquisitionduration){ //Once time has reached acquisition duration
    bpm1 = count * 60 / difference; //Calculates bpm
    count = 0; //Resets count of beats to zero
    double redAC = maximumred - minimumred;
    double redDC = (minimumred+maximumred)/2;
    double redmeasure = redAC/redDC;
    double irAC = maximumir - minimumir;
    double irDC = (minimumir+maximumir)/2;
    double irmeasure = irAC/irDC;
    R = fabs(redmeasure/irmeasure); //Calculates modulation ratio
    difference = 0; //Resets time to zero
  }

////////////////////////////////////////////////////////////////////////////////////////////
  //Display values on OLED
  display.setCursor(0,24);
  display.clearDisplay();
  display.print("Pulse: ");
  display.print(bpm1); //Display current pulse on OLED in BPM
  display.setCursor(0,34);
  display.print("R: ");
  display.print(R); //Display current R for oxygen saturation
  display.display();
}