Pulse Oximeter

1// max30102 libraries
2#include <Wire.h>
3#include "MAX30105.h"
4#include "spo2_algorithm.h"
5
6// oled libraries
7#include <SSD1306Ascii.h>
8#include <SSD1306AsciiWire.h>
9
10MAX30105 particleSensor;
11SSD1306AsciiWire oled;
12
13#define MAX_BRIGHTNESS 255
14
15uint16_t irBuffer[100]; //infrared LED sensor data
16uint16_t redBuffer[100];  //red LED sensor data
17
18int32_t bufferLength; //data length
19int32_t spo2; //SPO2 value
20int8_t validSPO2; //indicator to show if the SPO2 calculation is valid
21int32_t heartRate; //heart rate value
22int8_t validHeartRate; //indicator to show if the heart rate calculation is valid
23
24byte pulseLED = 11; //Must be on PWM pin
25byte readLED = 13; //Blinks with each data read
26
27int prevPulse = 0;
28int prevO2 = 0;
29
30void setup()
31{
32  Serial.begin(115200); // initialize serial communication at 115200 bits per second:
33  Wire.begin();
34  
35  // set-up for the oled
36  oled.begin(&Adafruit128x32, 0x3C);
37  oled.setFont(Verdana12);
38  oled.clear();
39  oled.setCursor(0, 0);
40
41  pinMode(pulseLED, OUTPUT);
42  pinMode(readLED, OUTPUT);
43 
44  // Initialize sensor
45  if (!particleSensor.begin(Wire, I2C_SPEED_FAST)) //Use default I2C port, 400kHz speed
46  {
47    Serial.println(F("MAX30105 was not found. Please check wiring/power."));
48    while (1);
49  }
50 
51  Serial.println(F("Attach sensor to finger with rubber band. Press any key to start conversion"));
52  oled.println("Place finger on");
53  oled.println("sensor");
54  while (Serial.available() == 0) ; //wait until user presses a key
55  Serial.read();
56  
57  byte ledBrightness = 60; //Options: 0=Off to 255=50mA
58  byte sampleAverage = 4; //Options: 1, 2, 4, 8, 16, 32
59  byte ledMode = 2; //Options: 1 = Red only, 2 = Red + IR, 3 = Red + IR + Green
60  byte sampleRate = 100; //Options: 50, 100, 200, 400, 800, 1000, 1600, 3200
61  int pulseWidth = 411; //Options: 69, 118, 215, 411
62  int adcRange = 4096; //Options: 2048, 4096, 8192, 16384
63  
64  particleSensor.setup(ledBrightness, sampleAverage, ledMode, sampleRate, pulseWidth, adcRange); //Configure sensor with these settings
65}
66
67void loop()
68{
69  bufferLength = 100; //buffer length of 100 stores 4 seconds of samples running at 25sps
70
71  //read the first 100 samples, and determine the signal range
72  for (byte i = 0 ; i < bufferLength ; i++)
73  {
74    while (particleSensor.available() == false) //do we have new data?
75      particleSensor.check(); //Check the sensor for new data
76      
77    redBuffer[i] = particleSensor.getRed();
78    irBuffer[i] = particleSensor.getIR();
79    particleSensor.nextSample(); //We're finished with this sample so move to next sample
80
81    Serial.print(F("red="));
82    Serial.print(redBuffer[i], DEC);
83    Serial.print(F(", ir="));
84    Serial.println(irBuffer[i], DEC);
85  }
86
87  //calculate heart rate and SpO2 after first 100 samples (first 4 seconds of samples)
88  maxim_heart_rate_and_oxygen_saturation(irBuffer, bufferLength, redBuffer, &spo2, &validSPO2, &heartRate, &validHeartRate);
89
90  //Continuously taking samples from MAX30102.  Heart rate and SpO2 are calculated every 1 second
91  while (1)
92  {
93    //dumping the first 25 sets of samples in the memory and shift the last 75 sets of samples to the top
94    for (byte i = 25; i < 100; i++)
95    {
96      redBuffer[i - 25] = redBuffer[i];
97      irBuffer[i - 25] = irBuffer[i];
98    }
99
100    //take 25 sets of samples before calculating the heart rate.
101    for (byte i = 75; i < 100; i++)
102    {
103      while (particleSensor.available() == false) //do we have new data?
104        particleSensor.check(); //Check the sensor for new data
105
106      digitalWrite(readLED, !digitalRead(readLED)); //Blink onboard LED with every data read
107
108      redBuffer[i] = particleSensor.getRed();
109      irBuffer[i] = particleSensor.getIR();
110      particleSensor.nextSample(); //We're finished with this sample so move to next sample
111     
112      //send samples and calculation result to terminal program through UART
113     
114      Serial.print(F("red="));
115      Serial.print(redBuffer[i], DEC);
116      Serial.print(F(", ir="));
117      Serial.print(irBuffer[i], DEC);
118
119      Serial.print(F(", HRvalid="));
120      Serial.print(validHeartRate, DEC);
121     
122      Serial.print(F(", SPO2Valid="));
123      Serial.println(validSPO2, DEC);
124
125      int HR = validSPO2;
126      Serial.println(HR);
127      
128      if (validSPO2 == 1 && (prevPulse != heartRate || prevO2 != spo2)) {
129          oled.clear();
130   
131          oled.setCursor(0, 0);
132          oled.print("HR: ");
133          oled.println(heartRate, DEC);
134
135
136          oled.print("SPO2: ");
137          oled.print(spo2, DEC);
138      }
139
140      prevO2 = spo2;
141      prevPulse = heartRate;
142    }
143
144    maxim_heart_rate_and_oxygen_saturation(irBuffer, bufferLength, redBuffer, &spo2, &validSPO2, &heartRate, &validHeartRate);
145  }
146}