File content as of revision 14:23390a020d1c:

#include "Heart.h"
#include "mbed.h"

volatile int rate[10];                    // array to hold last ten IBI values
volatile unsigned long sampleCounter = 0;          // used to determine pulse timing
volatile unsigned long lastBeatTime = 0;           // used to find IBI
volatile int P =512;                      // used to find peak in pulse wave, seeded
volatile int T = 512;                     // used to find trough in pulse wave, seeded
volatile int thresh = 512;                // used to find instant moment of heart beat, seeded
volatile int amp = 100;                   // used to hold amplitude of pulse waveform, seeded
volatile bool firstBeat = true;        // used to seed rate array so we startup with reasonable BPM
volatile bool secondBeat = false;      // used to seed rate array so we startup with reasonable BPM
volatile int BPM;                   // used to hold the pulse rate
volatile int Signal;                // holds the incoming raw data
volatile int IBI = 600;             // holds the time between beats, must be seeded! 
volatile bool Pulse = false;     // true when pulse wave is high, false when it's low
volatile bool QS = false;        // becomes true when Arduoino finds a beat.
volatile bool isBeating = false;
volatile int beatCount = 0;
volatile int PulseLength = 0;

AnalogIn ain(p16);
DigitalOut myLED(LED1);
Ticker pulseReader;

Heart :: Heart() {
}

void Heart :: startReading() {
    pulseReader.attach(this, &Heart::sample, .002f);
}

void Heart :: stopReading() {
    pulseReader.detach();
    __enable_irq();
}

void Heart :: reset() {
    sampleCounter = 0;          // used to determine pulse timing
    lastBeatTime = 0;           // used to find IBI
    P =512;                      // used to find peak in pulse wave, seeded
    T = 512;                     // used to find trough in pulse wave, seeded
    thresh = 512;                // used to find instant moment of heart beat, seeded
    amp = 100;                   // used to hold amplitude of pulse waveform, seeded
    firstBeat = true;        // used to seed rate array so we startup with reasonable BPM
    secondBeat = false;      // used to seed rate array so we startup with reasonable BPM
    IBI = 600;             // holds the time between beats, must be seeded! 
    Pulse = false;     // true when pulse wave is high, false when it's low
    QS = false;        // becomes true when Arduoino finds a beat.
    isBeating = false;
    beatCount = 0; 
    PulseLength = 0;       
}

bool Heart :: beatDetected() {
    return isBeating;
}

int Heart :: beatsCounted() {
    return beatCount;
}

// THIS IS THE TIMER 2 INTERRUPT SERVICE ROUTINE. 
// Timer 2 makes sure that we take a reading every 2 miliseconds
void Heart :: sample() {                         // triggered when Timer2 counts to 124
  __disable_irq();            
  float readVal = ain;                          // disable interrupts while we do this
  Signal = ain * 1024;              // read the Pulse Sensor 
  sampleCounter += 2;                         // keep track of the time in mS with this variable
  int N = sampleCounter - lastBeatTime;       // monitor the time since the last beat to avoid noise

    //  find the peak and trough of the pulse wave
  if(Signal < thresh && N > (IBI/5)*3){       // avoid dichrotic noise by waiting 3/5 of last IBI
    if (Signal < T){                        // T is the trough
      T = Signal;                         // keep track of lowest point in pulse wave 
    }
  }

  if(Signal > thresh && Signal > P){          // thresh condition helps avoid noise
    P = Signal;                             // P is the peak
  }                                        // keep track of highest point in pulse wave

  //  NOW IT'S TIME TO LOOK FOR THE HEART BEAT
  // signal surges up in value every time there is a pulse
  if (N > 250){                                   // avoid high frequency noise
    if ( (Signal > thresh) && (Pulse == false) && (N > (IBI/5)*3) ){        
      Pulse = true;                               // set the Pulse flag when we think there is a pulse
      IBI = sampleCounter - lastBeatTime;         // measure time between beats in mS
      lastBeatTime = sampleCounter;               // keep track of time for next pulse

      if(secondBeat){                        // if this is the second beat, if secondBeat == TRUE
        secondBeat = false;                  // clear secondBeat flag
        for(int i=0; i<=9; i++){             // seed the running total to get a realisitic BPM at startup
          rate[i] = IBI;                      
        }
      }

      if(firstBeat){                         // if it's the first time we found a beat, if firstBeat == TRUE
        firstBeat = false;                   // clear firstBeat flag
        secondBeat = true;                   // set the second beat flag
        __enable_irq();                               // enable interrupts again
        return;                              // IBI value is unreliable so discard it
      }   


      // keep a running total of the last 10 IBI values
      unsigned short runningTotal = 0;                  // clear the runningTotal variable    

      for(int i=0; i<=8; i++){                // shift data in the rate array
        rate[i] = rate[i+1];                  // and drop the oldest IBI value 
        runningTotal += rate[i];              // add up the 9 oldest IBI values
      }

      rate[9] = IBI;                          // add the latest IBI to the rate array
      runningTotal += rate[9];                // add the latest IBI to runningTotal
      runningTotal /= 10;                     // average the last 10 IBI values 
      BPM = 60000/runningTotal;               // how many beats can fit into a minute? that's BPM!
      QS = true;                              // set Quantified Self flag 
      // QS FLAG IS NOT CLEARED INSIDE THIS ISR
      myLED = 1;
    }                       
  }

  if(Pulse) {
    PulseLength+=2;
    if (Signal < thresh){   // when the values are going down, the beat is over
        myLED = 0;           // turn off pin 13 LED
        Pulse = false;                         // reset the Pulse flag so we can do it again
        amp = P - T;                           // get amplitude of the pulse wave
        //if (PulseLength > 4 && amp > (T/2)) {
        if (PulseLength > 4 && amp > (T/3)) {
            isBeating = true;
            beatCount++;
        }
        thresh = amp/2 + T;                    // set thresh at 50% of the amplitude
        P = thresh;                            // reset these for next time
        T = thresh;
        PulseLength = 0;
    }
  }

  if (N > 2500){                           // if 2.5 seconds go by without a beat
    thresh = 512;                          // set thresh default
    P = 512;                               // set P default
    T = 512;                               // set T default
    lastBeatTime = sampleCounter;          // bring the lastBeatTime up to date        
    firstBeat = true;                      // set these to avoid noise
    secondBeat = false;                    // when we get the heartbeat back
    isBeating = false;
  }

  __enable_irq();                                   // enable interrupts when youre done!
}