Revision 0:e80a245c4d0d, committed 2014-02-09

Comitter:

donalm

Date:

Sun Feb 09 15:37:19 2014 +0000

Commit message:

Initial version.

Changed in this revision

diff -r 000000000000 -r e80a245c4d0d PulseSensor.cpp
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/PulseSensor.cpp	Sun Feb 09 15:37:19 2014 +0000
@@ -0,0 +1,152 @@
+#include "PulseSensor.h"
+
+
+PulseSensor::PulseSensor(PinName analogPin, void (*printDataCallback)(char,int), int callbackRateMs)
+{
+    _started = false;
+    
+    _pAin = new AnalogIn(analogPin);
+    
+    _callbackRateMs = callbackRateMs;
+    
+    _printDataCallback = printDataCallback;
+}
+
+
+PulseSensor::~PulseSensor()
+{
+    delete _pAin;
+}
+
+
+void PulseSensor::process_data_ticker_callback(void)
+{
+    _printDataCallback('S', Signal);     // send Processing the raw Pulse Sensor data
+    if (QS == true) { // Quantified Self flag is true when a heartbeat is found
+        //fadeRate = 255;                  // Set 'fadeRate' Variable to 255 to fade LED with pulse
+        _printDataCallback('B',BPM);   // send heart rate with a 'B' prefix
+        _printDataCallback('Q',IBI);   // send time between beats with a 'Q' prefix
+        QS = false;                      // reset the Quantified Self flag for next time
+    }
+}
+
+
+void PulseSensor::sensor_ticker_callback(void)
+{
+    Signal = 1023 * _pAin->read();              // 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
+            //digitalWrite(blinkPin,HIGH);                // turn on pin 13 LED
+            IBI = sampleCounter - lastBeatTime;         // measure time between beats in mS
+            lastBeatTime = sampleCounter;               // keep track of time for next pulse
+
+            if(firstBeat) {                        // if it's the first time we found a beat, if firstBeat == TRUE
+                firstBeat = false;                 // clear firstBeat flag
+                return;                            // IBI value is unreliable so discard it
+            }
+            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;
+                }
+            }
+
+            // keep a running total of the last 10 IBI values
+            long 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
+        }
+    }
+
+    if (Signal < thresh && Pulse == true) {    // when the values are going down, the beat is over
+        Pulse = false;                         // reset the Pulse flag so we can do it again
+        amp = P - T;                           // get amplitude of the pulse wave
+        thresh = amp/2 + T;                    // set thresh at 50% of the amplitude
+        P = thresh;                            // reset these for next time
+        T = thresh;
+    }
+
+    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 = true;                     // when we get the heartbeat back
+    }
+}
+
+
+bool PulseSensor::start()
+{
+    if (_started == false)
+    {
+        sampleCounter = 0;
+        lastBeatTime = 0;
+        P =512;
+        T = 512;
+        thresh = 512;
+        amp = 100;
+        firstBeat = true;
+        secondBeat = true;
+        
+        BPM=0;
+        Signal=0;
+        IBI = 600;
+        Pulse = false;
+        QS = false;
+        
+        _pulseSensorTicker.attach(this, &PulseSensor::sensor_ticker_callback, ((float)_sensorTickRateMs/1000));
+        _processDataTicker.attach(this, &PulseSensor::process_data_ticker_callback,  ((float)_callbackRateMs/1000));
+        _started = true;
+        return true;
+    }
+    else
+    {
+        return false;
+    }
+}
+
+bool PulseSensor::stop()
+{
+    if(_started == true)
+    {
+        _pulseSensorTicker.detach();
+        _processDataTicker.detach();
+        _started = false;
+        return true;
+    }
+    else
+    {
+        return false;
+    }
+}
\ No newline at end of file

diff -r 000000000000 -r e80a245c4d0d PulseSensor.h
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/PulseSensor.h	Sun Feb 09 15:37:19 2014 +0000
@@ -0,0 +1,72 @@
+#ifndef PULSE_SENSOR_H
+#define PULSE_SENSOR_H
+
+#include "mbed.h"
+
+
+/**
+ * Class for interfacing with a http://pulsesensor.myshopify.com/ 'Pulse Sensor Amped'.
+ * The contents of this class are based on the "Pulse Sensor Amped 1.1" Arduino Sketch.
+ *
+ * When using this class for the first time, it is recommended that you use the Processing 
+ * GUI app available http://pulsesensor.myshopify.com/pages/code-and-guide. Using this, you
+ * will easily be able to verify the operating of your sensor, and the integration of this
+ * class into your mbed project. 
+ */
+ 
+class PulseSensor
+{
+    private:
+        volatile int rate[10];                    // used to hold last ten IBI values
+        volatile unsigned long sampleCounter;          // used to determine pulse timing
+        volatile unsigned long lastBeatTime;           // used to find the inter beat interval
+        volatile int P;                      // used to find peak in pulse wave
+        volatile int T;                     // used to find trough in pulse wave
+        volatile int thresh;                // used to find instant moment of heart beat
+        volatile int amp;                   // used to hold amplitude of pulse waveform
+        volatile bool firstBeat;        // used to seed rate array so we startup with reasonable BPM
+        volatile bool secondBeat;       // used to seed rate array so we startup with reasonable BPM
+        
+        // these variables are volatile because they are used during the interrupt service routine!
+        volatile int BPM;                   // used to hold the pulse rate
+        volatile int Signal;                // holds the incoming raw data
+        volatile int IBI;             // holds the time between beats, the Inter-Beat Interval
+        volatile bool Pulse;        // true when pulse wave is high, false when it's low
+        volatile bool QS;           // becomes true when a beat is found
+    
+    
+        void (*_printDataCallback)(char,int);
+        static const int _sensorTickRateMs = 2;
+        int       _callbackRateMs;
+        bool      _started;
+        
+        AnalogIn *_pAin;
+        Ticker    _pulseSensorTicker;
+        Ticker    _processDataTicker;
+        
+        void sensor_ticker_callback(void);
+        void process_data_ticker_callback(void);
+    
+    public:
+        /** PulseSensor Constructor - Note this does not start the reading of the sensor.
+         * @param   analogPin Name of the analog pin that the sensor is connected to.
+         * @param   printDataCallback Pointer to function which will be called to print the latest data. Output format available here: http://pulsesensor.myshopify.com/pages/code-and-guide
+         * @param   callbackRateMs Rate at which the printDataCallback is to be called, recommended is 20ms for graphing of pulse signal.
+         */
+        PulseSensor(PinName analogPin, void (*printDataCallback)(char,int), int callbackRateMs=20);
+        
+        /** Destructor */
+        ~PulseSensor();
+        
+        /** Start reading the Pulse Sensor, and sending current readings to the print data callback.
+         * @returns true if reading of the sensor is started, false if reading was aleady in progress.
+         */
+        bool start();
+        
+        /** Stops the current reading of the Pulse Senson.
+         * @return true if reading is stopped, false if reading was already stopped.
+         */
+        bool stop();
+};
+
+#endif
\ No newline at end of file