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Warren Gill
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Code for pulse sensor from pulsesensor.com
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‎PulseSensorAmped_Arduino_1dot2/Interrupt.ino

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// WG: Mod for Micro (TIMER2) and timeout delay for LED
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volatile int rate[10]; // used to hold last ten IBI values
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volatile unsigned long sampleCounter = 0; // used to determine pulse timing
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volatile unsigned long lastBeatTime = 0; // used to find the inter beat interval
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volatile unsigned long lastLEDtime = 0; // measures the minimum time for lighting the LED
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volatile int P =512; // used to find peak in pulse wave
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volatile int T = 512; // used to find trough in pulse wave
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volatile int thresh = 512; // used to find instant moment of heart beat
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volatile int amp = 100; // used to hold amplitude of pulse waveform
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volatile boolean firstBeat = true; // used to seed rate array so we startup with reasonable BPM
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volatile boolean secondBeat = true; // used to seed rate array so we startup with reasonable BPM
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void interruptSetup(){ // Initializes Timer1 to throw an interrupt every 2mS.
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TCCR1A = 0x02; // Disable PWM on pins D9 and D10, go into CTC mode
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TCCR1B = 0x05; // Don't force compare, 64 prescalar
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OCR1A = 0X7C; // Set the top of the count to 124 for 500Hz sample rate
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TIMSK1 = 0x02; // Enable interrupt on match between TIMER1 and OCR1A
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sei(); // Enable global interrupts
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}
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// Service TIMER1 interrupts
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// Timer1 makes sure that we take a reading every 2 milliseconds
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ISR(TIMER1_COMPA_vect){ // triggered when Timer1 counts to 124
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cli(); // disable interrupts while we do this
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Signal = analogRead(pulsePin); // read the Pulse Sensor
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sampleCounter = millis(); // keep track of the time in mS with this variable
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int N = sampleCounter - lastBeatTime; // monitor the time since the last beat to avoid noise
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// Find the peak and trough of the pulse wave
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if (Signal < thresh && N > (IBI/5)*3) { // avoid dichrotic noise by waiting 3/5 of last IBI
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if (Signal < T) { // T is the trough
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T = Signal; // keep track of lowest point in pulse wave
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}
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}
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if (Signal > thresh && Signal > P) { // thresh condition helps avoid noise
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P = Signal; // P is the peak
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} // keep track of highest point in pulse wave
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// Look for the heartbeat
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// Signal surges up in value every time there is a pulse
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if (N > 250) { // avoid high frequency noise
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if ( (Signal > thresh) && (Pulse == false) && (N > (IBI/5)*3) ) {
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Pulse = true; // set the Pulse flag when we think there is a pulse
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digitalWrite(blinkPin, HIGH); // turn on pin 13 LED
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lastLEDtime = sampleCounter; // remember when the LED was turned on
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IBI = sampleCounter - lastBeatTime; // measure time between beats in mS
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lastBeatTime = sampleCounter; // keep track of time for next pulse
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if (firstBeat) { // if it's the first time we found a beat, firstBeat == TRUE
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firstBeat = false; // clear firstBeat flag
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return; // IBI value is unreliable so discard it
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}
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if (secondBeat) { // if this is the second beat, secondBeat == TRUE
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secondBeat = false; // clear secondBeat flag
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for (int i=0; i<=9; i++) { // seed the running total to get a realisitic BPM at startup
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rate[i] = IBI;
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}
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}
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// keep a running total of the last 10 IBI values
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word runningTotal = 0; // clear the runningTotal variable
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for (int i=0; i<=8; i++) { // shift data in the rate array
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rate[i] = rate[i+1]; // and drop the oldest IBI value
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runningTotal += rate[i]; // add up the 9 oldest IBI values
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}
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rate[9] = IBI; // add the latest IBI to the rate array
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runningTotal += rate[9]; // add the latest IBI to runningTotal
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runningTotal /= 10; // average the last 10 IBI values
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BPM = 60000/runningTotal; // how many beats can fit into a minute? that's BPM!
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QS = true; // set Quantified Self flag
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// NOTE: QS flag is not cleared inside the ISR
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}
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}
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if (Signal < thresh && Pulse == true) { // when the values are going down, the beat is over
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if ( sampleCounter > (lastLEDtime + 100) ) { // the LED should be on at least a quarter second so you can see it
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digitalWrite(blinkPin, LOW); // turn off pin 13 LED
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}
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Pulse = false; // reset the Pulse flag so we can do it again
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amp = P - T; // get amplitude of the pulse wave
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thresh = amp/2 + T; // set thresh at 50% of the amplitude
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P = thresh; // reset these for next time
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T = thresh;
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}
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if (N > 2500) { // if 2.5 seconds go by without a beat
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thresh = 512; // set thresh default
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P = 512; // set P default
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T = 512; // set T default
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lastBeatTime = sampleCounter; // bring the lastBeatTime up to date
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firstBeat = true; // set these to avoid noise
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secondBeat = true; // when we get the heartbeat back
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}
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sei(); // enable interrupts when you're done!
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}// end ISR
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‎PulseSensorAmped_Arduino_1dot2/PulseSensorAmped_Arduino_1dot2.ino

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/*
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>> Pulse Sensor Amped 1.2 <<
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This code is for Pulse Sensor Amped by Joel Murphy and Yury Gitman
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www.pulsesensor.com
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>>> Pulse Sensor purple wire goes to Analog Pin 0 <<<
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Pulse Sensor sample aquisition and processing happens in the background via Timer 2 interrupt. 2mS sample rate.
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PWM on pins 3 and 11 will not work when using this code, because we are using Timer 2!
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The following variables are automatically updated:
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Signal : int that holds the analog signal data straight from the sensor. updated every 2mS.
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IBI : int that holds the time interval between beats. 2mS resolution.
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BPM : int that holds the heart rate value, derived every beat, from averaging previous 10 IBI values.
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QS : boolean that is made true whenever Pulse is found and BPM is updated. User must reset.
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Pulse : boolean that is true when a heartbeat is sensed then false in time with pin13 LED going out.
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This code is designed with output serial data to Processing sketch "PulseSensorAmped_Processing-xx"
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The Processing sketch is a simple data visualizer.
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All the work to find the heartbeat and determine the heartrate happens in the code below.
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Pin 13 LED will blink with heartbeat.
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If you want to use pin 13 for something else, adjust the interrupt handler
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It will also fade an LED on pin fadePin with every beat. Put an LED and series resistor from fadePin to GND.
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Check here for detailed code walkthrough:
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http://pulsesensor.myshopify.com/pages/pulse-sensor-amped-arduino-v1dot1
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Code Version 02 by Joel Murphy & Yury Gitman Fall 2012
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This update changes the HRV variable name to IBI, which stands for Inter-Beat Interval, for clarity.
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Switched the interrupt to Timer2. 500Hz sample rate, 2mS resolution IBI value.
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Fade LED pin moved to pin 5 (use of Timer2 disables PWM on pins 3 & 11).
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Tidied up inefficiencies since the last version.
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*
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* WG: Made several improvements in the Interrupt code. It works with Arduino Micro
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* Also added a counter to keep the LED lit for a minimum time (it was blinking too fast to be visible)
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*/
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// VARIABLES
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int pulsePin = 0; // Pulse Sensor purple wire connected to analog pin 0
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int blinkPin = 13; // pin to blink led at each beat
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int fadePin = 11; // pin to do fancy classy fading blink at each beat
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int fadeRate = 0; // used to fade LED on with PWM on fadePin
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// these variables are volatile because they are used during the interrupt service routine!
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volatile int BPM; // used to hold the pulse rate
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volatile int Signal; // holds the incoming raw data
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volatile int IBI = 600; // holds the time between beats, the Inter-Beat Interval
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volatile boolean Pulse = false; // true when pulse wave is high, false when it's low
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volatile boolean QS = false; // becomes true when Arduoino finds a beat.
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void setup(){
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pinMode(blinkPin,OUTPUT); // pin that will blink to your heartbeat!
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pinMode(fadePin,OUTPUT); // pin that will fade to your heartbeat!
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Serial.begin(115200); // we agree to talk fast!
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interruptSetup(); // sets up to read Pulse Sensor signal every 2mS
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// UN-COMMENT THE NEXT LINE IF YOU ARE POWERING The Pulse Sensor AT LOW VOLTAGE,
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// AND APPLY THAT VOLTAGE TO THE A-REF PIN
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//analogReference(EXTERNAL);
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}
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void loop(){
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sendDataToProcessing('S', Signal); // send Processing the raw Pulse Sensor data
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if (QS == true){ // Quantified Self flag is true when arduino finds a heartbeat
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fadeRate = 255; // Set 'fadeRate' Variable to 255 to fade LED with pulse
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sendDataToProcessing('B',BPM); // send heart rate with a 'B' prefix
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sendDataToProcessing('Q',IBI); // send time between beats with a 'Q' prefix
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QS = false; // reset the Quantified Self flag for next time
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}
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ledFadeToBeat();
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delay(10); // take a break
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}
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void ledFadeToBeat(){
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fadeRate -= 15; // set LED fade value
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fadeRate = constrain(fadeRate,0,255); // keep LED fade value from going into negative numbers!
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analogWrite(fadePin,fadeRate); // fade LED
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}
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void sendDataToProcessing(char symbol, int data ){
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Serial.print(symbol); // symbol prefix tells Processing what type of data is coming
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Serial.println(data); // the data to send culminating in a carriage return
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}
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‎pulseMonitorPCD8544/Interrupt.ino

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volatile int rate[10]; // used to hold last ten IBI values
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volatile unsigned long sampleCounter = 0; // used to determine pulse timing
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volatile unsigned long lastBeatTime = 0; // used to find the inter beat interval
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volatile unsigned long lastLEDtime = 0; // measures the minimum time for lighting the LED
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volatile int P =512; // used to find peak in pulse wave
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volatile int T = 512; // used to find trough in pulse wave
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volatile int thresh = 512; // used to find instant moment of heart beat
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volatile int amp = 100; // used to hold amplitude of pulse waveform
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volatile boolean firstBeat = true; // used to seed rate array so we startup with reasonable BPM
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volatile boolean secondBeat = true; // used to seed rate array so we startup with reasonable BPM
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void interruptSetup(){ // Initializes Timer1 to throw an interrupt every 2mS.
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TCCR1A = 0x02; // Disable PWM on pins D9 and D10, go into CTC mode
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TCCR1B = 0x05; // Don't force compare, 64 prescalar
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OCR1A = 0X7C; // Set the top of the count to 124 for 500Hz sample rate
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TIMSK1 = 0x02; // Enable interrupt on match between TIMER1 and OCR1A
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sei(); // Enable global interrupts
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}
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// Service TIMER1 interrupts
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// Timer1 makes sure that we take a reading every 2 milliseconds
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ISR(TIMER1_COMPA_vect){ // triggered when Timer1 counts to 124
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cli(); // disable interrupts while we do this
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Signal = analogRead(pulsePin); // read the Pulse Sensor
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sampleCounter = millis(); // keep track of the time in mS with this variable
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int N = sampleCounter - lastBeatTime; // monitor the time since the last beat to avoid noise
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// Find the peak and trough of the pulse wave
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if (Signal < thresh && N > (IBI/5)*3) { // avoid dichrotic noise by waiting 3/5 of last IBI
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if (Signal < T) { // T is the trough
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T = Signal; // keep track of lowest point in pulse wave
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}
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}
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if (Signal > thresh && Signal > P) { // thresh condition helps avoid noise
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P = Signal; // P is the peak
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} // keep track of highest point in pulse wave
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// Look for the heartbeat
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// Signal surges up in value every time there is a pulse
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if (N > 250) { // avoid high frequency noise
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if ( (Signal > thresh) && (Pulse == false) && (N > (IBI/5)*3) ) {
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Pulse = true; // set the Pulse flag when we think there is a pulse
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digitalWrite(blinkPin, HIGH); // turn on pin 13 LED
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display.setCursor(heartX, heartY); // draw the heart
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display.write(3);
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IBI = sampleCounter - lastBeatTime; // measure time between beats in mS
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lastLEDtime = sampleCounter; // remember when the LED was turned on
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lastBeatTime = sampleCounter; // keep track of time for next pulse
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if (firstBeat) { // if it's the first time we found a beat, firstBeat == TRUE
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firstBeat = false; // clear firstBeat flag
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return; // IBI value is unreliable so discard it
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}
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if (secondBeat) { // if this is the second beat, secondBeat == TRUE
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secondBeat = false; // clear secondBeat flag
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for (int i=0; i<=9; i++) { // seed the running total to get a realisitic BPM at startup
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rate[i] = IBI;
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}
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}
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// keep a running total of the last 10 IBI values
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word runningTotal = 0; // clear the runningTotal variable
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for (int i=0; i<=8; i++) { // shift data in the rate array
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rate[i] = rate[i+1]; // and drop the oldest IBI value
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runningTotal += rate[i]; // add up the 9 oldest IBI values
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}
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rate[9] = IBI; // add the latest IBI to the rate array
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runningTotal += rate[9]; // add the latest IBI to runningTotal
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runningTotal /= 10; // average the last 10 IBI values
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BPM = 60000/runningTotal; // how many beats can fit into a minute? that's BPM!
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QS = true; // set Quantified Self flag
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// NOTE: QS flag is not cleared inside the ISR
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}
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}
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if (Signal < thresh && Pulse == true) { // when the values are going down, the beat is over
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if ( sampleCounter > (lastLEDtime + 100) ) { // the LED should be on at least a quarter second so you can see it
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digitalWrite(blinkPin, LOW); // turn off pin 13 LED
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display.setCursor(heartX, heartY); // draw the heart
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display.write(0); // Erase the heart
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}
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Pulse = false; // reset the Pulse flag so we can do it again
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amp = P - T; // get amplitude of the pulse wave
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thresh = amp/2 + T; // set thresh at 50% of the amplitude
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P = thresh; // reset these for next time
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T = thresh;
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}
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if (N > 2500) { // if 2.5 seconds go by without a beat
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thresh = 512; // set thresh default
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P = 512; // set P default
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T = 512; // set T default
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lastBeatTime = sampleCounter; // bring the lastBeatTime up to date
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firstBeat = true; // set these to avoid noise
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secondBeat = true; // when we get the heartbeat back
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}
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sei(); // enable interrupts when you're done!
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}// end ISR

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