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February 8, 2015 05:37
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Pulse Rate
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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 = 525; // used to find instant moment of heart beat, seeded | |
volatile int amp = 100; // used to hold amplitude of pulse waveform, seeded | |
volatile boolean firstBeat = true; // used to seed rate array so we startup with reasonable BPM | |
volatile boolean secondBeat = false; // used to seed rate array so we startup with reasonable BPM | |
void interruptSetup(){ | |
// Initializes Timer2 to throw an interrupt every 2mS. | |
TCCR2A = 0x02; // DISABLE PWM ON DIGITAL PINS 3 AND 11, AND GO INTO CTC MODE | |
TCCR2B = 0x06; // DON'T FORCE COMPARE, 256 PRESCALER | |
OCR2A = 0X7C; // SET THE TOP OF THE COUNT TO 124 FOR 500Hz SAMPLE RATE | |
TIMSK2 = 0x02; // ENABLE INTERRUPT ON MATCH BETWEEN TIMER2 AND OCR2A | |
sei(); // MAKE SURE GLOBAL INTERRUPTS ARE ENABLED | |
} | |
// THIS IS THE TIMER 2 INTERRUPT SERVICE ROUTINE. | |
// Timer 2 makes sure that we take a reading every 2 miliseconds | |
ISR(TIMER2_COMPA_vect){ // triggered when Timer2 counts to 124 | |
cli(); // disable interrupts while we do this | |
Signal = analogRead(pulsePin); // 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(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 | |
sei(); // enable interrupts again | |
return; // IBI value is unreliable so discard it | |
} | |
// keep a running total of the last 10 IBI values | |
word 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 | |
digitalWrite(blinkPin,LOW); // 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 | |
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 = false; // when we get the heartbeat back | |
} | |
sei(); // enable interrupts when youre done! | |
}// end isr |
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/* | |
>> Pulse Sensor Amped 1.2 << | |
This code is for Pulse Sensor Amped by Joel Murphy and Yury Gitman | |
www.pulsesensor.com | |
>>> Pulse Sensor purple wire goes to Analog Pin 0 <<< | |
Pulse Sensor sample aquisition and processing happens in the background via Timer 2 interrupt. 2mS sample rate. | |
PWM on pins 3 and 11 will not work when using this code, because we are using Timer 2! | |
The following variables are automatically updated: | |
Signal : int that holds the analog signal data straight from the sensor. updated every 2mS. | |
IBI : int that holds the time interval between beats. 2mS resolution. | |
BPM : int that holds the heart rate value, derived every beat, from averaging previous 10 IBI values. | |
QS : boolean that is made true whenever Pulse is found and BPM is updated. User must reset. | |
Pulse : boolean that is true when a heartbeat is sensed then false in time with pin13 LED going out. | |
This code is designed with output serial data to Processing sketch "PulseSensorAmped_Processing-xx" | |
The Processing sketch is a simple data visualizer. | |
All the work to find the heartbeat and determine the heartrate happens in the code below. | |
Pin 13 LED will blink with heartbeat. | |
If you want to use pin 13 for something else, adjust the interrupt handler | |
It will also fade an LED on pin fadePin with every beat. Put an LED and series resistor from fadePin to GND. | |
Check here for detailed code walkthrough: | |
http://pulsesensor.myshopify.com/pages/pulse-sensor-amped-arduino-v1dot1 | |
Code Version 1.2 by Joel Murphy & Yury Gitman Spring 2013 | |
This update fixes the firstBeat and secondBeat flag usage so that realistic BPM is reported. | |
*/ | |
#include <Adafruit_NeoPixel.h> | |
#include <avr/power.h> | |
#define NUMPIXELS 16 | |
#define PIN 13 | |
Adafruit_NeoPixel pixels = Adafruit_NeoPixel(NUMPIXELS, PIN, NEO_GRB + NEO_KHZ800); | |
// VARIABLES | |
int pulsePin = 0; // Pulse Sensor purple wire connected to analog pin 0 | |
int blinkPin = 13; // pin to blink led at each beat | |
int fadePin = 5; // pin to do fancy classy fading blink at each beat | |
int fadeRate = 0; // used to fade LED on with PWM on fadePin | |
// 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 = 600; // holds the time between beats, must be seeded! | |
volatile boolean Pulse = false; // true when pulse wave is high, false when it's low | |
volatile boolean QS = false; // becomes true when Arduoino finds a beat. | |
void setup(){ | |
pinMode(blinkPin,OUTPUT); // pin that will blink to your heartbeat! | |
pinMode(fadePin,OUTPUT); // pin that will fade to your heartbeat! | |
Serial.begin(115200); // we agree to talk fast! | |
interruptSetup(); // sets up to read Pulse Sensor signal every 2mS | |
// UN-COMMENT THE NEXT LINE IF YOU ARE POWERING The Pulse Sensor AT LOW VOLTAGE, | |
// AND APPLY THAT VOLTAGE TO THE A-REF PIN | |
// analogReference(EXTERNAL); | |
pixels.begin(); | |
} | |
void loop(){ | |
sendDataToProcessing('S', Signal); // send Processing the raw Pulse Sensor data | |
// Quantified Self flag is true when arduino finds a heartbeat | |
if (QS == true){ | |
int bpm = BPM; | |
Serial.println(bpm); | |
for(int i=0;i<NUMPIXELS;i++){ | |
if (bpm >= 101){ | |
pixels.setPixelColor(i, pixels.Color(255, 0, 0)); | |
} | |
else if (bpm >= 81){ | |
pixels.setPixelColor(i, pixels.Color(255, 255, 0)); | |
} | |
else { | |
pixels.setPixelColor(i, pixels.Color(0, 255, 0)); | |
} | |
pixels.show(); | |
delay(10); | |
pixels.setPixelColor(i, pixels.Color(0,0,0)); | |
pixels.show(); | |
delay(10); | |
} | |
} | |
fadeRate = 255; // Set 'fadeRate' Variable to 255 to fade LED with pulse | |
sendDataToProcessing('B',BPM); // send heart rate with a 'B' prefix | |
sendDataToProcessing('Q',IBI); // send time between beats with a 'Q' prefix | |
QS = false; // reset the Quantified Self flag for next time | |
ledFadeToBeat(); | |
delay(20); // take a break | |
} | |
void ledFadeToBeat(){ | |
fadeRate -= 15; // set LED fade value | |
fadeRate = constrain(fadeRate,0,255); // keep LED fade value from going into negative numbers! | |
analogWrite(fadePin,fadeRate); // fade LED | |
} | |
void sendDataToProcessing(char symbol, int data ){ | |
//Serial.print(symbol); // symbol prefix tells Processing what type of data is coming | |
//Serial.println(data); // the data to send culminating in a carriage return | |
} |
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