I'm using the Pulse Sensors from https://pulsesensor.com/ and while it works fine with one sensors, I'm struggling to make all 4 sensors work at the same time.
I've had a look at an old forum postand while they recommend for loops in the interrrupt and array variables, I really can't make it work, or really understand how it works.
Any help would be very appreciated!!
I'm attaching my curent code, which is showing me two signals on serial plotter, and making both leds blink at each heart pulse (I'm not using the fade led yet). This code s however giving me weird random results (9 outputs instead of 6?)
#define SERIAL_PLOTTER 2
static int outputType = SERIAL_PLOTTER;
// VARIABLES
int pulsePin1 = 0; // Pulse Sensor purple wire connected to analog pin 0
int pulsePin2 = 1; // Pulse Sensor purple wire connected to analog pin 1
int blinkPin1 = 13; // pin to blink led at each beat
int blinkPin2 = 12;
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 Signal1; // holds the incoming raw data
volatile int Signal2;
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 Arduino finds a beat.
void setup(){
pinMode(blinkPin1,OUTPUT); // pin that will blink to your heartbeat!
pinMode(blinkPin2,OUTPUT);
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);
}
void loop(){
diffSignalOutput(Signal1);
Serial.print(",");
diffSignalOutput(Signal2);
Serial.println("");
}
void diffSignalOutput(int signals){
//Serial.print(BPM);
//Serial.print(",");
//Serial.print(IBI);
//Serial.print(",");
Serial.print(signals);
if (QS == true){ // Quantified Self flag is true when arduino finds a heartbeat
fadeRate = 255; // Set 'fadeRate' Variable to 255 to fade LED with pulse
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
}
And the Interrupt is
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 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
}
void tryISR(int signals, int blinks){
int N = sampleCounter - lastBeatTime; // monitor the time since the last beat to avoid noise
// find the peak and trough of the pulse wave
if(signals < thresh && N > (IBI/5)*3){ // avoid dichrotic noise by waiting 3/5 of last IBI
if (signals < T){ // T is the trough
T = signals; //keep track of lowest point in pulse wave
}
}
if(signals > thresh && signals > P){ // thresh condition helps avoid noise
P = signals; // 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 ( (signals > thresh) && (Pulse == false) && (N > (IBI/5)*3) ){
Pulse = true; // set the Pulse flag when we think there is a pulse
digitalWrite(blinks,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 (signals < thresh && Pulse == true){ // when the values are going down, the beat is over
digitalWrite(blinks,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
}
}
// 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
Signal1 = analogRead(pulsePin1); // read the Pulse Sensor
Signal2 = analogRead(pulsePin2);
sampleCounter += 2; // keep track of the time in mS with this variable
tryISR(Signal1, blinkPin1);
tryISR(Signal2, blinkPin2);
sei(); // enable interrupts when youre done!
}// end isr