Mako SHIMURA / Mbed 2 deprecated HeartPulseModify

LED Pierce and pulse program.

Dependencies:   mbed

Interrupt.cpp@1:171a73d84261, 2014-01-11 (annotated)

Committer:
asagin
Date:
Sat Jan 11 12:52:56 2014 +0000
Revision:
1:171a73d84261
Parent:
0:a78b08608d76 
interrupt is not understandable.

Who changed what in which revision?

UserRevisionLine numberNew contents of line
asagin 0:a78b08608d76 1
asagin 0:a78b08608d76 2 volatile int rate[10]; // used to hold last ten IBI values
asagin 0:a78b08608d76 3 volatile unsigned long sampleCounter = 0; // used to determine pulse timing
asagin 0:a78b08608d76 4 volatile unsigned long lastBeatTime = 0; // used to find the inter beat interval
asagin 0:a78b08608d76 5 volatile int P =512; // used to find peak in pulse wave
asagin 0:a78b08608d76 6 volatile int T = 512; // used to find trough in pulse wave
asagin 0:a78b08608d76 7 volatile int thresh = 512; // used to find instant moment of heart beat
asagin 0:a78b08608d76 8 volatile int amp = 100; // used to hold amplitude of pulse waveform
asagin 0:a78b08608d76 9 volatile bool firstBeat = true; // used to seed rate array so we startup with reasonable BPM
asagin 0:a78b08608d76 10 volatile bool secondBeat = true; // used to seed rate array so we startup with reasonable BPM
asagin 0:a78b08608d76 11
asagin 1:171a73d84261 12 //(´・ω・`)
asagin 0:a78b08608d76 13 void interruptSetup(){
asagin 0:a78b08608d76 14 // Initializes Timer2 to throw an interrupt every 2mS.
asagin 0:a78b08608d76 15 TCCR2A = 0x02; // DISABLE PWM ON DIGITAL PINS 3 AND 11, AND GO INTO CTC MODE
asagin 0:a78b08608d76 16 TCCR2B = 0x06; // DON'T FORCE COMPARE, 256 PRESCALER
asagin 0:a78b08608d76 17 OCR2A = 0X7C; // SET THE TOP OF THE COUNT TO 124 FOR 500Hz SAMPLE RATE
asagin 0:a78b08608d76 18 TIMSK2 = 0x02; // ENABLE INTERRUPT ON MATCH BETWEEN TIMER2 AND OCR2A
asagin 0:a78b08608d76 19 sei(); // MAKE SURE GLOBAL INTERRUPTS ARE ENABLED
asagin 0:a78b08608d76 20 }
asagin 0:a78b08608d76 21
asagin 0:a78b08608d76 22
asagin 0:a78b08608d76 23 // THIS IS THE TIMER 2 INTERRUPT SERVICE ROUTINE.
asagin 0:a78b08608d76 24 // Timer 2 makes sure that we take a reading every 2 miliseconds
asagin 0:a78b08608d76 25 ISR(TIMER2_COMPA_vect){ // triggered when Timer2 counts to 124
asagin 0:a78b08608d76 26 cli(); // disable interrupts while we do this
asagin 0:a78b08608d76 27 Signal = analogRead(pulsePin); // read the Pulse Sensor
asagin 0:a78b08608d76 28 sampleCounter += 2; // keep track of the time in mS with this variable
asagin 0:a78b08608d76 29 int N = sampleCounter - lastBeatTime; // monitor the time since the last beat to avoid noise
asagin 0:a78b08608d76 30
asagin 0:a78b08608d76 31 // find the peak and trough of the pulse wave
asagin 0:a78b08608d76 32 if(Signal < thresh && N > (IBI/5)*3){ // avoid dichrotic noise by waiting 3/5 of last IBI
asagin 0:a78b08608d76 33 if (Signal < T){ // T is the trough
asagin 0:a78b08608d76 34 T = Signal; // keep track of lowest point in pulse wave
asagin 0:a78b08608d76 35 }
asagin 0:a78b08608d76 36 }
asagin 0:a78b08608d76 37
asagin 0:a78b08608d76 38 if(Signal > thresh && Signal > P){ // thresh condition helps avoid noise
asagin 0:a78b08608d76 39 P = Signal; // P is the peak
asagin 0:a78b08608d76 40 } // keep track of highest point in pulse wave
asagin 0:a78b08608d76 41
asagin 0:a78b08608d76 42 // NOW IT'S TIME TO LOOK FOR THE HEART BEAT
asagin 0:a78b08608d76 43 // signal surges up in value every time there is a pulse
asagin 0:a78b08608d76 44 if (N > 250){ // avoid high frequency noise
asagin 0:a78b08608d76 45 if ( (Signal > thresh) && (Pulse == false) && (N > (IBI/5)*3) ){
asagin 0:a78b08608d76 46 Pulse = true; // set the Pulse flag when we think there is a pulse
asagin 0:a78b08608d76 47 digitalWrite(blinkPin,HIGH); // turn on pin 13 LED
asagin 0:a78b08608d76 48 IBI = sampleCounter - lastBeatTime; // measure time between beats in mS
asagin 0:a78b08608d76 49 lastBeatTime = sampleCounter; // keep track of time for next pulse
asagin 0:a78b08608d76 50
asagin 0:a78b08608d76 51 if(firstBeat){ // if it's the first time we found a beat, if firstBeat == TRUE
asagin 0:a78b08608d76 52 firstBeat = false; // clear firstBeat flag
asagin 0:a78b08608d76 53 return; // IBI value is unreliable so discard it
asagin 0:a78b08608d76 54 }
asagin 0:a78b08608d76 55 if(secondBeat){ // if this is the second beat, if secondBeat == TRUE
asagin 0:a78b08608d76 56 secondBeat = false; // clear secondBeat flag
asagin 0:a78b08608d76 57 for(int i=0; i<=9; i++){ // seed the running total to get a realisitic BPM at startup
asagin 0:a78b08608d76 58 rate[i] = IBI;
asagin 0:a78b08608d76 59 }
asagin 0:a78b08608d76 60 }
asagin 0:a78b08608d76 61
asagin 0:a78b08608d76 62 // keep a running total of the last 10 IBI values
asagin 0:a78b08608d76 63 word runningTotal = 0; // clear the runningTotal variable
asagin 0:a78b08608d76 64
asagin 0:a78b08608d76 65 for(int i=0; i<=8; i++){ // shift data in the rate array
asagin 0:a78b08608d76 66 rate[i] = rate[i+1]; // and drop the oldest IBI value
asagin 0:a78b08608d76 67 runningTotal += rate[i]; // add up the 9 oldest IBI values
asagin 0:a78b08608d76 68 }
asagin 0:a78b08608d76 69
asagin 0:a78b08608d76 70 rate[9] = IBI; // add the latest IBI to the rate array
asagin 0:a78b08608d76 71 runningTotal += rate[9]; // add the latest IBI to runningTotal
asagin 0:a78b08608d76 72 runningTotal /= 10; // average the last 10 IBI values
asagin 0:a78b08608d76 73 BPM = 60000/runningTotal; // how many beats can fit into a minute? that's BPM!
asagin 0:a78b08608d76 74 QS = true; // set Quantified Self flag
asagin 0:a78b08608d76 75 // QS FLAG IS NOT CLEARED INSIDE THIS ISR
asagin 0:a78b08608d76 76 }
asagin 0:a78b08608d76 77 }
asagin 0:a78b08608d76 78
asagin 0:a78b08608d76 79 if (Signal < thresh && Pulse == true){ // when the values are going down, the beat is over
asagin 0:a78b08608d76 80 digitalWrite(blinkPin,LOW); // turn off pin 13 LED
asagin 0:a78b08608d76 81 Pulse = false; // reset the Pulse flag so we can do it again
asagin 0:a78b08608d76 82 amp = P - T; // get amplitude of the pulse wave
asagin 0:a78b08608d76 83 thresh = amp/2 + T; // set thresh at 50% of the amplitude
asagin 0:a78b08608d76 84 P = thresh; // reset these for next time
asagin 0:a78b08608d76 85 T = thresh;
asagin 0:a78b08608d76 86 }
asagin 0:a78b08608d76 87
asagin 0:a78b08608d76 88 if (N > 2500){ // if 2.5 seconds go by without a beat
asagin 0:a78b08608d76 89 thresh = 512; // set thresh default
asagin 0:a78b08608d76 90 P = 512; // set P default
asagin 0:a78b08608d76 91 T = 512; // set T default
asagin 0:a78b08608d76 92 lastBeatTime = sampleCounter; // bring the lastBeatTime up to date
asagin 0:a78b08608d76 93 firstBeat = true; // set these to avoid noise
asagin 0:a78b08608d76 94 secondBeat = true; // when we get the heartbeat back
asagin 0:a78b08608d76 95 }
asagin 0:a78b08608d76 96
asagin 0:a78b08608d76 97 sei(); // enable interrupts when youre done!
asagin 0:a78b08608d76 98 }// end isr