/* PulseRateCode: IR Pulse Rate Monitor w/external R2 */

int ledPin = 12; 	int sensorPin = A0; 	
double alpha = 0.75; 	int period = 20; 
double change = 0.0; 

void setup( ) 	{ 
pinMode(ledPin, OUTPUT); 
} 

void loop( ) 	{ 
static double oldVal = 0; 
static double oldChange = 0; 
int rawVal = analogRead(sensorPin); 
double val = alpha * oldVal + (1 - alpha) * rawVal; 
change = val - oldVal; 
digitalWrite(ledPin, (change < 0.0 && oldChange > 0.0)); 
oldVal = val; 
oldChange = change; 
delay(period); 
} 	// END