Pulse Sensor Arduino Sketch

pulseSensor.ino

volatile unsigned long count = 0;
unsigned long oldcount = 0;
unsigned long last;
unsigned long freq = 0;

void irq1()
{
  count++;
}

void setup() 
{
  Serial.begin(115200);
  pinMode(7, INPUT);
  attachInterrupt(digitalPinToInterrupt(7), irq1, RISING);
}

void loop() 
{
  if (millis() - last >= 100)
  {
    last = millis();
    Serial.println((count - oldcount) * 10);
    oldcount = count;
  }
}