Hertz.pde

////
//void InitPeriodHertz() {
//  attachInterrupt(INT_HERTZ,DoPeriodHertz,RISING); //Interrupt #5 - Arduino Pin 18 = PD5
//}
//
//void DoPeriodHertz() {
//  hertz_period = micros() - hertz_last_interrupt;
//  hertz_last_interrupt = micros();
//}
//
//double CalculatePeriodHertz() {
//    if (micros() - hertz_last_interrupt < 500000) { // if period is longer than 500k µs, Hz is less than 2 Hz or getting no signal
//      return 1.0/(hertz_period/1000000.0); //frequency = 1/period in seconds (hertz_period is in microseconds)
//    } else {
//      return 0;  // less than 2 Hz or no signal, so print 0
//    }
//}
//
////CounterHertz - Using hardware counter
//void InitCounterHertz() {
//  unsigned long time;
//  // assumptions:
//  //  TC2 is in mode 0 ("normal mode")  (this is true at processor reset)
//  //  TC2 prescaler is set to "stopped" (CS2, CS1, CS0 are all zero)
//  //  TC2 interrupts are all disabled
//  // set external clock input
//  ASSR |= 1 << 6;
//  // switch to asynchronous operation
//  ASSR |= 1 << 5;
//  // clear counter
//  TCNT2 = 0;
//  // reset TCCR2A to default state (may have been trashed by switching to asynch)
//  TCCR2A = 0x00;
//  // engage prescaler at 1x:
//  TCCR2B &= B11111000; //make sure last three bits are set to zero
//  TCCR2B |= 0x01;
//  // wait for all "update busy" flags to clear
//  // WARNING:  THIS WILL HANG THE PROCESSOR IF NO EXTERNAL PULSE INPUT IS PRESENT!
//  // I suggest trying without this at first, and seeing if we get acceptable results
//  //time = microseconds();
//  //while (ASSR & 0x1f & microseconds()-time < 1000) ;
//  // clear interrupts
//  TIFR2 = 0x00;
//}
//
//void DoCounterHertz() {
//  counter_hertz = int(TCNT2);
//  TCNT2 = 0x00;
//}