///////////////////////////////////////
// Lab 5 - Microcontrollers, Triggers
// M K Gharzai
// Oct 08 2017
///////////////////////////////////////

uint16_t captureTime, captureTimePrev, diff;

void setup()
{
  Serial.begin(115200);

  // consult the AVR manual and set the following registers,

  // you can use binary or hex, e.g:
  // 	0b00001000 == 0x04

  // A  = 0x80; // to set a value    (A = 0b10000000)
  // A |= 0x2A; // to pull bits high (A = 0b10101010)
  // A &= 0x08; // to pull bits low  (A = 0b00001000)

  DDRB   = 0x00;        // all pins on PORTB should be defined as inputs
  TCCR1A &= 0b11111100; //should only affect bits 0 and 1 to activate normal counter operation
  TCCR1B |= 0b11000010; //Bit 7 activates noise cancellation, 6 sets rising edge trigger, bit 1 is part of clock scaling
  TCCR1B &= 0b11100010; //These bits are set to only affect the WGM and other pins in the line above
  TIMSK1 |= 0b00100000; //This turns on the ICIE1 Interrupt Enable
  SREG  |= 0x80; // enable global interrupts
}

void loop()
{
  diff = captureTime - captureTimePrev;
  Serial.print("difference: "); Serial.print(diff);
  Serial.print("\tfrequency: "); Serial.println(2e6/diff);
}

ISR(TIMER1_CAPT_vect) {
  captureTimePrev = captureTime;
  unsigned short *inputCaptureRegister1;
  inputCaptureRegister1 = (unsigned short *) 0x86;
  captureTime  = *inputCaptureRegister1;
}