// ******************************************************************************************* //

#include "p24fj64ga002.h"

// ******************************************************************************************* //
// Configuration bits for CONFIG1 and CONFIG2. 
//
// Make sure "Configuration Bits set in code." option is checked in MPLAB.
// This option can be set by selecting "Configuration Bits..." under the Configure
// menu in MPLAB.
//
// These settings are appropriate for debugging the PIC microcontroller. If you need to 
// program the PIC for standalone operation, change the COE_ON option to COE_OFF.

_CONFIG1( JTAGEN_OFF & GCP_OFF & GWRP_OFF & BKBUG_ON & COE_ON & ICS_PGx1 & 
		 FWDTEN_OFF & WINDIS_OFF & FWPSA_PR128 & WDTPS_PS32768 )

_CONFIG2( IESO_OFF & SOSCSEL_SOSC & WUTSEL_LEG & FNOSC_PRIPLL & FCKSM_CSDCMD & OSCIOFNC_OFF &
		 IOL1WAY_OFF & I2C1SEL_PRI & POSCMOD_XT )

// ******************************************************************************************* //

#define S_NO_PRESS  0
#define S_1ST_PRESS 1
#define S_2ND_PRESS 2

volatile int pState  = S_NO_PRESS;
volatile int elapsedTime = 0;

// ******************************************************************************************* //

int main(void)
{
	_TRISB15 = 0;         // Configure RB15 as output
	_LATB15 = 1;          // Initialize LED to off
	
	// ******************************************************************************* //
	// Timer 2 is used for Input Capture 
	// ******************************************************************************* //
	
	// Set Timer 2's period value regsiter to value for 750ms.
	//    Fosc/2     = (7372800 * 4)/2 = 14745600
	//    Timer Freq = 14745600 / 256 = 57600
	//    PRx        = 750e-3 * 57600 - 1 = 43199
	T2CONbits.TCKPS = 3;  // Set Timer2's Prescaler to 1:256
	PR2 = 43199;
	TMR2 = 0;		      // Clear Timer 2  to 0	
	_T2IF = 0;	          // Clear Timer 2 interrupt flag	
	
	// ******************************************************************************* //
	// Input Capture 1 is used timing of button presses from SW5 (RP5) 
	// ******************************************************************************* //
	
	RPINR7bits.IC1R = 5;  // RP5 is input for Input Capture 1
	IC1CONbits.ICM = 2;   // Capture on every falling edge (i.e. button press)
	IC1CONbits.ICTMR = 1; // Timer 2 used
	IC1CONbits.ICI = 0;   // Interrupt on every capture
	_IC1IF = 0;           // Clear Input Capture 1 interrupt flag
	_IC1IE = 1;           // Enable Interrupt Capture 1 interrupt
	
	// ******************************************************************************* //
	
	while(1)
	{
		// Nothing to see here. Move along everybody.
	}
	return 0;
}

// ******************************************************************************************* //
// Timer 2 interrupt will be executed if 750 ms have pasted since first press.

void _ISR _T2Interrupt(void)
{	
	_T2IF = 0;                // Clear Timer 2 interrupt flag
 	
	// Check if we have detected two presses...
	if( pState == S_2ND_PRESS ) {
		_LATB15 = ~_LATB15;   // Toggle LED
		pState = S_1ST_PRESS; // Reset to first press state
	}	
	// Otherwise, only first press detected, reset to no press state...
	else {
		pState = S_NO_PRESS;  // Reset to no press state
		T2CONbits.TON = 0;    // Stop Timer 2
		TMR2 = 0;             // Reset Timer 2
		_T2IE = 0;            // Disable Timer 2 interrupt
	}	
}

// ******************************************************************************************* //
// Input Capture Interrupt used to measure time between first and second press. Further
// implements a simple state machine for monitoring the number of button presses
// we have observed so far.

void _ISR _IC1Interrupt(void)
{	
	int dummy;
	
	_IC1IF = 0;                   // Clear Input Capture interrupt flag
	
	switch (pState) {
		case S_NO_PRESS:
			pState = S_1ST_PRESS; // Found first press
			TMR2 = 0;             // Reset Timer 2
			_T2IE = 1;            // Enable Timer 2 Interrupt
			T2CONbits.TON = 1;    // Start Timer 2
			elapsedTime = IC1BUF; // Read the buffer to avoid overflow
			break;
			
		case S_1ST_PRESS:
			pState = S_2ND_PRESS; // Found second press
			elapsedTime = IC1BUF; // Keep track of time between first and second press
			break;
			
		case S_2ND_PRESS:
			T2CONbits.TON = 0;	  // Stop Timer 2
			TMR2 -= elapsedTime;  // Adjust Timer 2 to time of last press (now the first press)
			T2CONbits.TON = 1;	  // Start Timer 2
			elapsedTime = IC1BUF - elapsedTime; // Log time between new first and second press
			break;
	}
}

// ******************************************************************************************* //