/********************************************************************
* FileName:        timers with interrupts.c
* Processor:       PIC18F4520
* Compiler:        MPLAB C18 v.3.06 
*
* This file displays the timer 0 on the PICDEM 2 LCD screen.
*
*  As a bonus it increments the PORTB LEDs using an interrupt when
*   the timer overflows.  
*
* Author               Date        Comment
* Dave Fisher          10/3/2007
*~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~*/

/** Processor Header Files ****************************************/     
#include <p18f4520.h> 
#include "LCD module.h"
#include <stdio.h>
#include <timers.h>

/** Define Constants Here ******************************************/

/** Local Function Prototypes **************************************/
void low_isr(void);
void high_isr(void);

#pragma config OSC = EC  // External 4MHz crystal
#pragma config WDT = OFF
#pragma config LVP = OFF
#pragma config BOREN = OFF
#pragma config XINST = OFF

/** Declare Interrupt Vector Sections ****************************/
#pragma code high_vector=0x08
void interrupt_at_high_vector(void)
{
   _asm goto high_isr _endasm
}

#pragma code low_vector=0x18
void interrupt_at_low_vector(void)
{
   _asm goto low_isr _endasm
}

/** Global Variables *********************************************/
char line1[17];
char line2[17];
unsigned int result0, result1;
	
/*****************************************************************
* Function:        void main(void)
******************************************************************/
#pragma code

void main(void)
{		
  // Setup Output LEDs
  ADCON1 = 0x0F;
  TRISB = 0xF0;
  PORTB = 0x00;
		
  // Initialize the LCD
  XLCDInit();
  XLCDClear();	


  // Configure timer0
  OpenTimer0( TIMER_INT_ON & T0_16BIT & T0_SOURCE_INT & T0_PS_1_128 );

  // Clock Frequency = 4 MHz
  // Instruction cycle Frequency = 1 MHz
  // Timer 0 Frequency = 1 MHz / 128 = 7812.5 Hz
  // Timer 0 Period =  128 uSeconds <-- Always equals prescaler when clock is 4 MHz
  // Overflow every 128 uSecond * 2^16 ticks = 8.4 seconds

  // This code is only necessary for the interrupt
//  INTCONbits.PEIE = 1;  // Enable Peripheral interrupts (to use Timer 1 as interrupt)
  INTCONbits.GIE = 1;			// Enable Interrupts
    	

  while (1) {

    // Read Timer0 and display on line 1
    result0 = ReadTimer0(); // read timer
    sprintf(line1,"Timer 0 -> %#5.5u",result0);
    XLCDL1home();
    XLCDPutRamString(line1);

    // TODO: Read Timer1 and display on line 2 (very similar to above)

  }
}


/*****************************************************************
* Function:        void high_isr(void)
* Input:		Occurs on a timer overflow
* Output:		Modify the PORTB LEDs
* Overview:		The interrupt counts overflows using LEDs
******************************************************************/
#pragma interrupt high_isr			// declare function as high priority isr
void high_isr(void)
{
  if(INTCONbits.TMR0IF)  // Check wether it was the timer 0 interrupt
  {						
    INTCONbits.TMR0IF = 0;	// Clear interrupt flag for TIMER Zero
    PORTB++;
  }
}

/******************************************************************
* Function:        void low_isr(void)
* Input:
* Output:
* Overview:
********************************************************************/
#pragma interruptlow low_isr		// declare function as low priority isr
void low_isr(void)
{
}