/*

Description:	An AVR ATmega8 based Digital Stop Watch
				Project.
________________________________________________________

Author:	Avinash Gupta
Date:	04 July 09
Web		www.eXtremeElectronics.co.in

	
*/

#include <avr/io.h>
#include <avr/interrupt.h>
#include <util/delay_basic.h>

#define true 1
#define false 0

#define SEVEN_SEGMENT_PORT PORTD
#define SEVEN_SEGMENT_DDR DDRD

volatile uint8_t digits[4];

//Global variable for the clock system
volatile unsigned int   clock_millisecond=0;
volatile unsigned char  clock_second=0;
volatile unsigned char  clock_minute=0;
volatile unsigned char  clock_hour=0;

//Display hiding system
uint8_t hide_display = false;

//Blinking system
uint8_t blink_display = true;



void SevenSegment(uint8_t n,uint8_t dp)
{
/*
This function writes a digits given by n to the display
the decimal point is displayed if dp=1

Note:
n must be less than 9
*/
	if(n<11)
	{
		switch (n)
		{
			case 0:
			SEVEN_SEGMENT_PORT=0b00000011;
			break;

			case 1:
			SEVEN_SEGMENT_PORT=0b10011111;
			break;

			case 2:
			SEVEN_SEGMENT_PORT=0b00100101;
			break;

			case 3:
			SEVEN_SEGMENT_PORT=0b00001101;
			break;

			case 4:
			SEVEN_SEGMENT_PORT=0b10011001;
			break;

			case 5:
			SEVEN_SEGMENT_PORT=0b01001001;
			break;

			case 6:
			SEVEN_SEGMENT_PORT=0b01000001;
			break;

			case 7:
			SEVEN_SEGMENT_PORT=0b00011111;
			break;

			case 8:
			SEVEN_SEGMENT_PORT=0b00000001;
			break;

			case 9:
			SEVEN_SEGMENT_PORT=0b00001001;
			break;

			case 10:
			//A BLANK DISPLAY
			SEVEN_SEGMENT_PORT=0b11111111;
			break;

		}
		if(dp)
		{
			//if decimal point should be displayed
			//make 0th bit Low
			SEVEN_SEGMENT_PORT&=0b11111110;
		}
	}
	else
	{
		//This symbol on display tells that n was greater than 10
		//so display can't handle it
		SEVEN_SEGMENT_PORT=0b11111101;
	}
}

void Wait()
{ 
	uint8_t i;
	for(i=0;i<10;i++)
	{
		_delay_loop_2(0);
	}
}

void Print(uint16_t num)
{
	/* 
	
	This function breaks apart a given integer into separete digits
	and writes them to the display array i.e. digits[]
	
	*/ 
	uint8_t i=0;
	uint8_t j;
	if(num>9999) return;


	while(num)
	{
		digits[i]=num%10;
		i++;

		num=num/10;
	}

	//Fill with leading 0s
	for(j=i;j<4;j++) digits[j]=0;
}
	 
	


void main()
{
	uint16_t i;

	// Prescaler = FCPU/1024
	TCCR0|=(1<<CS02);

	//Enable Overflow Interrupt Enable
	TIMSK|=(1<<TOIE0);

	//Initialize Counter
	TCNT0=0;

	//Port c[3,2,1,0] as out put
	DDRC|=0b00001111;

	PORTC=0b00001110;

	//Port D
	SEVEN_SEGMENT_DDR=0XFF;

	//Turn off all segments
	SEVEN_SEGMENT_PORT=0XFF;

	//Set up the timer1 as described in the
   	//tutorial
   	//TCCR1B=(1<<WGM12)|(1<<CS11)|(1<<CS10);
	//initailly stop the timer by setting clock source =000
	TCCR1B&=(~((1<<CS12)|(1<<CS11)|(1<<CS10)));
   	OCR1A=250;

   	//Enable the Output Compare A interrupt
   	TIMSK|=(1<<OCIE1A);

   	//Enable interrupts globally
   	sei();

   	//Continuasly display the time
   	while(1)
   	{
   		int disp;
		//disp=(clock_hour*100)+clock_minute;
		disp=(clock_minute*100)+clock_second;

		Print(disp);

		if(!(PINB & (1<<PB2)))
		{
			//RESET PRESSED
			clock_millisecond=0;
			clock_second=0;
			clock_minute=0;
			clock_hour=0;
		}

		if(!(PINB & (1<<PB1)))
		{
			//halt pressed
			//stop the timer 
			TCCR1B&=(~((1<<CS12)|(1<<CS11)|(1<<CS10)));

			//Start blinking the display
			blink_display=true;
		}

		if(!(PINB & (1<<PB0)))
		{
			//start pressed
			//start the timer 
			//Set up the timer1 as described in the
   			//tutorial
   			TCCR1B=(1<<WGM12)|(1<<CS11)|(1<<CS10);

			//Stop blinking the display
			blink_display=false;

			//Show the display
			hide_display=false;
		}

      	_delay_loop_2(0);
		_delay_loop_2(0);

   	}


}

ISR(TIMER0_OVF_vect)
{
	
		
	/*

	This interrup service routine (ISR)
	Updates the displays

	*/
	static uint8_t i=0;

	if(i==3)
	{
		//If on last display then come
		//back to first.
		i=0;
	}
	else
	{
		//Goto Next display
		i++;
	}

	//Acivate a display according to i
	PORTC=~(1<<i);

	if(hide_display)
	{
		//Show a blank display
		SevenSegment(10,0);

	}
	else
	{
		//Write the digit[i] in the ith display.
		SevenSegment(digits[i],0);
	}

	//Handle blinking

	if(!blink_display) return;

	static uint8_t blink_counter=0;

	blink_counter++;
	if(blink_counter == 16)
	{
		blink_counter =0;

		hide_display=!hide_display;
	}

}

//The output compate interrupt handler
//We set up the timer in such a way that
//this ISR is called exactly at 1ms interval
ISR(TIMER1_COMPA_vect)
{
   	clock_millisecond++;
   	if(clock_millisecond==1000)
   	{
    	clock_second++;
      	clock_millisecond=0;
      	if(clock_second==60)
      	{
         	clock_minute++;
         	clock_second=0;
      	}
	  	if(clock_minute==60)
	  	{
	  		clock_hour++;
			clock_minute=0;
		}
   	}
}