#define F_CPU 8000000UL
#define 	DTOSTR_ALWAYS_SIGN   0x01 // put '+' or ' ' for positives 
#define 	DTOSTR_PLUS_SIGN     0x02 // put '+' rather than ' ' 
#define 	DTOSTR_UPPERCASE     0x04 // put 'E' rather 'e' 
#define 	EXIT_SUCCESS   0
#define 	EXIT_FAILURE   1

#include <avr/io.h>           /* Include AVR std. library file */
#include <util/delay.h>         /* Include inbuilt defined Delay header file */
#include <avr/interrupt.h>

#define RS PB3              /* Define Register Select (data reg./command reg.) signal pin */
#define EN PB2              /* Define Enable signal pin */
volatile int count =0;
volatile unsigned int mode = 0b00000000;

void lcd_sending_command( unsigned char cmnd )
{
  PORTB = (cmnd & 0xF0); /* sending upper nibble */
  PORTB &= ~ (1<<RS);       /* RS=0, command reg. */
  PORTB |= (1<<EN);       /* Enable pulse */
  _delay_us(1);
  PORTB &= ~ (1<<EN);
  PORTB = (cmnd << 4);  /* sending lower nibble */
  PORTB |= (1<<EN);
  _delay_us(1);
  PORTB &= ~ (1<<EN);
  _delay_ms(2);
}


void lcd_sending_data( unsigned char data )
{
  PORTB =  (data & 0xF0); /* sending upper nibble */
  PORTB |= (1<<RS);       /* RS=1, data reg. */
  PORTB|= (1<<EN);
  _delay_us(1);
  PORTB &= ~ (1<<EN);
  PORTB = (data << 4); /* sending lower nibble */
  PORTB |= (1<<RS);
  PORTB |= (1<<EN);
  _delay_us(1);
  PORTB &= ~ (1<<EN);
  _delay_ms(2);
}


void lcd_initialization (void)          /* LCD Initialize function */
{
  DDRB = 0xFF;            /* Make LCD command port direction as o/p */
  _delay_ms(20);            /* LCD Power ON delay always >15ms */
  lcd_sending_command(0x33);      /* Ensures display is in 8-bit mode */
  lcd_sending_command(0x32);        /* send for 4 bit initialization of LCD  */
  lcd_sending_command(0x28);          /* Use 2 line and initialize 5*7 matrix in (4-bit mode)*/
  lcd_sending_command(0x0f);          /* Display on, cursor on and blink cursor*/
  lcd_sending_command(0x01);          /* Clear display screen*/
  lcd_sending_command(0x06);          /* Clear display screen*/
  lcd_sending_command(0x02);          /* Clear display screen*/
  _delay_ms(2);

}


void lcd_display_string (char *str)       /* Send string to LCD function */
{
  int i;
  for(i=0;str[i]!=0;i++)        /* Send each char of string till the NULL */
  {
    lcd_sending_data (str[i]);
  }
}

void lcd_display_int(int LCD_number)
{
    char buffer_LCD[10];
    itoa(LCD_number, buffer_LCD, 10);
    lcd_display_string(buffer_LCD);
}

void lcd_display_float(float LCD_number)
{
	char buffer_LCD[13];
	dtostrf(LCD_number, 5, 3, buffer_LCD);
	lcd_display_string(buffer_LCD);
}



void int5_init(void)

{
   // Make sure you have connected a SW between PD1 (External Interrupt) and GND.
   cli();                 // Clear all the interrupts
   PORTE |= (1 << PE3);   // External SW PullUp
   DDRE &= ~(1 << PE3);   // External Interrupt Sensing Port(PE3) Input Port
   EICRB |= (1<<ISC50);   // External Interrupt 5, Falling Edge Asynchronously Interrupt
   EIMSK |= (1 << INT5);;   // External Interrupt 5 enable
   sei();

}

void T05Delay(void)
{
	TCNT1 = 12500;					  //  TCNT1= for delay of 0.1 seconds
	TCCR1B |=  (1<<CS11);     //  Scale down the timer frequency to 8MHz/256
	while ((TIFR1 & (1<<TOV1))==0);  // wait for TF1 to roll over
	TCCR1B = 0;						    //  Stop Timer
	TIFR1 |=(1<<ICF1)|(1<<OCF1C)|(1<<OCF1B)|(1<<OCF1A)|(1<<TOV1);
}



int main()
{
  int i;
  count = 0;
  lcd_initialization();                 // Initialization of LCD
  int5_init();                    // Initialization of INT5 Interrupt
  lcd_sending_command(0x01);            // Clear display
  lcd_sending_command(0x80);
  lcd_display_string("Press START key");
  while(1) {
  }

}

ISR (INT5_vect, ISR_NOBLOCK)
{
  sei();
  int5_init();
  mode = ~mode;
  lcd_sending_command(0x01);            // Clear display
  lcd_sending_command(0x80);
  lcd_display_string("Timing Started");
  if (mode != 0b00000000) count=0;
  lcd_sending_command(0x00);
  while (mode != 0b00000000) {
    T05Delay();
    count++;
    lcd_sending_command(0xc0);
    lcd_display_float((float)count*0.1);
    lcd_display_string(" sec");
  } 
	EIMSK |= (1 << INT5);     // External Interrupt 0 enable
}