Project 2 - Measuring distance of an object using ultrasonic sensor (HC-SR04)

#define F_CPU 8000000UL
#include <avr/io.h>
#include <util/delay.h>
#include <avr/interrupt.h>
#include <string.h>
#include <stdlib.h>


#define LCD_Data_Dir DDRD /* Define LCD data port direction */
#define LCD_Command_Dir DDRC /* Define LCD command port direction register */
#define LCD_Data_Port PORTD /* Define LCD data port */
#define LCD_Command_Port PORTC /* Define LCD data port */
#define EN PC2 /* Define Enable signal pin */
#define RW PC3 /* Define Read/Write signal pin */
#define RS PC4 /* Define Register Select (data reg./command reg.) signal pin */

void LCD_Command (char); /* LCD command write function */
void LCD_Char (char); /* LCD data write function */
void LCD_Init (void); /* LCD Initialize function */
void LCD_String (char*); /* Send string to LCD function */
void LCD_String_xy (char,char,char*); /* Send row, position and string to LCD function */

void LCD_Command (char cmd) /* LCD command write function */
{
	LCD_Data_Port = cmd; /* Write command data to LCD data port */
	LCD_Command_Port &= ~((1<<RS)|(1<<RW));
	LCD_Command_Port |= (1<<EN);
	_delay_ms(1);
	LCD_Command_Port &= ~(1<<EN);
	_delay_ms(2); /* Wait little bit */
}

void LCD_Char (char char_data) /* LCD data write function */
{
	LCD_Data_Port = char_data; /* Write data to LCD data port */
	LCD_Command_Port &= ~(1<<RW);
	LCD_Command_Port |= ((1<<EN)|(1<<RS));
	_delay_ms(1);
	LCD_Command_Port &= ~(1<<EN);
	_delay_ms(1); /* Wait little bit */
}

void LCD_Init (void) /* LCD Initialize function */
{
	LCD_Command_Dir |= (1<<RS)|(1<<RW)|(1<<EN);
	LCD_Data_Dir = 0xFF; /* Make LCD data port direction as o/p */

	_delay_ms(20); /* LCD power up time to get things ready, it should always >15ms */
	LCD_Command (0x38); /* Initialize 16X2 LCD in 8bit mode */
	LCD_Command (0x0C); /* Display ON, Cursor OFF command */
	LCD_Command (0x06); /* Auto Increment cursor */
	LCD_Command (0x01); /* Clear LCD command */
	LCD_Command (0x80); /* 8 is for first line and 0 is for 0th position */
}

void LCD_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_Char (str[i]); /* Call LCD data write */
    }
}

void LCD_String_xy (char row, char pos, char *str) /* Send string to LCD function */
{
   if (row == 1)
       LCD_Command((pos & 0x0F)|0x80); /* Command of first row and required position<16 */
   else if (row == 2)
        LCD_Command((pos & 0x0F)|0xC0); /* Command of Second row and required position<16 */
        LCD_String(str); /* Call LCD string function */
}
#define Trigger_pin PA0 /* Trigger pin */
int TimerOverflow = 0;
ISR(TIMER1_OVF_vect)
{
    TimerOverflow++; /* Increment Timer Overflow count */
}

int main(void)
{
    char string[10];
    long count;
    double distance;
    DDRA = 0x01; /* Make trigger pin as output */
    PORTB = 0xff; /* Turn on Pull-up */

    LCD_Init();
    LCD_String_xy(1, 0, "Ultrasonic");

     sei(); /* Enable global interrupt */
     TIMSK = (1 << TOIE1); /* Enable Timer1 overflow interrupts */
    TCCR1A = 0; /* Set all bit to zero Normal operation */

	while(1)
	{
	/* Give 10us trigger pulse on trig. pin to HC-SR04 */
	PORTA |= (1 << Trigger_pin);
	_delay_ms(10);
	PORTA &= (~(1 << Trigger_pin));

	TCNT1 = 0; /* Clear Timer counter */
	TCCR1B = 0x41; /* Capture on rising edge, No prescaler*/
	TIFR = 1<<ICF1;
	TIFR = 1<<TOV1;
    //TimeOverFlow=0;
	/*Calculate width of Echo by Input Capture (ICP) */

	while ((TIFR & (1 << ICF1)) == 0);/* Wait for rising edge */
	TCNT1 = 0; /* Clear Timer counter */
	TCCR1B = 0x01; /* Capture on falling edge, No prescaler */
	TIFR = 1<<ICF1;
	TIFR = 1<<TOV1;
	TimerOverflow = 0; /* Clear Timer overflow count */

	while ((TIFR & (1 << ICF1)) == 0); /* Wait for falling edge */
	count = ICR1 + (65535 * TimerOverflow); /* Take count */
	/* 8MHz Timer freq, sound speed =343 m/s */
	distance = (double)count / 466.47;

	dtostrf(distance, 2, 2, string);/* distance to string */
	strcat(string, " cm "); /* Concat unit cm */
	LCD_String_xy(2, 0, "Dist = ");
	LCD_String_xy(2, 7, string); /* Print distance */
	_delay_ms(200);
}
}