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

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#define F_CPU 8000000UL
#include <avr/io.h>
#include <avr/interrupt.h>
#include <util/delay.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));                   // Make RS LOW (command reg.), RW LOW (Write) 
	LCD_Command_Port |= (1<<EN);                              // High to Low transition on EN (Enable) 
	_delay_us(1);
	LCD_Command_Port &= ~(1<<EN);
	_delay_ms(3);                                             // 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);                             // Make RW LOW (Write) 
	LCD_Command_Port |= (1<<EN)|(1<<RS);                      // Make RS HIGH (data reg.) and High to Low transition on EN (Enable) 
	_delay_us(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);               // Make LCD command port direction as o/p 
	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_us(10);
		PORTA &= (~(1 << Trigger_pin));

		TCNT1 = 0;                                             // Clear Timer counter 
		TCCR1B = 0x41;                                         // Capture on rising edge, No prescaler
		TIFR = 1<<ICF1;                                        // Clear ICP flag (Input Capture flag) 
		TIFR = 1<<TOV1;                                        // Clear Timer Overflow flag 

		/*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;                                         // Clear ICP flag (Input Capture flag)
		TIFR = 1<<TOV1;                                         // Clear Timer Overflow flag 
		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 i.e.cm 
		LCD_String_xy(2, 0, "Dist = ");
		LCD_String_xy(2, 7, string);                             // Print distance 
		_delay_ms(200);
	}
}