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

#include <avr/io.h>         // Including AVR input/output library             
#define F_CPU 16000000ul            // define CPU frequency 
#include <util/delay.h>                 // Including AVR time (delay) Library
#include <avr/interrupt.h>          // Including AVR interrupt library
#include <string.h> // Including string Library
#include <stdlib.h> // Including Standard Library


#define lcd_data_dir DDRD           //define lcd_data_dir as PORT-D data register 
#define lcd_command_dir DDRC              //define lcd_command_dir as PORT-C data register
#define lcd_data_port PORTD               //define lcd_data_port as write PORT-D
#define lcd_command_port PORTC                 //define lcd_command_port as write PORT-C
#define EN PC2               //define enable pin 
#define RW PC3              //define read/write pin
#define RS PC4                        //define register select pin

void lcd_command(char);                     //This function is for using LCD in command mode
void lcd_char(char);                      //This function is to use LCD in data mode
void lcd_init(void);                   //LCD initialize function
void lcd_string(char*);                     //This function  is for sending string to LCD
void lcd_string_xy (char,char,char*);                 //This function is for selection of row position

void lcd_command (char cmd)                  
{
	lcd_data_port = cmd;                           
	lcd_command_port&=~((1<<RS)|(1<<RW));              //make RS low and RW low
	lcd_command_port|= (1<<EN);                     //high to low transition on EN PIN of LCD to use it in Command mode
	_delay_ms(1);                        //delay
	lcd_command_port&=~(1<<EN);                    //clear bit
	_delay_ms(2);                        //delay 
}

void lcd_char(char char_data)                       
{
	lcd_data_port= char_data;             // char_data is coming from string function        
	lcd_command_port&=~(1<<RW);                  //make RW low(write)
	lcd_command_port|=((1<<EN)|(1<<RS));           //make Rs high to use LCD in data mode and EN high
	_delay_ms(1);                                             //delay
	lcd_command_port&=~(1<<EN);                     //clear bit --> EN 
	_delay_ms(1);                                   //delay
}

void lcd_init(void)                                
{
	lcd_command_dir|= (1<<RS)|(1<<RW)|(1<<EN);                   
	lcd_data_dir = 0xff;                       //Making PORT-D as output

	_delay_ms(20);                       //wait
	lcd_command(0x38);              //16x2 LCD 8 bit
	lcd_command(0x0C);               //display On
	lcd_command(0x06);              //auto increment cursor
	lcd_command(0x01);                  //clear LCD screen
	lcd_command(0x80);             //Force cursor to begin 1st line
}

void lcd_string(char *str)                 
{
	int i;                                //variable declaration
	for(i=0;str[i]!=0;i++)                 //sending each char string till null
	{
		lcd_char (str[i]);                        //sending full string to lcd_char function
	}
}

void lcd_string_xy(char row,char pos,char *str)                      
{
	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);                                 //calling lcd_string function
}

#define trigger_pin PA0                    //trigger pin --> A0
int TimerOverFlow = 0;                     //variable declaration

ISR(TIMER1_OVF_vect)
{
	TimerOverFlow++;                        //increment timer overflow count
}

int main (void)                         //main function
{
	char string[10];                       //string declaration
	long count;                                  //variable declaration
	double distance;                       //variable declaration

	DDRA = 0x01;                      //make trigger pin as output
	PORTB = 0xff;                                         //pull-up resister turn on

	lcd_init();                                            //function called for LCD initialization
	lcd_string_xy(1,0,"ultrasonic");            //function called

	sei();                              //enabling interrupts
	TIMSK = (1<< TOIE1);                 //enable timer 1 overflow interrupt
	TCCR1A = 0;                           //set all bit to zero normal position (Control Register A)

	while(1)
	{
		PORTA |= (1<< trigger_pin);                 // sending a plus to trigger pin 
		_delay_ms(10);                                 // for 10msec. 
		PORTA &=(~(1<< trigger_pin));          //clear bit

		TCNT1 = 0;                      //clear timer counter
		TCCR1B = 0x41;                //capture on rising edge,no pre scaler
		TIFR = 1<<ICF1;               //Input capture bit of TIFR register 
		TIFR = 1<<TOV1;                  //timer overflow flag bit of TIFR register


		while ((TIFR & (1<<ICF1)) == 0);             //checking ICF1 status till it get 0 
		TCNT1 = 0;                         //clear timer counter
		TCCR1B = 0x01;                    //no prescaler
		TIFR = 1<<ICF1;                    //clear ICP flag
		TIFR = 1<<TOV1;                          //clear timer overflow flag
		TimerOverFlow = 0;                    //clear timer overflow count

		while ((TIFR & (1<< ICF1))== 0);                //checking ICF1 status till it get 0      
		count = ICR1 +(65535 * TimerOverFlow);              //take count
		distance = (double)count/466.47;                  //calculating distance

		dtostrf(distance,2,2,string);                //distance to string
		strcat(string,"cm");                      //string concatenate after string 1 get null this will execute 
		lcd_string_xy(2,0,"dist= ");                   // Printing
		lcd_string_xy(2,7,string);              //Print distance
		_delay_ms(200);                            //delay
	}
}