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

#include <avr/io.h>
#define F_CPU 16000000ul
#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
#define lcd_data_port PORTD       //define lcd data port
#define lcd_command_port PORTC      // define lcd data port
#define EN PC2                      // define enable 
#define RW PC3                       // define read/write
#define RS PC4                       // define register select

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 dtring to lcd
void lcd_string_xy (char,char,char*);          // send row postion

void lcd_command (char cmd)                    // lcd command write function
{
	lcd_data_port = cmd;                          // write command to lcd data port 
	lcd_command_port&=~((1<<RS)|(1<<RW));                    // make RS low and RW low
	lcd_command_port|= (1<<EN);                         // high to low transition on EN
	_delay_ms(1);
	lcd_command_port&=~(1<<EN);
	_delay_ms(2);                                   // delay provided
	
}
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 and high to low tnasition
	_delay_ms(1);
	lcd_command_port&=~(1<<EN);
	_delay_ms(1);
}
void lcd_init(void)                                //  lcd initialize function
{
	lcd_command_dir|= (1<<RS)|(1<<RW)|(1<<EN);              // lcd command port direction as output
	lcd_data_dir = 0xff;                                     //make lcd data port direction 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 command
	lcd_command(0x80);                     // 8 is the line and 0 is oth position
}
void lcd_string(char *str)             // send string to lcd function
{
	int i;
	for(i=0;str[i]!=0;i++)            // sending each char string till tje 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);
	else if (row == 2)
	lcd_command((pos & 0x0f)|(0xC0));
	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;                         // pull-up turn on
	
	lcd_init();
	lcd_string_xy(1,0,"ultrasonic");
	
	sei();                                // enable global interrupt
	TIMSK = (1<< TOIE1);                 // enable timer 1 overflow interrupt
	TCCR1A = 0;                           // set all bit to zero normal position
	
	while(1)
	{
		PORTA |= (1<< trigger_pin);
		_delay_ms(10);
		PORTA &=(~(1<< trigger_pin));
		
		TCNT1 = 0;                             //clear timer counter
		TCCR1B = 0x41;                          // capture on rising edge,no pre scaler
		TIFR = 1<<ICF1;                           // clear ICP flag
		TIFR = 1<<TOV1;                          // clear timer overflow flag
		
		
		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
		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
		distance = (double)count/466.47;
		
		dtostrf(distance,2,2,string);                      // distance to string
		strcat(string,"cm");                              // count unit 
		lcd_string_xy(2,0,"dist= ");
		lcd_string_xy(2,7,string);                     // print distance 
		_delay_ms(200);
	}
}