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

code:

#include <avr/io.h>
#define F_CPU 16000000L
#include <util/delay.h>
#define rs_high PORTD |=(1<<0);//DEFINE BIT FOR RS_HIGH
#define rs_low PORTD &=~(1<<0);//DEFINE BIT FOR RS_LOW
#define en_high PORTD |= (1<<2);//DEFINE BIT FOR EN_HIGH
#define en_low PORTD &=~(1<<2);//DEFINE BIT FOR EN_LOW
#define rw_high PORTD |= (1<<1);
#define rw_low PORTD &= ~(1<<1);
#define US_ERROR		-1     
#define	US_NO_OBSTACLE	-2
#define US_PORT PORTC          
#define	US_PIN	PINC          
#define US_DDR 	DDRC           
int distance, previous_distance;

void lcd_cmd(unsigned char cmd)//LCD_COMMAND FUNCTION
{
	PORTB = cmd;
	rs_low;
	rw_high;
	en_high;
	_delay_ms(1);
	en_low;
}
void lcd_data(unsigned char data)//LCD DATA FUNCTION
{
	PORTB = data;
	rw_low;
	rs_high;
	en_high;
	_delay_ms(1);
	en_low;
}
void lcd_init()//LCD INITILIAZATION
{
	rw_high;
	rs_high;
	en_high;
	PORTB = 0xff;
	lcd_cmd(0x38);
	_delay_ms(5);
	lcd_cmd(0x02);
	_delay_ms(5);
	lcd_cmd(0x01);
	_delay_ms(5);
	lcd_cmd(0x0c);
	_delay_ms(5);
	lcd_cmd(0x06);
	_delay_ms(5);
	lcd_cmd(0x80);
	_delay_ms(5);
}
void cursorpos(char x,char y)//CURSOR POSITION FUNCTION
{
	if((x<1 || x>2)||(y<1 || y>16))
	{
		x=1;
		y=1;
	}
	if (x==1)
	{
		lcd_cmd(0x7F+y);
	}
	else
	{
		lcd_cmd(0xBF+y);
	}
}
void lcd_out(char a, char b,char *str)//LCD OUT FUNCTION
{
	cursorpos(a,b);
	while(*str)
	{
		lcd_data(*str);
		str++;
	}
}
void lcd_clear()
{
	lcd_cmd (0x01);   // this line clears the LCD screen
	_delay_ms(2);         // waits for two milliseconds
	lcd_cmd (0x80);   // this line sets the cursor to the row 1 column 1
}
void HCSR04Init()
{
	// we're setting the trigger pin as output as it will generate ultrasonic sound wave
	US_DDR|=(1<<US_TRIG_POS);
}
void HCSR04Trigger()
{   
	US_PORT|=(1<<US_TRIG_POS);	//high
	_delay_us(15);				//wait 15uS
	US_PORT&=~(1<<US_TRIG_POS);	//low
}
uint16_t GetPulseWidth()
{

	for(i=0;i<600000;i++)
	{
		if(!(US_PIN & (1<<US_ECHO_POS)))
		continue;	//Line is still low, so wait
		else
		break;		
	}
	if(i==600000)
	return US_ERROR;	
	
	TCCR1A=0X00;
	TCCR1B=(1<<CS11);
	TCNT1=0x00;			
	for(i=0;i<600000;i++)               s
	{
		if(US_PIN & (1<<US_ECHO_POS))
		{
			if(TCNT1 > 60000) break; else continue;  
		}
		else
		break;
	}
	if(i==600000)
	return US_NO_OBSTACLE;	
	result=TCNT1;          
	TCCR1B=0x00;
	if(result > 60000)
	return US_NO_OBSTACLE;	
	else
	return (result>>1);
}
int main()
{
	lcd_init();          
	char numberString[4];   
	while(1) {
		uint16_t r;
		_delay_ms(100);	
		HCSR04Init();                                              
		while(1)
		{
			
			HCSR04Trigger();              
			r=GetPulseWidth();            
			if(r==US_ERROR)                
			
			{
				cursorpos(1, 1);     
				char j[10] = "Error!";
				lcd_out(1,1,&j);
			}
			else
			{
				distance=(r*0.034/2.0);	
				char f[15]= "Distance = ";
				lcd_out(1,0,&f);
				itoa(distance, numberString, 10);   
				lcd_out(2,4,numberString);
				char h[6] = " cm";
				lcd_out(2,10,&h);
				previous_distance = distance;
				_delay_ms(30);
			}
		}
		
	}
}

Expected Outcomes:

The students will get the Knowledge on Ultrasonic sensor (HC-SR04)
 to measure the distance travelled by wave to the object,
 the hardware connection of Atmega328p and HC-SR04 and how to use
 input capture mode of Timer1