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

Aim:

To implement code for “Measuring distance of an object using ultrasonic distance sensor (HC-SR04).

Objective:

• Measuring the distance of an object using Ultrasonic Distance Sensor (HC-SR04)
• Usage of Input Capture Mode

Highlights:

• Measuring the distance travelled by the wave to the object and gets bounced back from the object to sensor.
• Measuring Pulse width using Input Capture Mode

Deliverables:

• The distance travelled by a wave to the object for which we want to measure the distance using Ultrasonic Distance Sensor (HC-SR04).
• Measuring Pulse width using Input Capture Mode of Timer 1

Code:

#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_command_dir DDRC
#define lcd_data_port PORTD
#define lcd_command_port PORTC
#define EN PC2
#define RW PC3
#define RS PC4

void lcd_command(char);
void lcd_char(char);
void lcd_init(void);
void lcd_string(char*);
void lcd_string_xy (char,char,char*);

void lcd_command (char cmd)
{
lcd_data_port = cmd;
lcd_command_port&=~((1<<RS)|(1<<RW));
lcd_command_port|= (1<<EN);
_delay_ms(1);
lcd_command_port&=~(1<<EN);
_delay_ms(2);

}
void lcd_char(char char_data)
{
lcd_data_port= char_data;
lcd_command_port&=~(1<<RW);
lcd_command_port|=((1<<EN)|(1<<RS));
_delay_ms(1);
lcd_command_port&=~(1<<EN);
_delay_ms(1);
}
void lcd_init(void)
{
lcd_command_dir|= (1<<RS)|(1<<RW)|(1<<EN);
lcd_data_dir = 0xff;

_delay_ms(20);
lcd_command(0x38);
lcd_command(0x0C);
lcd_command(0x06);
lcd_command(0x01);
lcd_command(0x80);
}
void lcd_string(char *str)

int i;
for(i=0;str[i]!=0;i++)
{
lcd_char (str[i]);
}

}
void lcd_string_xy(char row,char pos,char *str)
{
if (row == 1)
lcd_command((pos & 0x0f)|0x80);
else if (row == 2)
lcd_command((pos & 0x0f)|(0xC0));
lcd_string(str);
}
#define trigger_pin PA0
int TimerOverFlow = 0;
ISR(TIMER1_OVF_vect)
{
TimerOverFlow++;
}
int main (void)
{
char string[10];
long count;
double distance;

DDRA = 0x01;
PORTB = 0xff;

lcd_init();
lcd_string_xy(1,0,"ultrasonic");

sei();
TIMSK = (1<< TOIE1);
TCCR1A = 0;

while(1)
{
PORTA |= (1<< trigger_pin);
_delay_ms(10);
PORTA &=(~(1<< trigger_pin));

TCNT1 = 0;
TCCR1B = 0x41;
TIFR = 1<<ICF1;
TIFR = 1<<TOV1;


while ((TIFR & (1<<ICF1)) == 0);
TCNT1 = 0;
TCCR1B = 0x01;
TIFR = 1<<ICF1;
TIFR = 1<<TOV1;
TimerOverFlow = 0;

while ((TIFR & (1<< ICF1))== 0);
count = ICR1 +(65535 * TimerOverFlow);
distance = (double)count/466.47;

dtostrf(distance,2,2,string);
strcat(string,"cm");
lcd_string_xy(2,0,"dist= ");
lcd_string_xy(2,7,string);
_delay_ms(200);
}
}
Program:

Circuit:

• The program is loaded in the Atmega 32 chip.
• LCD pins are connected to the Atmega32 as shown above.
• Osillocope and ultrasonic sensors are connected to view the output.

Output:

• 60.38 cm is the distance of an object obtained.

Result:

Thus the implementation of code for “Measuring distance of an object using ultrasonic distance sensor (HC-SR04) is done.