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

*The implementation of code for “Measuring distance of an object using ultrasonic distance sensor (HC-SR04).

*Measuring Pulse width using Input Capture Mode of Timer 1.

CODE:-

#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

}

}

Output:-