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

PROJECT 2

#include //this header file Includes the AVR I/O definitions
#include //Includes the AVR interrupt definitions.
#define F_CPU 16000000//this Specifies the CPU frequency for the delay functions.
#define FOSC 1843200//this Specifies the oscillator frequency.
#define Baudrate 9600//this Specifies the baud rate for serial communication.
#define UBRR ((FOSC/(16*Baudrate))-1)//this Calculates the value for USART Baud Rate Register (UBRR).
#include // Includes the utility delay functions.
#define TRIGGER_PIN PORTB && 0x02//this Defines the trigger pin as the second bit of PORTB.
#define ECHO_PIN PORTB && 0x01//this Defines the echo pin as the first bit of PORTB.

unsigned int pulse_width = 0;//this variable used to store the pulse width.

void uart_init()
{
    UBRR0H = UBRR << 8;
    UBRR0L = UBRR;
    UCSR0B = (1 << TXEN0) | (1 << RXEN0);//here enabling the transmitter and receiver
    UCSR0C = (1 << UCSZ00) | (1 << UCSZ01);//there registers sets high by which 8 bit data can operate
}

void usart_transmit(unsigned char data){
    while ((UCSR0A && (1 << UDRE0))==0);//when the UDR register gets empty then the UDR register will goinng to receive th data
    
    UDR0 = data;
}

void send_string( char* str)//this function is used for printing any sentence type data and this coding is fixed for printing any char data bit wise
{
    while (*str) {
        usart_transmit(*str);
        str++;
    }
}

void send_number(unsigned int num)//this function is used for printing the integer data by storing the data one by one bit operation
{
    unsigned int n;
    do {
        n=num % 10 + 48;// here used 48 i.e. noting but the ascii value of 0 and that value will going to store in n variable
        num= num/ 10;
        usart_transmit(n);
    } while (num > 0);
    
}

void trigger()// this function coding is fixed when we are using the ultrasonic wave for finding the distance
{
    uart_init();// this is used for giving the baudrate of 9600
    PORTB |=(1 << 1);// this PB1 pin used as triggered pin and this OC1A
    _delay_us(25);// here we must be use delay of at least 15 micro second because if we take less then of 15us then our echo system don't works
    PORTB &= ~(1 << 1);
}

void timer1_init() {
    ACSR &= ~(1 << ACIC);//Analog Comparator Input Capture Enable , this register used because we are receiving the input via potentiometer
    TIFR1 |= (1 << ICF1);//Timer/Counter1, Input Capture Flag, when ever we are using ICP1  pin at that time we need to set this register(PB0 pin).
    TCNT1 = 0;
    TCCR1A = 0;//WGM10, WGM11 sets low here by which we are going to use PWM mode as normal.
    TCCR1B &= ~((1 << WGM12) | (1 << WGM13) | (1 << ICES1));//When the ICES1 bit is written to zero, a falling (negative) edge is used as trigger
    TCCR1B |= (1 << 2);//for using prescaler from 256
    TIMSK1 |= (1 << ICIE1);//for enabling the timer1 interrupt we need to set this register
}

ISR(TIMER1_CAPT_vect)//here we are calling for the timer interrupt for calculating the pulse width
 {
    pulse_width = ((ICR1 - 12) * 10) / 625;
}
void main(void) {
    DDRB |= (1 << TRIGGER_PIN );// here we are making the trigger pin as output pin
    DDRB &= ~(1 << ECHO_PIN );//here we are making the echo pin as a input pin
    
    unsigned int distance= 0;
    
    uart_init();

    while (1) {
        trigger();
        timer1_init();
        sei();// global interrupt enable
        distance = (34*pulse_width)/ 2;// it is simply a formula for calculating the distance according to pulse width
        send_string("Distance ");
        send_number(distance);
        send_string(" cm\r\n");
        _delay_ms(40);
    }
}