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

SOLLUTION:-

Steps of Programming

1. ATmega16 microcontroller needs to transmit at least 10 us trigger pulse to the HC-SR04 Trig Pin.
2. After getting a trigger pulse, HC-SR04 automatically sends eight 40 kHz sound waves and the microcontroller waits for rising edge output at the Echo pin.
3. When the rising edge capture occurs at the Echo pin which is connected to an input of ATmega16, start Timer of ATmega16 and again wait for a falling edge on the Echo pin.
4. As soon as the falling edge is captured at the Echo pin, the microcontroller reads the count of the Timer. This time count is used to calculate the distance to an object.

Calculation (distance in cm) (H1)

Sound velocity = 343.00 m/s = 34300 cm/s

The distance of Object (in cm) = Sound velocity *Timer/2

= 32300*Timer/2

= 17150*Timer

Now, here we have selected an internal 8 MHz oscillator frequency for ATmega16, with No-presale for timer frequency. Then time to execute 1 instruction is 0.125 us.

So, the timer gets incremented after 0.125 us time elapse.

= 17150 x (TIMER value) x 0.125 x 10^-6 cm

= 0.125 x (TIMER value)/58.30 cm

= (TIMER value) / 466.47 cm

/*
* ultrasonicp2.c
*
* Created: 10-04-2022 13:01:31
* Author : SS
*/

#define F_CPU 8000000UL
#include <avr/io.h>
#include <avr/interrupt.h>
#include <util/delay.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 register */
#define LCD_Data_Port PORTD /* Define LCD data port */
#define LCD_Command_Port PORTC /* Define LCD data port */
#define EN PC2 /* Define Enable signal pin */
#define RW PC3 /* Define Read/Write signal pin */
#define RS PC4 /* Define Register Select (data reg./command reg.) signal pin */

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 string to LCD function */
void LCD_String_xy (char,char,char*); /* Send row, position and string to LCD function */

void LCD_Command (char cmd) /* LCD command write function */
{
LCD_Data_Port = cmd; /* Write command data to LCD data port */
LCD_Command_Port &= ~((1<<RS)|(1<<RW)); /* Make RS LOW (command reg.), RW LOW (Write) */
LCD_Command_Port |= (1<<EN); /* High to Low transition on EN (Enable) */
_delay_us(1);
LCD_Command_Port &= ~(1<<EN);
_delay_ms(3); /* Wait little bit */
}

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 (data reg.) and High to Low transition on EN (Enable) */
_delay_us(1);
LCD_Command_Port &= ~(1<<EN);
_delay_ms(1); /* Wait little bit */
}

void LCD_Init (void) /* LCD Initialize function */
{
LCD_Command_Dir |= (1<<RS)|(1<<RW)|(1<<EN); /* Make LCD command port direction as o/p */
LCD_Data_Dir = 0xFF; /* Make LCD data port direction as o/p */

_delay_ms(20); /* LCD power up time to get things ready, it should always >15ms */
LCD_Command (0x38); /* Initialize 16X2 LCD in 8bit mode */
LCD_Command (0x0C); /* Display ON, Cursor OFF command */
LCD_Command (0x06); /* Auto Increment cursor */
LCD_Command (0x01); /* Clear LCD command */
LCD_Command (0x80); /* 8 is for first line and 0 is for 0th position */
}

void LCD_String (char *str) /* Send string to LCD function */
{
int i;
for(i=0;str[i]!=0;i++) /* Send each char of string till the 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); /* 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); /* 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; /* Turn on Pull-up */

LCD_Init();
LCD_String_xy(1, 0, "Ultrasonic");

sei(); /* Enable global interrupt */
TIMSK = (1 << TOIE1); /* Enable Timer1 overflow interrupts */
TCCR1A = 0; /* Set all bit to zero Normal operation */

while(1)
{
/* Give 10us trigger pulse on trig. pin to HC-SR04 */
PORTA |= (1 << Trigger_pin);
_delay_us(10);
PORTA &= (~(1 << Trigger_pin));

TCNT1 = 0; /* Clear Timer counter */
TCCR1B = 0x41; /* Capture on rising edge, No prescaler*/
TIFR = 1<<ICF1; /* Clear ICP flag (Input Capture flag) */
TIFR = 1<<TOV1; /* Clear Timer Overflow flag */

/*Calculate width of Echo by Input Capture (ICP) */

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 (Input Capture 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 */
/* 8MHz Timer freq, sound speed =343 m/s */
distance = (double)count / 466.47;

dtostrf(distance, 2, 2, string);/* distance to string */
strcat(string, " cm "); /* Concat unit i.e.cm */
LCD_String_xy(2, 0, "Dist = ");
LCD_String_xy(2, 7, string); /* Print distance */
_delay_ms(200);
}
}

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