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

Calculation (distance in cm) 

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-prescale 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

Code:-

#define F_CPU 8000000UL
#include
#include "avr/interrupt.h"
#include
#include
#include

#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 Trigger_pin PA0 /* Trigger pin */
#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<LCD_Command_Port |= (1<_delay_us(1);
LCD_Command_Port &= ~(1<_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<LCD_Command_Port |= (1<_delay_us(1);
LCD_Command_Port &= ~(1<_delay_ms(1); /* Wait little bit */
}

void LCD_Init (void) /* LCD Initialize function */
{
LCD_Command_Dir |= (1<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 */
}

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<TIFR = 1<

/*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<TIFR = 1<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);
}
}