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

#include <avr/io.h> //avr header file
#define F_CPU 16000000ul //f_cpu defined
#include <util/delay.h> //delay header file
#include <avr/interrupt.h> //interrupt header file
#include <string.h> // string header file
#include <stdlib.h> // standard library header file

#define lcd_data_dir DDRD // define lcd data port direaction
#define lcd_command_dir DDRC // define lcd command port direaction
#define lcd_data_port PORTD // define lcd data port
#define lcd_command_port PORTC // define lcd data port
#define EN PC2 // define enable
#define RW PC3 // define read/write
#define RS PC4 // define register select

void lcd_command(char); // lcd command write function
void lcd_char(char); // lcd data write function
void lcd_init(void); // lcd initialization function
void lcd_string(char*); // send string to LCD
void lcd_string_xy (char,char,char*); // send row position

void lcd_command (char cmd) // lcd command write function
{
lcd_data_port = cmd; // write command to lcd data port
lcd_command_port&=~((1<<RS)|(1<<RW)); // make RS low and RW low
lcd_command_port|= (1<<EN); // high high to low transition
_delay_ms(1); // delay 1ms
lcd_command_port&=~(1<<EN);
_delay_ms(2);

}
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 and high to low transition
_delay_ms(1);
lcd_command_port&=~(1<<EN);
_delay_ms(1);
}
void lcd_init(void) // lcd initialization function
{
lcd_command_dir|= (1<<RS)|(1<<RW)|(1<<EN); // lcd command port direaction as output
lcd_data_dir = 0xff; // make lcd data port direation as output

_delay_ms(20); // wait
lcd_command(0x38); // 16x2 lcd 8 bit
lcd_command(0x0C); // display On
lcd_command(0x06); // auto increament cursor
lcd_command(0x01); // clear lcd command
lcd_command(0x80); // 8 bit is the line and 0 is the 0th position
}
void lcd_string(char *str) // send string to lcd function
{
int i;
for(i=0;str[i]!=0;i++) // sending each char string till 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);
else if (row == 2)
lcd_command((pos & 0x0f)|(0xC0));
lcd_string(str); // call lcd string function
}
#define trigger_pin PA0 // trigger pin
int TimerOverFlow = 0;
ISR(TIMER1_OVF_vect)
{
TimerOverFlow++; // increament timer overflow count
}
int main (void)
{
char string[10];
long count;
double distance;

DDRA = 0x01; // make trigger pin as output
PORTB = 0xff; // pull up turn on

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

sei(); // enable global interrupt
TIMSK = (1<< TOIE1); // enable timer 1 overflow interrupt
TCCR1A = 0; // set all bit to zero normal position

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

TCNT1 = 0; // clear timer counter
TCCR1B = 0x41; // capture on rising edge, no pre scala
TIFR = 1<<ICF1; // clear ICP flag
TIFR = 1<<TOV1; // clear timer overflow flag


while ((TIFR & (1<<ICF1)) == 0); // wait for raising edge
TCNT1 = 0; // clear time counter
TCCR1B = 0x01; // capture on falling edge no prescalar
TIFR = 1<<ICF1; // clear ICP 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
distance = (double)count/466.47;

dtostrf(distance,2,2,string); // distance to string
strcat(string,"cm"); // count unit
lcd_string_xy(2,0,"dist= ");
lcd_string_xy(2,7,string); // print distance
_delay_ms(200);
}
}