Driver for Ultrasonic HC–SR04 Sensor.

HC–SR04.c

//#########################################################################
//
// This is free software driver for Ultrasonic HC–SR04 Sensor. software
// is written for uniHack Vision Plus Team. Driver has two methods to
// transmit information from sensor: Equalizer on board display and USART.
//
// Copyright (c) 2014 uniHack Vision Plus TeaM
// Web: http://off-sec.com/ ; E-Mail: kala0x13@gmail.com
//
// This program is free software; you can redistribute it and/or modify
// it under the terms of the GNU General Public License version 3, or 
// (at your option) any later version; incorporated herein by reference.
//
//#########################################################################

#include <avr/io.h>
#include <util/delay.h>
#include <avr/interrupt.h>
#include <avr/sleep.h>
#include <stdio.h>
#include <stdint.h>

#define DD_HCRS04_Trig_Out  DDRD |=  (1 << 4);		// Test
#define DD_HCRS04_Trig_In   DDRD &= ~(1 << 4);		// Test
#define DD_HCRS04_Echo_Out  DDRD |=  (1 << 5);		// Test
#define DD_HCRS04_Echo_In   DDRD &= ~(1 << 5);		// Test

#define HCRS04_Trig_1		PORTD |=  (1 << 4);	// Test
#define HCRS04_Trig_0		PORTD &= ~(1 << 4);	// Test

#define USART_Wait_For_Free while(USART_Busy){};
#define BAUDRATE	38400				// Set desired baud rate
#define UBRRVAL		((8000000/(BAUDRATE*16UL))-1) 	// Calculate UBRR value

char USART_buffer[128];
unsigned char USART_Positone=0;
unsigned char USART_Busy=0;

void USART_Init();
void USART_Transmit();

//#########################################################################

union {   
	unsigned long _long;
	unsigned short _short;
	unsigned char  _char[4];
} MyVel;

union {
	unsigned long _a1;
	unsigned char  _a4[4];

} All;

int main(void) {

	DDRA = 0xff;
	DDRB = 0xff;
	DDRC = 0xff;

	DD_HCRS04_Trig_Out;
	DD_HCRS04_Echo_In;

	char x1 = 0;
	USART_Init();

	while (1) {

		HCRS04_Trig_1;
		_delay_ms(200);
		HCRS04_Trig_0;
		x1 = PIND & 0b00100000;

		if (x1==0) {

			while (1) {
				x1 = PIND & 0b00100000;
				if (x1!=0) break;
			}

			MyVel._long =  0; PORTA = 0; PORTB = 0; PORTC = 0;

			while (1) {
				MyVel._long++;
				x1 = PIND & 0b00100000;
				if (x1==0) break;
			}

			USART_Wait_For_Free;
			sprintf(USART_buffer,"Distance is: %lu\n\r", MyVel._long);
			USART_Transmit();

			unsigned char i;
			unsigned long st = 325;
			All._a1 = 1;

			for (i = 0; i <= 24; i++) {
					if (st < MyVel._long) {
						st += 325;
						All._a1 = All._a1 << 1;
						All._a1+=1;
					}
			}

			PORTA = All._a4[0];
			PORTB = All._a4[1];
			PORTC = All._a4[2];

			_delay_ms(8);

		} else {
			_delay_ms(25);
		}
	}
}

//#########################################################################

void USART_Init()
{
	UBRR0L= UBRRVAL;		//	Set baud rate, low byte
	UBRR0H=(UBRRVAL>>8);		//	Set baud rate, high byte

	UCSR0C = (0<<UMSEL0)|		//
	    	(0<<UPM01) |		//
	    	(0<<UPM00) |		//
		(0<<USBS0) |		//
		(1<<UCSZ01)|		//
		(1<<UCSZ00)|		//
		(0<<UCPOL0);		//
	UCSR0B = (0<<RXEN)|		//	Enable USART Receiver
		(1<<TXEN)  |		//	Enable USART Transmitter
		(0<<RXCIE) |		//	Enable USART Interrupt on receive complete
		(1<<TXCIE);
	sei();
}

void USART_Transmit() {
	USART_Positone = 0 ;
	if (USART_buffer[USART_Positone]!=0) {
		USART_Busy = 1 ;
		UDR0=USART_buffer[USART_Positone];
	} else {
		USART_Busy = 0 ;
	}
}

ISR(USART0_TX_vect) {
	USART_Positone ++;
	if (USART_buffer[USART_Positone]!=0) {
		UDR0=USART_buffer[USART_Positone];
	} else {
		USART_Busy = 0;
	}
}