/*
		Project: Relay Remote Control via PC
		Author : Sasa Karanovic (sale@mrdnise.com)

*/

#define F_CPU	8000000UL
#define BAUD	4800
#define MYUBBR	(((F_CPU/16)/BAUD)-1)
#define SIGNAL_LED	PB4
#define RELAY_PIN	PB3

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

/* Prototypes */
void InitUART (unsigned char baudrate);
unsigned char ReceiveByte (void);
void TransmitByte (unsigned char data);


void init() {
	DDRB = 0xFF;
	PORTB = 0x00;
}
/* --------------------------------------------------------------
 Main - program that receives a character then transmits back the next character.  
An example would be if you send in an A, the chip will return a B
---------------------------------------------------------------- */

unsigned char data, status;

int main (void)
{
  init();
  InitUART (MYUBBR);     /* Set the baudrate to 4800 at 8MHz */
  while (1)
    {
		data = ReceiveByte();
		
		if(data != 0x00) {
			if(data == 0x99) {
				PORTB |= (1<<SIGNAL_LED);
				PORTB |= (1<<RELAY_PIN);
				status = 0x55;
				TransmitByte(status);
			}
			else if (data == 0x11) {
				PORTB &= ~(1<<RELAY_PIN);
				PORTB &= ~(1<<SIGNAL_LED);
				status = 0x49;
				TransmitByte (status);
			}
			else if (data == 0x22) {
				TransmitByte(status);
			}
			else {
				TransmitByte(data);
				TransmitByte (0x53);
			}
			data = 0x00;
			_delay_ms(500);
		}			
      
    }
}

/* Initialize UART */
void
InitUART (unsigned char baudrate)
{
  /* Set the baud rate */
  UBRRL = baudrate;

  /* Enable UART receiver and transmitter */
  UCSRB = (1 << RXEN) | (1 << TXEN);

  /* set to 8 data bits, 1 stop bit */
  UCSRC = (1 << UCSZ1) | (1 << UCSZ0);

}

/* Read and write functions */
unsigned char
ReceiveByte (void)
{
  /* Wait for incomming data */
  while (!(UCSRA & (1 << RXC)));

  /* Return the data */
  return UDR;
}

void
TransmitByte (unsigned char data)
{
  /* Wait for empty transmit buffer */
  while (!(UCSRA & (1 << UDRE)));

  /* Start transmittion */
  UDR = data;
}