#ifndef _UART_H_
#define _UART_H_

// Helpful defines
#define uart_buffer r_buffer
#define uart_ready r_ready

// RXC ISR variables								
unsigned char r_index;  // current string index
unsigned char r_buffer[16];	// input string 
unsigned char r_ready;  // flag for receive done
unsigned char r_char;  // current character  

// TX ISR variables			
// Set up a circular buffer to output the strings to
#ifndef TRANSMIT_BUFFER_SIZE
#define TRANSMIT_BUFFER_SIZE 21
#endif

unsigned char t_index;  // current string index
unsigned char t_end; // index of end 
unsigned char t_buffer[TRANSMIT_BUFFER_SIZE];	//output string 
unsigned char t_char;  //current character

// Instruction length
#ifndef INST_LENGTH
#define INST_LENGTH 6
#endif                      
                 
// XMIT output DDR
#ifndef XMIT_DDR
#define XMIT_DDR DDRD.4
#endif

// XMIT output port
#ifndef XMIT_OUT
#define XMIT_OUT PORTD.4
#endif 

// UART receive byte ready interrupt
interrupt [USART_RXC] void uart_rec(void)
{       
	// Set the XMIT line to recieve
	XMIT_OUT = 0;
	
	// Read in a character
	r_char=UDR;
	
	// Add the character to the receive buffer
	r_buffer[r_index++]=r_char;
		
	// If we have received a full instruction
	if (r_index == INST_LENGTH)
    {
		// Set the message ready flag
		r_ready=1;	

		// Turn off the receive interrupt
		UCSRB.7=0;
	}
}

// UART data register empty interrupt
interrupt [USART_DRE] void uart_tx(void)
{                
	// Set the XMIT line to transmit
	XMIT_OUT = 1;
	
	// Read in a char from the buffer
	t_char = t_buffer[t_index];

	// Increase and mod the index, to make this a circular buffer
	t_index = (t_index + 1) % TRANSMIT_BUFFER_SIZE;
                     
	// If we have reached the end of the string
	if (t_index == t_end) 	
	{
		// Turn off the transmit interrupt
		UCSRB.5 = 0;
	}

	// Otherwise write it to the UART
	else UDR = t_char;

	// Set the XMIT line back to receive
	XMIT_OUT = 0;
}

// Function to setup the receive interrupt
void uart_gets_int(void) 
{
	// Reset the variables
	r_ready=0;
	r_index=0;

	// Enable the receive ISR
	UCSRB.7=1;
}


// Function to initialize the UART
void uart_init(unsigned char newBPS)
{
	// Setup the UART registers
	UCSRB = 0x18;
	UBRRL = newBPS;
	
	// Setup the XMIT line
	XMIT_DDR = 1;
}

#endif