#include <avr/io.h>

#include <string.h>



// This is the arbitrary number that corresponds to baud

// rates. A lookup table for these numbers is found on

// page 168 of the datasheet.

#define BAUD_CONST 12


// Current heading to be sent to the master uC
extern volatile unsigned int current_heading;


/*******************************************************************************

*

*	FUNCTION:		USART_Init()

*

*	PURPOSE:		This function initializes the USART for receiving and

*					transmitting. It sets the baud rate, frame format and

*					enables rx/tx.

*

*	CALLED FROM:	main.c/main()

*

*	PARAMETERS:		Nothing.

*

*	RETURNS:		Nothing.

*

*	COMMENTS:		Nothing.

*

*******************************************************************************/

void USART_Init(void)

{

	// Set the baud rate. [136] 

	UBRRH   =   (unsigned char) (BAUD_CONST >> 8);

	UBRRL   =   (unsigned char) BAUD_CONST;

   

	// Sets the RXEN (receiving) and TXEN (sending) bits in

	// the UCSRB register. [154]

	UCSRB   =   (1 << RXEN)|(1 << TXEN);

   

	// Set frame format: 8 data, 1 stop bit.

	UCSRC   =   (1 << URSEL)|(3 << UCSZ0);

} 



/*******************************************************************************

*

*	FUNCTION:		USART_Transmit()

*

*	PURPOSE:		This function waits for the transmit buffer to be empty and

*					then sends data to it when space is available.

*

*	CALLED FROM:	serial_coms.c/print()

*

*	PARAMETERS:		The data that is to be sent to the transmit buffer when

*					room is available.

*

*	RETURNS:		Nothing.

*

*	COMMENTS:		This is used solely as an internal function to modularize

*					the code. This function sends one character out at a time,

*					with each character being fed via print().

*

*******************************************************************************/

void USART_Transmit(unsigned char data)

{

	// Wait for empty transmit buffer.

	while(!(UCSRA & (1 << UDRE)));

	

	// Put data in buffer/send data. [140]

	UDR	= data;

}



/*******************************************************************************

*

*	FUNCTION:		USART_Receive()

*

*	PURPOSE:		This function waits for data to get to the receiving buffer

*					and then returns that data.

*

*	CALLED FROM:	Anywhere where data is being received from the USART.

*

*	PARAMETERS:		Nothing.

*

*	RETURNS:		Data that is received.

*

*	COMMENTS:		Nothing.

*

*******************************************************************************/

unsigned char USART_Receive(void)

{

	// Wait for data to get here.

	while(!(UCSRA & (1 << RXC)));

	

	// Get/return the data from the buffer.

	return UDR;

}



/*******************************************************************************

*

*	FUNCTION:		print()

*

*	PURPOSE:		This function prepares data to be sent to USART_Transmit

*					for output.

*

*	CALLED FROM:	Anywhere where data is being sent to the USART.

*

*	PARAMETERS:		Nothing.

*

*	RETURNS:		Nothing.

*

*	COMMENTS:		Nothing.

*

*******************************************************************************/

void print(char *text)

{

	int i = 0;

	for(i = 0; i < strlen(text); i++)

	{

		USART_Transmit(text[i]);

	}

}