// USART transmit and receive ring buffer. 
typedef struct USART_Buffer
{
	// Receive buffer. 
	volatile uint8_t RX[USART_RX_BUFFER_SIZE];
	// Transmit buffer. 
	volatile uint8_t TX[USART_TX_BUFFER_SIZE];
	// Receive buffer head. 
	volatile uint8_t RX_Head;
	// Receive buffer tail. 
	volatile uint8_t RX_Tail;
	// Transmit buffer head. 
	volatile uint8_t TX_Head;
	// Transmit buffer tail. 
	volatile uint8_t TX_Tail;
} USART_Buffer_t;


/* Struct used when interrupt driven driver is used.
*
*  Struct containing pointer to a usart, a buffer and a location to store Data
*  register interrupt level temporary.
*/
typedef struct Usart_and_buffer
{
	// Pointer to USART module to use.  
	USART_t * usart;
	// Data register empty interrupt level.  
	USART_DREINTLVL_t dreIntLevel;
	// Data buffer. 
	USART_Buffer_t buffer;
} USART_data_t;

#define USART USARTC0
USART_data_t USART_data;