Wrapper for UART-driver of Atmel for Xmega. More...

#include <avr/io.h>
#include <math.h>
#include "avr_compiler.h"
#include "usart_driver.h"
#include "uart.h"

Functions
uint16_t	uart_getc (USART_data_t *uart)
	Get a byte from the circular receive buffer. More...

void	uart_putc (USART_data_t *uart, uint8_t data)
	Write a byte to the circular transmit buffer. More...

void	uart_puts (USART_data_t uart, char s)
	Write a string to the circulair transmit buffer. More...

void	set_usart_txrx_direction (USART_t *usart)
	Set direction for the transmit and receive pin. More...

uint16_t	calc_bsel (uint32_t f_cpu, uint32_t baud, int8_t scale, uint8_t clk2x)
	Calculates the baud rate value BSEL. More...

int8_t	calc_bscale (uint32_t f_cpu, uint32_t baud, uint8_t clk2x)
	Determines the scale factor BSCALE. More...

void	init_uart (USART_data_t uart, USART_t usart, uint32_t f_cpu, uint32_t baud, uint8_t clk2x)
	Initializes the UART. More...

void	init_uart_levels (USART_data_t uart, USART_t usart, uint32_t f_cpu, uint32_t baud, uint8_t clk2x, USART_RXCINTLVL_t rxcIntLevel, USART_DREINTLVL_t dreIntLevel)
	Initializes the UART. More...

Detailed Description

Wrapper for UART-driver of Atmel for Xmega.

Author: Wim Dolman (w.e.dolman@hva.nl)

Date: 11-12-2015

Version: 1.2

The files uart.c and uart.h uses the UART-driver uart_driver.c and uart_driver.h from Atmel, see http://www.atmel.com/Images/doc8049.pdf and http://www.atmel.com/Images/AVR1307.zip.

It is a kind of wrapper with the same style as the UART-drivers from Peter Fleury (http://jump.to/fleury) for the ATmega.

For every buffered UART we need two Interrupt Service Routine: one for receiving and one for transmitting For each UART there is a condition. If the condition is true the two ISR's will be compiled, else they will be skipped. The condition for UART uart_id depends on a macro ENABLE_UART_uart_id

To use, for example, UARTC1 define in the code just before including uart.h a macro ENABLE_UART_C1:

   #define ENABLE_UART_C1 1
   #include <uart.h>

Note: An AVR-project can use multiple UART's. One shoud take care that in different source files there are no multiple ENABLE_UART_uart_id definitions for the same UART.

Function Documentation

int8_t calc_bscale	(	uint32_t	f_cpu,
		uint32_t	baud,
		uint8_t	clk2x
	)

Determines the scale factor BSCALE.

Parameters

f_cpu	system clock (F_CPU)
baud	desired baud rate
clk2x	clock speed double (1 for double, 0 for no double)

It determines the scale factor BSCALE from the system clock, the baud rate, and a boolean for clock doubling.

Returns: the scale factor BSCALE

uint16_t calc_bsel	(	uint32_t	f_cpu,
		uint32_t	baud,
		int8_t	scale,
		uint8_t	clk2x
	)

Calculates the baud rate value BSEL.

Parameters

f_cpu	system clock (F_CPU)
baud	desired baud rate
scale	scale factor (BSCALE)
clk2x	clock speed double (1 for double, 0 for no double)

It calculates the baud selection value BSEL from the system clock, the baud rate, the scale factor and a boolean for clock doubling.

The formula to calculate BSEL is:

$\begin{eqnarray*} \mbox{BSCALE}>=0\quad &:& \quad \mbox{BSEL} = \frac{f_{\mbox{cpu}}}{N\ 2^{\mbox{BSCALE}}\ f_{\mbox{baud}}} - 1 \\[3pt] \mbox{BSCALE}<0\quad &:& \quad \mbox{BSEL} = \frac{1}{2^{\mbox{BSCALE}}}\ \left( \frac{f_{\mbox{cpu}}}{N\ f_{\mbox{baud}}} - 1 \right) \end{eqnarray*}$

N is a factor which is 16 with no clock doubling and 8 with clock doubling

Returns: the calculated BSEL

void init_uart	(	USART_data_t *	uart,
		USART_t *	usart,
		uint32_t	f_cpu,
		uint32_t	baud,
		uint8_t	clk2x
	)

Initializes the UART.

Parameters

uart	pointer to a UART datastructure with buffers
usart	pointer to a UART datastructure
f_cpu	system clock (F_CPU)
baud	desired baud rate
clk2x	clock speed double (1 for double, 0 for no double)

It calculates the scale factor BSCALE and the baud selection value BSEL. It selects what USART module to use and it initializes receive and transmit buffer. It initializes the USART module and sets the direction of TXD and RXD pin. The interrupt levels of the DRE interrupt function and the RXC interrupt function are both set to a low level.

Returns: void

void init_uart_levels	(	USART_data_t *	uart,
		USART_t *	usart,
		uint32_t	f_cpu,
		uint32_t	baud,
		uint8_t	clk2x,
		USART_RXCINTLVL_t	rxcIntLevel,
		USART_DREINTLVL_t	dreIntLevel
	)

Initializes the UART.

Parameters

uart	pointer to a UART datastructure with buffers
usart	pointer to a UART datastructure (UART module)
f_cpu	system clock (F_CPU)
baud	desired baud rate
clk2x	clock speed double (1 for double, 0 for no double)
rxcIntLevel	RXC interrupt level
dreIntLevel	DRE interrupt level

It calculates the scale factor BSCALE and the baud selection value BSEL. It selects what USART module to use and it initializes receive and transmit buffer. It initializes the USART module and sets the direction of TXD and RXD pin. The interrupt level of the DRE interrupt function and the RXC interrupt function are set to dreIntLevel and rxcIntLevel.

Returns: void

void set_usart_txrx_direction ( USART_t * usart )

Set direction for the transmit and receive pin.

Parameters

usart pointer to UART datastructure (UART module)

Returns: void

uint16_t uart_getc ( USART_data_t * uart )

Get a byte from the circular receive buffer.

Parameters

uart	pointer to UART datastructure with buffers

Returns: received byte from circulair buffer (low byte) or UART_NO_DATA if buffer is empty

void uart_putc	(	USART_data_t *	uart,
		uint8_t	data
	)

Write a byte to the circular transmit buffer.

Parameters

uart	pointer to UART datastructure with buffers
data	byte to be written

Returns: void

void uart_puts	(	USART_data_t *	uart,
		char *	s
	)

Write a string to the circulair transmit buffer.

Parameters

uart	pointer to UART datastructure with buffers
s	pointer to string to be written

Returns: void

Functions

Detailed Description

Function Documentation