USART RS485 example with PDC for SAM.

#include <string.h>
#include "asf.h"
#include "stdio_serial.h"
#include "conf_board.h"
#include "conf_clock.h"
#include "conf_example.h"

Macros
#define	ACK_CHAR 0x13
	Character to acknowledge receipt of the sync char. More...

#define	ALL_INTERRUPT_MASK 0xffffffff
	All interrupt mask. More...

#define	BUFFER_SIZE 2000
	Size of the receive buffer and transmit buffer. More...

#define	PDC_BUF_SIZE BUFFER_SIZE
	Size of the buffer. More...

#define	STRING_EOL "\r"

#define	STRING_HEADER

#define	SYNC_CHAR 0x11
	Character to synchronize with the other end. More...

#define	SYS_TICK_FREQ 1000
	System tick frequency in Hz. More...

#define	TIMEOUT (1000)
	Acknowledge time out. More...

Typedefs
typedef enum st_usart_state	usart_state_t
	State of the USART. More...

Enumerations
enum	st_usart_state { INITIALIZED, TRANSMITTING, RECEIVING, RECEIVED, TRANSMITTED }
	State of the USART. More...

Functions
static void	configure_console (void)
	Configure UART for debug message output. More...

static void	configure_systick (void)
	Configure system tick to generate an interrupt every 1ms. More...

static void	configure_usart (void)
	USART RS485 mode configuration. More...

static uint32_t	get_tick_count (void)
	Get the tick count value. More...

int	main (void)
	usart_rs485 Application entry point. More...

void	SysTick_Handler (void)
	Handler for System Tick interrupt. More...

void	USART_Handler (void)
	Handler for USART interrupt. More...

static void	wait (volatile uint32_t ul_ms)
	Wait for some time in ms. More...

Variables
Pdc *	g_p_pdc
	Pointer to PDC register base. More...

pdc_packet_t	g_st_packet
	PDC data packet. More...

volatile usart_state_t	g_state = INITIALIZED
	Global usart state. More...

uint8_t	g_uc_receive_buffer [BUFFER_SIZE]
	Receive buffer. More...

uint8_t	g_uc_transmit_buffer [BUFFER_SIZE]
	Transmit buffer. More...

volatile uint32_t	g_ul_tick_count
	Tick Counter in unit of ms. More...

#define ACK_CHAR 0x13

Character to acknowledge receipt of the sync char.

Referenced by main().

#define ALL_INTERRUPT_MASK 0xffffffff

All interrupt mask.

Referenced by configure_usart().

#define BUFFER_SIZE 2000

Size of the receive buffer and transmit buffer.

Referenced by main().

#define PDC_BUF_SIZE BUFFER_SIZE

Size of the buffer.

Referenced by main().

#define STRING_EOL "\r"

#define STRING_HEADER

Value:

"-- USART RS485 Example --\r\n" \
        "-- "BOARD_NAME" --\r\n" \
        "-- Compiled: "__DATE__" "__TIME__" --"STRING_EOL

Referenced by main().

#define SYNC_CHAR 0x11

Character to synchronize with the other end.

Referenced by main().

#define SYS_TICK_FREQ 1000

System tick frequency in Hz.

Referenced by configure_systick().

#define TIMEOUT (1000)

Acknowledge time out.

Referenced by main().

typedef enum st_usart_state usart_state_t

State of the USART.

enum st_usart_state

State of the USART.

Enumerator
INITIALIZED
TRANSMITTING
RECEIVING
RECEIVED
TRANSMITTED

static void configure_console ( void )

static

Configure UART for debug message output.

References uart_rs232_options::baudrate, CONF_UART, CONF_UART_BAUDRATE, CONF_UART_PARITY, stdio_serial_init(), and sysclk_enable_peripheral_clock().

Referenced by main().

static void configure_systick ( void )

static

Configure system tick to generate an interrupt every 1ms.

References SYS_TICK_FREQ, and sysclk_get_cpu_hz().

Referenced by main().

static void configure_usart ( void )

static

USART RS485 mode configuration.

Configure USART in RS485 mode, asynchronous, 8 bits, 1 stop bit, no parity, 256000 bauds and enable its transmitter and receiver.

References ALL_INTERRUPT_MASK, SAM4L, sysclk_enable_peripheral_clock(), sysclk_get_peripheral_hz(), usart_disable_interrupt(), usart_enable_rx(), usart_enable_tx(), and usart_init_rs485().

static uint32_t get_tick_count ( void )

static

Get the tick count value.

References g_ul_tick_count.

Referenced by main().

int main ( void )

usart_rs485 Application entry point.

Configure USART in RS485 mode. If the application starts earlier, it acts as a receiver. Otherwise, it should be a transmitter.

Returns: Unused (ANSI-C compatibility).

References ACK_CHAR, board_init(), BUFFER_SIZE, configure_console(), configure_systick(), configure_usart(), g_p_pdc, g_state, g_uc_receive_buffer, g_uc_transmit_buffer, get_tick_count(), NULL, PDC_BUF_SIZE, pdc_enable_transfer(), pdc_rx_init(), pdc_tx_init(), pio_set_pin_high(), pio_set_pin_low(), RECEIVED, RECEIVING, STRING_HEADER, SYNC_CHAR, sysclk_init(), TIMEOUT, TRANSMITTING, pdc_packet::ul_addr, pdc_packet::ul_size, usart_disable_rx(), usart_enable_interrupt(), usart_enable_rx(), usart_enable_tx(), usart_get_pdc_base(), usart_is_rx_buf_end(), and wait().

void SysTick_Handler ( void )

Handler for System Tick interrupt.

Process System Tick Event. Increment the ul_ms_ticks counter.

References g_ul_tick_count.

void USART_Handler ( void )

Handler for USART interrupt.

References g_state, RECEIVED, RECEIVING, TRANSMITTED, TRANSMITTING, usart_disable_interrupt(), and usart_get_status().

static void wait ( volatile uint32_t ul_ms )

static

Wait for some time in ms.

References g_ul_tick_count.

Referenced by main().

Pdc* g_p_pdc

Pointer to PDC register base.

pdc_packet_t g_st_packet

PDC data packet.

volatile usart_state_t g_state = INITIALIZED

Global usart state.

Referenced by main(), and USART_Handler().

uint8_t g_uc_receive_buffer[BUFFER_SIZE]

Receive buffer.

Referenced by main().

uint8_t g_uc_transmit_buffer[BUFFER_SIZE]

Initial value:

= "DESCRIPTION of this example: \r\n \
 **************************************************************************\r\n\
 *  This application gives an example of how to use USART in RS485 mode.\r\n\
 *  RS-485 is a standard defining the electrical characteristics of drivers \r\n\
 *  and receivers for use in balanced digital multipoint systems. The standard \r\n\
 *  is published by the ANSI TIA/EIA. \r\n\
 *  \r\n\
 *  This example connects two boards through RS485 interface. One board acts \r\n\
 *  as the transmitter and the other one as the receiver. It is determined by \r\n\
 *  the sequence the two applications started. The earlier started board will \r\n\
 *  act automatically as the receiver due to no acknowledgement received. The \r\n\
 *  receiver will wait until sync character is received. Then it sends the \r\n\
 *  acknowledgement and waits for the full frame sent by the transmitter. \r\n\
 *  At the end of reception, it prints out message through UART interface to \r\n\
 *  assert that the whole process succeeds.\r\n\
 **************************************************************************\r\n\
 END of DESCRIPTION \r\n\
 "

Transmit buffer.

Pure ASCII text.

Referenced by main().

volatile uint32_t g_ul_tick_count

Tick Counter in unit of ms.

Referenced by get_tick_count(), SysTick_Handler(), and wait().

Microchip® Advanced Software Framework

Macros

Typedefs

Enumerations

Functions

Variables