Demo/AVR_ATMega323_IAR/serial/serial.c

/*
    FreeRTOS V6.0.4 - Copyright (C) 2010 Real Time Engineers Ltd.

    ***************************************************************************
    *                                                                         *
    * If you are:                                                             *
    *                                                                         *
    *    + New to FreeRTOS,                                                   *
    *    + Wanting to learn FreeRTOS or multitasking in general quickly       *
    *    + Looking for basic training,                                        *
    *    + Wanting to improve your FreeRTOS skills and productivity           *
    *                                                                         *
    * then take a look at the FreeRTOS eBook                                  *
    *                                                                         *
    *        "Using the FreeRTOS Real Time Kernel - a Practical Guide"        *
    *                  http://www.FreeRTOS.org/Documentation                  *
    *                                                                         *
    * A pdf reference manual is also available.  Both are usually delivered   *
    * to your inbox within 20 minutes to two hours when purchased between 8am *
    * and 8pm GMT (although please allow up to 24 hours in case of            *
    * exceptional circumstances).  Thank you for your support!                *
    *                                                                         *
    ***************************************************************************

    This file is part of the FreeRTOS distribution.

    FreeRTOS is free software; you can redistribute it and/or modify it under
    the terms of the GNU General Public License (version 2) as published by the
    Free Software Foundation AND MODIFIED BY the FreeRTOS exception.
    ***NOTE*** The exception to the GPL is included to allow you to distribute
    a combined work that includes FreeRTOS without being obliged to provide the
    source code for proprietary components outside of the FreeRTOS kernel.
    FreeRTOS is distributed in the hope that it will be useful, but WITHOUT
    ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
    FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
    more details. You should have received a copy of the GNU General Public 
    License and the FreeRTOS license exception along with FreeRTOS; if not it 
    can be viewed here: http://www.freertos.org/a00114.html and also obtained 
    by writing to Richard Barry, contact details for whom are available on the
    FreeRTOS WEB site.

    1 tab == 4 spaces!

    http://www.FreeRTOS.org - Documentation, latest information, license and
    contact details.

    http://www.SafeRTOS.com - A version that is certified for use in safety
    critical systems.

    http://www.OpenRTOS.com - Commercial support, development, porting,
    licensing and training services.
*/


/* BASIC INTERRUPT DRIVEN SERIAL PORT DRIVER FOR IAR AVR PORT. */


#include <stdlib.h>
#include "FreeRTOS.h"
#include "queue.h"
#include "task.h"
#include "serial.h"

#define serBAUD_DIV_CONSTANT			( ( unsigned long ) 16 )

/* Constants for writing to UCSRB. */
#define serRX_INT_ENABLE				( ( unsigned char ) 0x80 )
#define serRX_ENABLE					( ( unsigned char ) 0x10 )
#define serTX_ENABLE					( ( unsigned char ) 0x08 )
#define serTX_INT_ENABLE				( ( unsigned char ) 0x20 )

/* Constants for writing to UCSRC. */
#define serUCSRC_SELECT					( ( unsigned char ) 0x80 )
#define serEIGHT_DATA_BITS				( ( unsigned char ) 0x06 )

static xQueueHandle xRxedChars;
static xQueueHandle xCharsForTx;

#define vInterruptOn()										\
{															\
	unsigned char ucByte;								\
															\
	ucByte = UCSRB;											\
	ucByte |= serTX_INT_ENABLE;								\
	outb( UCSRB, ucByte );									\
}																				
/*-----------------------------------------------------------*/

#define vInterruptOff()										\
{															\
	unsigned char ucByte;								\
															\
	ucByte = UCSRB;											\
	ucByte &= ~serTX_INT_ENABLE;							\
	outb( UCSRB, ucByte );									\
}
/*-----------------------------------------------------------*/

xComPortHandle xSerialPortInitMinimal( unsigned long ulWantedBaud, unsigned portBASE_TYPE uxQueueLength )
{
unsigned long ulBaudRateCounter;
unsigned char ucByte;

	portENTER_CRITICAL();
	{
		/* Create the queues used by the com test task. */
		xRxedChars = xQueueCreate( uxQueueLength, ( unsigned portBASE_TYPE ) sizeof( signed char ) );
		xCharsForTx = xQueueCreate( uxQueueLength, ( unsigned portBASE_TYPE ) sizeof( signed char ) );

		/* Calculate the baud rate register value from the equation in the
		data sheet. */
		ulBaudRateCounter = ( configCPU_CLOCK_HZ / ( serBAUD_DIV_CONSTANT * ulWantedBaud ) ) - ( unsigned long ) 1;

		/* Set the baud rate. */	
		ucByte = ( unsigned char ) ( ulBaudRateCounter & ( unsigned long ) 0xff );	
		outb( UBRRL, ucByte );

		ulBaudRateCounter >>= ( unsigned long ) 8;
		ucByte = ( unsigned char ) ( ulBaudRateCounter & ( unsigned long ) 0xff );	
		outb( UBRRH, ucByte );

		/* Enable the Rx interrupt.  The Tx interrupt will get enabled
		later. Also enable the Rx and Tx. */
		outb( UCSRB, serRX_INT_ENABLE | serRX_ENABLE | serTX_ENABLE );

		/* Set the data bits to 8. */
		outb( UCSRC, serUCSRC_SELECT | serEIGHT_DATA_BITS );
	}
	portEXIT_CRITICAL();
	
	/* Unlike other ports, this serial code does not allow for more than one
	com port.  We therefore don't return a pointer to a port structure and can
	instead just return NULL. */
	return NULL;
}
/*-----------------------------------------------------------*/

signed portBASE_TYPE xSerialGetChar( xComPortHandle pxPort, signed char *pcRxedChar, portTickType xBlockTime )
{
	/* Get the next character from the buffer.  Return false if no characters
	are available, or arrive before xBlockTime expires. */
	if( xQueueReceive( xRxedChars, pcRxedChar, xBlockTime ) )
	{
		return pdTRUE;
	}
	else
	{
		return pdFALSE;
	}
}
/*-----------------------------------------------------------*/

signed portBASE_TYPE xSerialPutChar( xComPortHandle pxPort, signed char cOutChar, portTickType xBlockTime )
{
	/* Return false if after the block time there is no room on the Tx queue. */
	if( xQueueSend( xCharsForTx, &cOutChar, xBlockTime ) != pdPASS )
	{
		return pdFAIL;
	}

	vInterruptOn();

	return pdPASS;
}
/*-----------------------------------------------------------*/

void vSerialClose( xComPortHandle xPort )
{
unsigned char ucByte;

	/* Turn off the interrupts.  We may also want to delete the queues and/or
	re-install the original ISR. */

	portENTER_CRITICAL();
	{
		vInterruptOff();
		ucByte = UCSRB;
		ucByte &= ~serRX_INT_ENABLE;
		outb( UCSRB, ucByte );
	}
	portEXIT_CRITICAL();
}
/*-----------------------------------------------------------*/

__interrupt void SIG_UART_RECV( void )
{
signed char ucChar, xHigherPriorityTaskWoken = pdFALSE;

	/* Get the character and post it on the queue of Rxed characters.
	If the post causes a task to wake force a context switch as the woken task
	may have a higher priority than the task we have interrupted. */
	ucChar = UDR;

	xQueueSendFromISR( xRxedChars, &ucChar, &xHigherPriorityTaskWoken );

	if( xHigherPriorityTaskWoken != pdFALSE )
	{
		taskYIELD();
	}
}
/*-----------------------------------------------------------*/

__interrupt void SIG_UART_DATA( void )
{
signed char cChar, cTaskWoken = pdFALSE;

	if( xQueueReceiveFromISR( xCharsForTx, &cChar, &cTaskWoken ) == pdTRUE )
	{
		/* Send the next character queued for Tx. */
		outb( UDR, cChar );
	}
	else
	{
		/* Queue empty, nothing to send. */
		vInterruptOff();
	}
}