/*
	FreeRTOS V5.4.2 - Copyright (C) 2009 Real Time Engineers Ltd.

	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.  
	Alternative commercial license and support terms are also available upon 
	request.  See the licensing section of http://www.FreeRTOS.org for full 
	license details.

	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 along
	with FreeRTOS; if not, write to the Free Software Foundation, Inc., 59
	Temple Place, Suite 330, Boston, MA  02111-1307  USA.


	***************************************************************************
	*                                                                         *
	* Looking for a quick start?  Then check out the FreeRTOS eBook!          *
	* See http://www.FreeRTOS.org/Documentation for details                   *
	*                                                                         *
	***************************************************************************

	1 tab == 4 spaces!

	Please ensure to read the configuration and relevant port sections of the
	online documentation.

	http://www.FreeRTOS.org - Documentation, latest information, license and
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	http://www.SafeRTOS.com - A version that is certified for use in safety
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*/


/* 
	BASIC INTERRUPT DRIVEN SERIAL PORT DRIVER FOR UART0. 

	This file contains all the serial port components that must be compiled
	to ARM mode.  The components that can be compiled to either ARM or THUMB
	mode are contained in serial.c.

*/

/* Standard includes. */
#include <stdlib.h>

/* Scheduler includes. */
#include "FreeRTOS.h"
#include "queue.h"
#include "task.h"

/* Demo application includes. */
#include "serial.h"

/*-----------------------------------------------------------*/

/* Constant to access the VIC. */
#define serCLEAR_VIC_INTERRUPT			( ( unsigned portLONG ) 0 )

/* Constants to determine the ISR source. */
#define serSOURCE_THRE					( ( unsigned portCHAR ) 0x02 )
#define serSOURCE_RX_TIMEOUT			( ( unsigned portCHAR ) 0x0c )
#define serSOURCE_ERROR					( ( unsigned portCHAR ) 0x06 )
#define serSOURCE_RX					( ( unsigned portCHAR ) 0x04 )
#define serINTERRUPT_SOURCE_MASK		( ( unsigned portCHAR ) 0x0f )

/* Queues used to hold received characters, and characters waiting to be
transmitted. */
static xQueueHandle xRxedChars; 
static xQueueHandle xCharsForTx; 
static volatile portLONG lTHREEmpty;

/*-----------------------------------------------------------*/

/* 
 * The queues are created in serialISR.c as they are used from the ISR.
 * Obtain references to the queues and THRE Empty flag. 
 */
void vSerialISRCreateQueues( unsigned portBASE_TYPE uxQueueLength, xQueueHandle *pxRxedChars, xQueueHandle *pxCharsForTx, portLONG volatile **pplTHREEmptyFlag );

/* UART0 interrupt service routine entry point. */
void vUART_ISR_Wrapper( void ) __attribute__ ((naked));

/* UART0 interrupt service routine handler. */
void vUART_ISR_Handler( void ) __attribute__ ((noinline));

/*-----------------------------------------------------------*/
void vSerialISRCreateQueues(	unsigned portBASE_TYPE uxQueueLength, xQueueHandle *pxRxedChars, 
								xQueueHandle *pxCharsForTx, portLONG volatile **pplTHREEmptyFlag )
{
	/* Create the queues used to hold Rx and Tx characters. */
	xRxedChars = xQueueCreate( uxQueueLength, ( unsigned portBASE_TYPE ) sizeof( signed portCHAR ) );
	xCharsForTx = xQueueCreate( uxQueueLength + 1, ( unsigned portBASE_TYPE ) sizeof( signed portCHAR ) );

	/* Pass back a reference to the queues so the serial API file can 
	post/receive characters. */
	*pxRxedChars = xRxedChars;
	*pxCharsForTx = xCharsForTx;

	/* Initialise the THRE empty flag - and pass back a reference. */
	lTHREEmpty = ( portLONG ) pdTRUE;
	*pplTHREEmptyFlag = &lTHREEmpty;
}
/*-----------------------------------------------------------*/

void vUART_ISR_Wrapper( void )
{
	/* Save the context of the interrupted task. */
	portSAVE_CONTEXT();

	/* Call the handler.  This must be a separate function from the wrapper
	to ensure the correct stack frame is set up. */
	__asm volatile ("bl vUART_ISR_Handler");

	/* Restore the context of whichever task is going to run next. */
	portRESTORE_CONTEXT();
}
/*-----------------------------------------------------------*/

void vUART_ISR_Handler( void )
{
signed portCHAR cChar;
portBASE_TYPE xHigherPriorityTaskWoken = pdFALSE;

	/* What caused the interrupt? */
	switch( UART0_IIR & serINTERRUPT_SOURCE_MASK )
	{
		case serSOURCE_ERROR :	/* Not handling this, but clear the interrupt. */
								cChar = UART0_LSR;
								break;

		case serSOURCE_THRE	:	/* The THRE is empty.  If there is another
								character in the Tx queue, send it now. */
								if( xQueueReceiveFromISR( xCharsForTx, &cChar, &xHigherPriorityTaskWoken ) == pdTRUE )
								{
									UART0_THR = cChar;
								}
								else
								{
									/* There are no further characters 
									queued to send so we can indicate 
									that the THRE is available. */
									lTHREEmpty = pdTRUE;
								}
								break;

		case serSOURCE_RX_TIMEOUT :
		case serSOURCE_RX	:	/* A character was received.  Place it in 
								the queue of received characters. */
								cChar = UART0_RBR;
								xQueueSendFromISR( xRxedChars, &cChar, &xHigherPriorityTaskWoken );
								break;

		default				:	/* There is nothing to do, leave the ISR. */
								break;
	}

	if( xHigherPriorityTaskWoken )
	{
		portYIELD_FROM_ISR();
	}

	/* Clear the ISR in the VIC. */
	VICVectAddr = serCLEAR_VIC_INTERRUPT;
}