/*
    FreeRTOS V8.2.2 - Copyright (C) 2015 Real Time Engineers Ltd.
    All rights reserved

    VISIT http://www.FreeRTOS.org TO ENSURE YOU ARE USING THE LATEST VERSION.

    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 modification 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.  Full license text is available on the following
    link: http://www.freertos.org/a00114.html

    ***************************************************************************
     *                                                                       *
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    1 tab == 4 spaces!
*/

/* BASIC INTERRUPT DRIVEN SERIAL PORT DRIVER.   
 * 
 * This file only supports UART 0
 */

/* Standard includes. */
#include <stdlib.h>

/* Scheduler includes. */
#include "FreeRTOS.h"
#include "queue.h"
#include "task.h"

/* Demo application includes. */
#include "serial.h"

/* The queue used to hold received characters. */
static QueueHandle_t			xRxedChars;

/* The queue used to hold characters waiting transmission. */
static QueueHandle_t			xCharsForTx;

static volatile short	sTHREEmpty;

static volatile short	queueFail = pdFALSE;

/*-----------------------------------------------------------*/
xComPortHandle xSerialPortInitMinimal( unsigned long ulWantedBaud, unsigned portBASE_TYPE uxQueueLength )
{
	/* Initialise the hardware. */
	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) );

		if( xRxedChars == 0 )
		{
			queueFail = pdTRUE;
		}

		if( xCharsForTx == 0 )
		{
			queueFail = pdTRUE;
		}

		/* Initialize UART asynchronous mode */
		BGR0 = configCLKP1_CLOCK_HZ / ulWantedBaud;

		SCR0 = 0x17;	/* 8N1 */
		SMR0 = 0x0d;	/* enable SOT3, Reset, normal mode */
		SSR0 = 0x02;	/* LSB first, enable receive interrupts */

		PIER08_IE2 = 1; /* enable input */
		DDR08_D2 = 0;	/* switch P08_2 to input */
		DDR08_D3 = 1;	/* switch P08_3 to output */
	}
	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, TickType_t 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, TickType_t xBlockTime )
{
signed portBASE_TYPE	xReturn;

	/* Transmit a character. */
	portENTER_CRITICAL();
	{
		if( sTHREEmpty == pdTRUE )
		{
			/* If sTHREEmpty is true then the UART Tx ISR has indicated that 
			there are no characters queued to be transmitted - so we can
			write the character directly to the shift Tx register. */
			sTHREEmpty = pdFALSE;
			TDR0 = cOutChar;
			xReturn = pdPASS;
		}
		else
		{
			/* sTHREEmpty is false, so there are still characters waiting to be
			transmitted.  We have to queue this character so it gets 
			transmitted	in turn. */

			/* Return false if after the block time there is no room on the Tx 
			queue.  It is ok to block inside a critical section as each task
			maintains it's own critical section status. */
			if( xQueueSend(xCharsForTx, &cOutChar, xBlockTime) == pdTRUE )
			{
				xReturn = pdPASS;
			}
			else
			{
				xReturn = pdFAIL;
			}
		}

		if( pdPASS == xReturn )
		{
			/* Turn on the Tx interrupt so the ISR will remove the character from the
			queue and send it.   This does not need to be in a critical section as
			if the interrupt has already removed the character the next interrupt
			will simply turn off the Tx interrupt again. */
			SSR0_TIE = 1;
		}
	}
	portEXIT_CRITICAL();

	return pdPASS;
}
/*-----------------------------------------------------------*/

/*
 * UART RX interrupt service routine.
 */
__interrupt void UART0_RxISR( void )
{
volatile signed char	cChar;
portBASE_TYPE xHigherPriorityTaskWoken = pdFALSE;

	/* Get the character from the UART and post it on the queue of Rxed 
	characters. */
	cChar = RDR0;

	xQueueSendFromISR( xRxedChars, ( const void *const ) &cChar, &xHigherPriorityTaskWoken );

	if( xHigherPriorityTaskWoken )
	{
		/*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. */
		portYIELD_FROM_ISR();
	}
}
/*-----------------------------------------------------------*/

/*
 * UART Tx interrupt service routine.
 */
__interrupt void UART0_TxISR( void )
{
signed char			cChar;
signed portBASE_TYPE	xTaskWoken = pdFALSE;

	/* The previous character has been transmitted.  See if there are any
	further characters waiting transmission. */
	if( xQueueReceiveFromISR(xCharsForTx, &cChar, &xTaskWoken) == pdTRUE )
	{
		/* There was another character queued - transmit it now. */
		TDR0 = cChar;
	}
	else
	{
		/* There were no other characters to transmit. */
		sTHREEmpty = pdTRUE;

		/* Disable transmit interrupts */
		SSR0_TIE = 0;
	}
}