/*
    FreeRTOS V6.1.1 - Copyright (C) 2011 Real Time Engineers Ltd.

    ***************************************************************************
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    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.

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*/


/* BASIC INTERRUPT DRIVEN SERIAL PORT DRIVER.
 *
 * This is not a proper UART driver.  It only supports one port, uses loopback
 * mode, and is used to test interrupts that use the FreeRTOS API as part of
 * a wider test suite.  Nor is it intended to show an efficient implementation
 * of a UART interrupt service routine as queues are used to pass individual
 * characters one at a time!
 */

/* Standard includes. */
#include <stdlib.h>

/* Scheduler includes. */
#include "FreeRTOS.h"
#include "queue.h"
#include "task.h"

/* Demo application includes. */
#include "serial.h"

/* Misc. constants. */
#define serNO_BLOCK				( ( portTickType ) 0 )

/* The queue used to hold received characters. */
static xQueueHandle xRxedChars;

/* The queue used to hold characters waiting transmission. */
static xQueueHandle xCharsForTx;

/*-----------------------------------------------------------*/

xComPortHandle xSerialPortInitMinimal( unsigned portLONG ulWantedBaud, unsigned portBASE_TYPE uxQueueLength )
{
unsigned portLONG ulBaudRateCount;

	/* Initialise the hardware. */

	/* Generate the baud rate constants for the wanted baud rate. */
	ulBaudRateCount = configCPU_CLOCK_HZ / ulWantedBaud;

	portENTER_CRITICAL();
	{
		/* Create the queues used by the com test task. */
		xRxedChars = xQueueCreate( uxQueueLength, ( unsigned portBASE_TYPE ) sizeof( signed portCHAR ) );
		xCharsForTx = xQueueCreate( uxQueueLength, ( unsigned portBASE_TYPE ) sizeof( signed portCHAR ) );

		/* Reset UART. */
		UCA1CTL1 |= UCSWRST;

		/* Use SMCLK. */
		UCA1CTL1 = UCSSEL0 | UCSSEL1;
		
		/* Setup baud rate low byte. */
		UCA1BR0 = ( unsigned portCHAR ) ( ulBaudRateCount & ( unsigned portLONG ) 0xff );

		/* Setup baud rate high byte. */
		ulBaudRateCount >>= 8UL;
		UCA1BR1 = ( unsigned portCHAR ) ( ulBaudRateCount & ( unsigned portLONG ) 0xff );

		/* UCLISTEN sets loopback mode! */
		UCA1STAT = UCLISTEN;

		/* Enable interrupts. */
		UCA1IE |= UCRXIE;
		
		/* Take out of reset. */
		UCA1CTL1 &= ~UCSWRST;
	}
	portEXIT_CRITICAL();
	
	/* Note the comments at the top of this file about this not being a generic
	UART driver. */
	return NULL;
}
/*-----------------------------------------------------------*/

signed portBASE_TYPE xSerialGetChar( xComPortHandle pxPort, signed portCHAR *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 portCHAR cOutChar, portTickType xBlockTime )
{
signed portBASE_TYPE xReturn;

	/* Send the next character to the queue of characters waiting transmission,
	then enable the UART Tx interrupt, just in case UART transmission has already
	completed and switched itself off. */
	xReturn = xQueueSend( xCharsForTx, &cOutChar, xBlockTime );
	UCA1IE |= UCTXIE;

	return xReturn;
}
/*-----------------------------------------------------------*/

/* The implementation of this interrupt is provided to demonstrate the use
of queues from inside an interrupt service routine.  It is *not* intended to
be an efficient interrupt implementation.  A real application should make use
of the DMA.  Or, as a minimum, transmission and reception could use a simple
RAM ring buffer, and synchronise with a task using a semaphore when a complete
message has been received or transmitted. */
#pragma vector=USCI_A1_VECTOR
static __interrupt void prvUSCI_A1_ISR( void )
{
signed char cChar;
portBASE_TYPE xHigherPriorityTaskWoken = pdFALSE;

	while( ( UCA1IFG & UCRXIFG ) != 0 )
	{
		/* Get the character from the UART and post it on the queue of Rxed
		characters. */
		cChar = UCA1RXBUF;
		xQueueSendFromISR( xRxedChars, &cChar, &xHigherPriorityTaskWoken );
	}
	
	/* If there is a Tx interrupt pending and the tx interrupts are enabled. */
	if( ( UCA1IFG & UCTXIFG ) != 0 )
	{
		/* The previous character has been transmitted.  See if there are any
		further characters waiting transmission. */
		if( xQueueReceiveFromISR( xCharsForTx, &cChar, &xHigherPriorityTaskWoken ) == pdTRUE )
		{
			/* There was another character queued - transmit it now. */
			UCA1TXBUF = cChar;
		}
		else
		{
			/* There were no other characters to transmit - disable the Tx
			interrupt. */
			UCA1IE &= ~UCTXIE;
		}
	}

	__bic_SR_register_on_exit( SCG1 + SCG0 + OSCOFF + CPUOFF );
	
	/* If writing to a queue caused a task to unblock, and the unblocked task
	has a priority equal to or above the task that this interrupt interrupted,
	then lHigherPriorityTaskWoken will have been set to pdTRUE internally within
	xQueuesendFromISR(), and portEND_SWITCHING_ISR() will ensure that this
	interrupt returns directly to the higher priority unblocked task.
	
	THIS MUST BE THE LAST THING DONE IN THE ISR. */	
	portYIELD_FROM_ISR( xHigherPriorityTaskWoken );
}