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    ***************************************************************************
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    This file is part of the FreeRTOS distribution.

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*/

/*
Changes from V1.00:
	
	+ Call to the more efficient portSWITCH_CONTEXT() replaces the call to 
	  taskYIELD() in the ISR.

Changes from V1.01:

	+ The semaphore task is not operational.  This does nothing but check
	  the semaphore from ISR functionality.
	+ ISR modified slightly so only Rx or Tx is serviced per ISR - not both.

Changes from V1.2.0:

	+ Change so Tx uses a DMA channel, and Rx uses an interrupt.

Changes from V1.2.3

	+ The function xPortInitMinimal() has been renamed to 
	  xSerialPortInitMinimal() and the function xPortInit() has been renamed
	  to xSerialPortInit().

Changes from V1.2.5

	+ Reverted back to the non-DMA serial port driver, with a slightly modified
	  ISR.  This is a better test of the scheduler mechanisms.
	+ A critical section is now used in vInterruptOn().
	+ Flag sTxInterruptOn has been added to the port structure.  This allows
	  checking of the interrupt enable status without performing any IO.

Changes from V2.0.0

	+ Use portTickType in place of unsigned pdLONG for delay periods.
	+ Slightly more efficient vSerialSendString() implementation.
	+ cQueueReieveFromISR() used in place of xQueueReceive() in ISR.
*/

#include <stdlib.h>
#include <dos.h>
#include "FreeRTOS.h"
#include "queue.h"
#include "task.h"
#include "portasm.h"
#include "semphr.h"

#define serMAX_PORTS			( ( unsigned short ) 2 )

#define serPORT_0_INT_REG		( 0xff44 )
#define serPORT_0_BAUD_REG		( 0xff88 )
#define serPORT_0_RX_REG		( 0xff86 )
#define serPORT_0_TX_REG		( 0xff84 )
#define serPORT_0_STATUS_REG	( 0xff82 )
#define serPORT_0_CTRL_REG		( 0xff80 )
#define serPORT_0_IRQ			( 0x14 )

#define serPORT_1_INT_REG		( 0xff42 )
#define serPORT_1_BAUD_REG		( 0xff18 )
#define serPORT_1_RX_REG		( 0xff16 )
#define serPORT_1_TX_REG		( 0xff14 )
#define serPORT_1_STATUS_REG	( 0xff12 )
#define serPORT_1_CTRL_REG		( 0xff10 )
#define serPORT_1_IRQ			( 0x11 )

#define serTX_EMPTY				( ( unsigned short ) 0x40 )
#define serRX_READY				( ( unsigned short ) 0x80 )

#define serRESET_PIC( usEOI_TYPE )	portOUTPUT_WORD( ( unsigned short ) 0xff22, usEOI_TYPE )
#define serTX_HOLD_EMPTY_INT		( ( unsigned short ) 0x100 )

#define serENABLE_INTERRUPTS		( ( unsigned short ) 0x80 )
#define serMODE						( ( unsigned short ) 0x01 )
#define serENABLE_TX_MACHINES		( ( unsigned short ) 0x40 )
#define serENABLE_RX_MACHINES		( ( unsigned short ) 0x20 )
#define serINTERRUPT_MASK			( ( unsigned short ) 0x08 )
#define serCLEAR_ALL_STATUS_BITS	( ( unsigned short ) 0x00 )
#define serINTERRUPT_PRIORITY		( ( unsigned short ) 0x01 ) /*< Just below the scheduler priority. */

#define serDONT_BLOCK				( ( portTickType ) 0 )

typedef enum
{ 
	serCOM1 = 0, 
	serCOM2, 
	serCOM3, 
	serCOM4, 
	serCOM5, 
	serCOM6, 
	serCOM7, 
	serCOM8 
} eCOMPort;

typedef enum 
{ 
	serNO_PARITY, 
	serODD_PARITY, 
	serEVEN_PARITY, 
	serMARK_PARITY, 
	serSPACE_PARITY 
} eParity;

typedef enum 
{ 
	serSTOP_1, 
	serSTOP_2 
} eStopBits;

typedef enum 
{ 
	serBITS_5, 
	serBITS_6, 
	serBITS_7, 
	serBITS_8 
} eDataBits;

typedef enum 
{ 
	ser50 = 0,
	ser75,		
	ser110,		
	ser134,		
	ser150,    
	ser200,
	ser300,		
	ser600,		
	ser1200,	
	ser1800,	
	ser2400,   
	ser4800,
	ser9600,		
	ser19200,	
	ser38400,	
	ser57600,	
	ser115200
} eBaud;

/* Must be same order as eBaud definitions. */
static const unsigned short usBaudRateDivisor[] = 
{
	0, /* Not sure if the first 6 are correct.  First cannot be used. */
	29127,
	19859,
	16302,
	14564,
	10923,	
	6879,
	3437,
	1718,
	1145,
	859,
	429,
	214,
	107,
	54,
	35,
	18
};


typedef struct xCOM_PORT
{
	/* Hardware parameters for this port. */
	short sTxInterruptOn;
	unsigned short usIntReg;
	unsigned short usBaudReg;
	unsigned short usRxReg;
	unsigned short usTxReg;
	unsigned short usStatusReg;
	unsigned short usCtrlReg;

	unsigned short usIRQVector;

	/* Queues used for communications with com test task. */
	xQueueHandle xRxedChars; 
	xQueueHandle xCharsForTx;

	/* This semaphore does nothing useful except test a feature of the
	scheduler. */
	xSemaphoreHandle xTestSem;

} xComPort;

static xComPort xPorts[ serMAX_PORTS ] = 
{
	{ pdFALSE, serPORT_0_INT_REG, serPORT_0_BAUD_REG, serPORT_0_RX_REG, serPORT_0_TX_REG, serPORT_0_STATUS_REG, serPORT_0_CTRL_REG, serPORT_0_IRQ, NULL, NULL, NULL },
	{ pdFALSE, serPORT_1_INT_REG, serPORT_1_BAUD_REG, serPORT_1_RX_REG, serPORT_1_TX_REG, serPORT_1_STATUS_REG, serPORT_1_CTRL_REG, serPORT_1_IRQ, NULL, NULL, NULL }
};

typedef xComPort * xComPortHandle;

/* These prototypes are repeated here so we don't have to include the serial header.  This allows
the xComPortHandle structure details to be private to this file. */
xComPortHandle xSerialPortInit( eCOMPort ePort, eBaud eWantedBaud, eParity eWantedParity, eDataBits eWantedDataBits, eStopBits eWantedStopBits, unsigned portBASE_TYPE uxBufferLength );
portBASE_TYPE xSerialGetChar( xComPortHandle pxPort, char *pcRxedChar, portTickType xBlockTime );
portBASE_TYPE xSerialPutChar( xComPortHandle pxPort, char cOutChar, portTickType xBlockTime );
void vSerialClose( xComPortHandle xPort );
short sSerialWaitForSemaphore( xComPortHandle xPort );
/*-----------------------------------------------------------*/

static short xComPortISR( xComPort * const pxPort );

#define vInterruptOn( pxPort, usInterrupt )										\
{																				\
unsigned short usIn;														\
																				\
	portENTER_CRITICAL();														\
	{																			\
		if( pxPort->sTxInterruptOn == pdFALSE )									\
		{																		\
			usIn = portINPUT_WORD( pxPort->usCtrlReg );							\
			portOUTPUT_WORD( pxPort->usCtrlReg, usIn | usInterrupt );			\
																				\
			pxPort->sTxInterruptOn = pdTRUE;									\
		}																		\
	}																			\
	portEXIT_CRITICAL();															\
}																				
/*-----------------------------------------------------------*/

#define vInterruptOff( pxPort, usInterrupt )									\
{																				\
	unsigned short usIn = portINPUT_WORD( pxPort->usCtrlReg );				\
	if( usIn & usInterrupt )													\
	{																			\
		portOUTPUT_WORD( pxPort->usCtrlReg, usIn & ~usInterrupt);				\
		pxPort->sTxInterruptOn = pdFALSE;										\
	}																			\
}
/*-----------------------------------------------------------*/


/* Define an interrupt handler for each port */
#define COM_IRQ_WRAPPER(N)										\
	static void __interrupt COM_IRQ##N##_WRAPPER( void )		\
	{															\
        if( xComPortISR( &( xPorts[##N##] ) ) )                 \
        {                                                       \
			portSWITCH_CONTEXT();                             \
		}                                                       \
	}

  

COM_IRQ_WRAPPER( 0 )
COM_IRQ_WRAPPER( 1 )

static pxISR xISRs[ serMAX_PORTS ] = 
{
	COM_IRQ0_WRAPPER, 
	COM_IRQ1_WRAPPER
};

/*-----------------------------------------------------------*/

xComPortHandle xSerialPortInit( eCOMPort ePort, eBaud eWantedBaud, eParity eWantedParity, eDataBits eWantedDataBits, eStopBits eWantedStopBits, unsigned portBASE_TYPE uxBufferLength )
{
unsigned short usPort;
xComPortHandle pxPort = NULL;

/* BAUDDIV = ( Microprocessor Clock / Baud Rate ) / 16 */

	/* Only n, 8, 1 is supported so these parameters are not required for this
	port. */
	( void ) eWantedParity;
	( void ) eWantedDataBits;
    ( void ) eWantedStopBits;

	/* Currently only n,8,1 is supported. */

	usPort = ( unsigned short ) ePort;
	
	if( usPort < serMAX_PORTS )
	{
		pxPort = &( xPorts[ usPort ] );

		portENTER_CRITICAL();
		{
			unsigned short usInWord;

			/* Create the queues used by the com test task. */
			pxPort->xRxedChars = xQueueCreate( uxBufferLength, ( unsigned portBASE_TYPE ) sizeof( char ) );
			pxPort->xCharsForTx = xQueueCreate( uxBufferLength, ( unsigned portBASE_TYPE ) sizeof( char ) );

			/* Create the test semaphore.  This does nothing useful except test a feature of the scheduler. */
			vSemaphoreCreateBinary( pxPort->xTestSem );

			/* There is no ISR here already to restore later. */
			_dos_setvect( ( short ) pxPort->usIRQVector, xISRs[ usPort ] );

			usInWord = portINPUT_WORD( pxPort->usIntReg );
			usInWord &= ~serINTERRUPT_MASK;
			usInWord |= serINTERRUPT_PRIORITY;
			portOUTPUT_WORD( pxPort->usIntReg, usInWord );

			portOUTPUT_WORD( pxPort->usBaudReg, usBaudRateDivisor[ eWantedBaud ] );
			portOUTPUT_WORD( pxPort->usCtrlReg, serENABLE_INTERRUPTS | serMODE | serENABLE_TX_MACHINES | serENABLE_RX_MACHINES );

			portOUTPUT_WORD( pxPort->usStatusReg, serCLEAR_ALL_STATUS_BITS );
		}
		portEXIT_CRITICAL();
	}

	return pxPort;
} /*lint !e715 Some parameters are not used as only a subset of the serial port functionality is currently implemented. */
/*-----------------------------------------------------------*/

void vSerialPutString( xComPortHandle pxPort, const char * const pcString, unsigned short usStringLength )
{
unsigned short usByte;
char *pcNextChar;

	pcNextChar = ( char * ) pcString;

	for( usByte = 0; usByte < usStringLength; usByte++ )
	{
		xQueueSend( pxPort->xCharsForTx, pcNextChar, serDONT_BLOCK );
		pcNextChar++;
	}

	vInterruptOn( pxPort, serTX_HOLD_EMPTY_INT );
}
/*-----------------------------------------------------------*/

portBASE_TYPE xSerialGetChar( xComPortHandle pxPort, char *pcRxedChar, portTickType xBlockTime )
{
	/* Get the next character from the buffer, note that this routine is only 
	called having checked that the is (at least) one to get */
	if( xQueueReceive( pxPort->xRxedChars, pcRxedChar, xBlockTime ) )
	{
		return pdTRUE;
	}
	else
	{
		return pdFALSE;
	}
}
/*-----------------------------------------------------------*/

portBASE_TYPE xSerialPutChar( xComPortHandle pxPort, char cOutChar, portTickType xBlockTime )
{
	if( xQueueSend( pxPort->xCharsForTx, &cOutChar, xBlockTime ) != pdPASS )
	{
		return pdFAIL;
	}

	vInterruptOn( pxPort, serTX_HOLD_EMPTY_INT );

	return pdPASS;
}
/*-----------------------------------------------------------*/

portBASE_TYPE xSerialWaitForSemaphore( xComPortHandle xPort )
{
const portTickType xBlockTime = ( portTickType ) 0xffff;

	/* This function does nothing interesting, but test the 
	semaphore from ISR mechanism. */
	return xSemaphoreTake( xPort->xTestSem, xBlockTime );
}
/*-----------------------------------------------------------*/

void vSerialClose( xComPortHandle xPort )
{
unsigned short usOutput;

	/* Turn off the interrupts.  We may also want to delete the queues and/or
	re-install the original ISR. */

	portENTER_CRITICAL();
	{
		usOutput = portINPUT_WORD( xPort->usCtrlReg );

		usOutput &= ~serENABLE_INTERRUPTS;
		usOutput &= ~serENABLE_TX_MACHINES;
		usOutput &= ~serENABLE_RX_MACHINES;
		portOUTPUT_WORD( xPort->usCtrlReg, usOutput );

		usOutput = portINPUT_WORD( xPort->usIntReg );
		usOutput |= serINTERRUPT_MASK;
		portOUTPUT_WORD( xPort->usIntReg, usOutput );
	}
	portEXIT_CRITICAL();
}
/*-----------------------------------------------------------*/

static portBASE_TYPE xComPortISR( xComPort * const pxPort )
{
unsigned short usStatusRegister;
char cChar;
portBASE_TYPE xHigherPriorityTaskWoken = pdFALSE, xContinue = pdTRUE;

	/* NOTE:  THIS IS NOT AN EFFICIENT ISR AS IT IS DESIGNED SOLELY TO TEST
	THE SCHEDULER FUNCTIONALITY.  REAL APPLICATIONS SHOULD NOT USE THIS
	FUNCTION. */


	while( xContinue == pdTRUE )
	{
		xContinue = pdFALSE;
		usStatusRegister = portINPUT_WORD( pxPort->usStatusReg );

		if( usStatusRegister & serRX_READY )
		{
			cChar = ( char ) portINPUT_WORD( pxPort->usRxReg );
			xQueueSendFromISR( pxPort->xRxedChars, &cChar, &xHigherPriorityTaskWoken );

			/* Also release the semaphore - this does nothing interesting and is just a test. */
			xSemaphoreGiveFromISR( pxPort->xTestSem, &xHigherPriorityTaskWoken );

			/* We have performed an action this cycle - there may be other to perform. */
			xContinue = pdTRUE;
		}

		if( pxPort->sTxInterruptOn && ( usStatusRegister & serTX_EMPTY ) )
		{
			if( xQueueReceiveFromISR( pxPort->xCharsForTx, &cChar, &xHigherPriorityTaskWoken ) == pdTRUE )
			{
				portOUTPUT_WORD( pxPort->usTxReg, ( unsigned short ) cChar );

				/* We have performed an action this cycle - there may be others to perform. */
				xContinue = pdTRUE;
			}
			else
			{
				/* Queue empty, nothing to send */
				vInterruptOff( pxPort, serTX_HOLD_EMPTY_INT );
			}
		}
	}

	serRESET_PIC( pxPort->usIRQVector );

	/* If posting to the queue woke a task that was blocked on the queue we may
	want to switch to the woken task - depending on its priority relative to
	the task interrupted by this ISR. */
	return xHigherPriorityTaskWoken;
}