FreeRTOS/Demo/ARM7_LPC2106_GCC/serial/serial.c

/*
	FreeRTOS V4.0.1 - Copyright (C) 2003-2006 Richard Barry.

	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 as published by
	the Free Software Foundation; either version 2 of the License, or
	(at your option) any later version.

	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

	A special exception to the GPL can be applied should you wish to distribute
	a combined work that includes FreeRTOS, without being obliged to provide
	the source code for any proprietary components.  See the licensing section 
	of http://www.FreeRTOS.org for full details of how and when the exception
	can be applied.

	***************************************************************************
	See http://www.FreeRTOS.org for documentation, latest information, license 
	and contact details.  Please ensure to read the configuration and relevant 
	port sections of the online documentation.
	***************************************************************************
*/

/*
	Changes from V2.4.0

		+ Made serial ISR handling more complete and robust.

	Changes from V2.4.1

		+ Split serial.c into serial.c and serialISR.c.  serial.c can be 
		  compiled using ARM or THUMB modes.  serialISR.c must always be
		  compiled in ARM mode.
		+ Another small change to cSerialPutChar().

	Changed from V2.5.1

		+ In cSerialPutChar() an extra check is made to ensure the post to
		  the queue was successful if then attempting to retrieve the posted
		  character.

*/

/* 
	BASIC INTERRUPT DRIVEN SERIAL PORT DRIVER FOR UART0. 

	This file contains all the serial port components that can be compiled to
	either ARM or THUMB mode.  Components that must be compiled to ARM mode are
	contained in serialISR.c.
*/

/* Standard includes. */
#include <stdlib.h>

/* Scheduler includes. */
#include "FreeRTOS.h"
#include "queue.h"
#include "task.h"

/* Demo application includes. */
#include "serial.h"

/*-----------------------------------------------------------*/

/* Constants to setup and access the UART. */
#define serDLAB							( ( unsigned portCHAR ) 0x80 )
#define serENABLE_INTERRUPTS			( ( unsigned portCHAR ) 0x03 )
#define serNO_PARITY					( ( unsigned portCHAR ) 0x00 )
#define ser1_STOP_BIT					( ( unsigned portCHAR ) 0x00 )
#define ser8_BIT_CHARS					( ( unsigned portCHAR ) 0x03 )
#define serFIFO_ON						( ( unsigned portCHAR ) 0x01 )
#define serCLEAR_FIFO					( ( unsigned portCHAR ) 0x06 )
#define serWANTED_CLOCK_SCALING			( ( unsigned portLONG ) 16 )

/* Constants to setup and access the VIC. */
#define serUART0_VIC_CHANNEL			( ( unsigned portLONG ) 0x0006 )
#define serUART0_VIC_CHANNEL_BIT		( ( unsigned portLONG ) 0x0040 )
#define serUART0_VIC_ENABLE				( ( unsigned portLONG ) 0x0020 )
#define serCLEAR_VIC_INTERRUPT			( ( unsigned portLONG ) 0 )

#define serINVALID_QUEUE				( ( xQueueHandle ) 0 )
#define serHANDLE						( ( xComPortHandle ) 1 )
#define serNO_BLOCK						( ( portTickType ) 0 )

/*-----------------------------------------------------------*/

/* Queues used to hold received characters, and characters waiting to be
transmitted. */
static xQueueHandle xRxedChars; 
static xQueueHandle xCharsForTx; 

/*-----------------------------------------------------------*/

/* Communication flag between the interrupt service routine and serial API. */
static volatile portLONG *plTHREEmpty;

/* 
 * The queues are created in serialISR.c as they are used from the ISR.
 * Obtain references to the queues and THRE Empty flag. 
 */
extern void vSerialISRCreateQueues(	unsigned portBASE_TYPE uxQueueLength, xQueueHandle *pxRxedChars, xQueueHandle *pxCharsForTx, portLONG volatile **pplTHREEmptyFlag );

/*-----------------------------------------------------------*/

xComPortHandle xSerialPortInitMinimal( unsigned portLONG ulWantedBaud, unsigned portBASE_TYPE uxQueueLength )
{
unsigned portLONG ulDivisor, ulWantedClock;
xComPortHandle xReturn = serHANDLE;
extern void ( vUART_ISR )( void );

	/* The queues are used in the serial ISR routine, so are created from
	serialISR.c (which is always compiled to ARM mode. */
	vSerialISRCreateQueues( uxQueueLength, &xRxedChars, &xCharsForTx, &plTHREEmpty );

	if( 
		( xRxedChars != serINVALID_QUEUE ) && 
		( xCharsForTx != serINVALID_QUEUE ) && 
		( ulWantedBaud != ( unsigned portLONG ) 0 ) 
	  )
	{
		portENTER_CRITICAL();
		{
			/* Setup the baud rate:  Calculate the divisor value. */
			ulWantedClock = ulWantedBaud * serWANTED_CLOCK_SCALING;
			ulDivisor = configCPU_CLOCK_HZ / ulWantedClock;

			/* Set the DLAB bit so we can access the divisor. */
			UART0_LCR |= serDLAB;

			/* Setup the divisor. */
			UART0_DLL = ( unsigned portCHAR ) ( ulDivisor & ( unsigned portLONG ) 0xff );
			ulDivisor >>= 8;
			UART0_DLM = ( unsigned portCHAR ) ( ulDivisor & ( unsigned portLONG ) 0xff );

			/* Turn on the FIFO's and clear the buffers. */
			UART0_FCR = ( serFIFO_ON | serCLEAR_FIFO );

			/* Setup transmission format. */
			UART0_LCR = serNO_PARITY | ser1_STOP_BIT | ser8_BIT_CHARS;

			/* Setup the VIC for the UART. */
			VICIntSelect &= ~( serUART0_VIC_CHANNEL_BIT );
			VICIntEnable |= serUART0_VIC_CHANNEL_BIT;
			VICVectAddr1 = ( portLONG ) vUART_ISR;
			VICVectCntl1 = serUART0_VIC_CHANNEL | serUART0_VIC_ENABLE;

			/* Enable UART0 interrupts. */
			UART0_IER |= serENABLE_INTERRUPTS;
		}
		portEXIT_CRITICAL();
	}
	else
	{
		xReturn = ( xComPortHandle ) 0;
	}

	return xReturn;
}
/*-----------------------------------------------------------*/

signed portBASE_TYPE xSerialGetChar( xComPortHandle pxPort, signed portCHAR *pcRxedChar, portTickType xBlockTime )
{
	/* The port handle is not required as this driver only supports UART0. */
	( void ) pxPort;

	/* 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;
	}
}
/*-----------------------------------------------------------*/

void vSerialPutString( xComPortHandle pxPort, const signed portCHAR * const pcString, unsigned portSHORT usStringLength )
{
signed portCHAR *pxNext;

	/* NOTE: This implementation does not handle the queue being full as no
	block time is used! */

	/* The port handle is not required as this driver only supports UART0. */
	( void ) pxPort;
	( void ) usStringLength;

	/* Send each character in the string, one at a time. */
	pxNext = ( signed portCHAR * ) pcString;
	while( *pxNext )
	{
		xSerialPutChar( pxPort, *pxNext, serNO_BLOCK );
		pxNext++;
	}
}
/*-----------------------------------------------------------*/

signed portBASE_TYPE xSerialPutChar( xComPortHandle pxPort, signed portCHAR cOutChar, portTickType xBlockTime )
{
signed portBASE_TYPE xReturn;

	/* This demo driver only supports one port so the parameter is not used. */
	( void ) pxPort;

	portENTER_CRITICAL();
	{
		/* Is there space to write directly to the UART? */
		if( *plTHREEmpty == ( portLONG ) pdTRUE )
		{
			/* We wrote the character directly to the UART, so was 
			successful. */
			*plTHREEmpty = pdFALSE;
			UART0_THR = cOutChar;
			xReturn = pdPASS;
		}
		else 
		{
			/* We cannot write directly to the UART, so queue the character.
			Block for a maximum of xBlockTime if there is no space in the
			queue. */
			xReturn = xQueueSend( xCharsForTx, &cOutChar, xBlockTime );

			/* Depending on queue sizing and task prioritisation:  While we 
			were blocked waiting to post interrupts were not disabled.  It is 
			possible that the serial ISR has emptied the Tx queue, in which
			case we need to start the Tx off again. */
			if( ( *plTHREEmpty == ( portLONG ) pdTRUE ) && ( xReturn == pdPASS ) )
			{
				xQueueReceive( xCharsForTx, &cOutChar, serNO_BLOCK );
				*plTHREEmpty = pdFALSE;
				UART0_THR = cOutChar;
			}
		}
	}
	portEXIT_CRITICAL();

	return xReturn;
}
/*-----------------------------------------------------------*/

void vSerialClose( xComPortHandle xPort )
{
	/* Not supported as not required by the demo application. */
	( void ) xPort;
}
/*-----------------------------------------------------------*/