serial.c

FreeRTOS

/*
	FreeRTOS V2.6.0 - Copyright (C) 2003 - 2005 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.
	***************************************************************************
*/


/* 
	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 "projdefs.h"
#include "portable.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 serU0VIC_CHANNEL				( ( unsigned portLONG ) 0x0006 )
#define serU0VIC_CHANNEL_BIT			( ( unsigned portLONG ) 0x0040 )
#define serU0VIC_ENABLE					( ( unsigned portLONG ) 0x0020 )

/* Misc. */
#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 portCHAR ucQueueLength, xQueueHandle *pxRxedChars, xQueueHandle *pxCharsForTx, portLONG volatile **pplTHREEmptyFlag );

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

xComPortHandle xSerialPortInitMinimal( unsigned portLONG ulWantedBaud, unsigned portCHAR ucQueueLength )
{
unsigned portLONG ulDivisor, ulWantedClock;
xComPortHandle xReturn = serHANDLE;

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

	if( 
		( xRxedChars != serINVALID_QUEUE ) && 
		( xCharsForTx != serINVALID_QUEUE ) && 
		( ulWantedBaud != ( unsigned portLONG ) 0 ) 
	  )
	{
		portENTER_CRITICAL();
		{
			/* The reference to the ISR function is required to load into the 
			interrupt controller.  The prototype is slightly different 
			depending on whether in ARM or THUMB mode. */
			#ifdef KEIL_THUMB_INTERWORK
				extern void ( vUART_ISR )( void ) __arm __task;
			#else
				extern void ( vUART_ISR )( void ) __task;
			#endif

			/* Setup the baud rate:  Calculate the divisor value. */
			ulWantedClock = ulWantedBaud * serWANTED_CLOCK_SCALING;
			ulDivisor = portCPU_CLOCK_HZ / ulWantedClock;

			/* Set the DLAB bit so we can access the divisor. */
			U0LCR |= serDLAB;

			/* Setup the divisor. */
			U0DLL = ( unsigned portCHAR ) ( ulDivisor & ( unsigned portLONG ) 0xff );
			ulDivisor >>= 8;
			U0DLM = ( unsigned portCHAR ) ( ulDivisor & ( unsigned portLONG ) 0xff );

			/* Turn on the FIFO's and clear the buffers. */
			U0FCR = ( serFIFO_ON | serCLEAR_FIFO );

			/* Setup transmission format. */
			U0LCR = serNO_PARITY | ser1_STOP_BIT | ser8_BIT_CHARS;

			/* Setup the VIC for the UART. */
			VICIntSelect &= ~( serU0VIC_CHANNEL_BIT );
			VICIntEnable |= serU0VIC_CHANNEL_BIT;
			VICVectAddr1 = ( unsigned portLONG ) vUART_ISR;
			VICVectCntl1 = serU0VIC_CHANNEL | serU0VIC_ENABLE;

			/* Enable UART0 interrupts. */
			U0IER |= serENABLE_INTERRUPTS;
		}
		portEXIT_CRITICAL();
	}
	else
	{
		xReturn = ( xComPortHandle ) 0;
	}

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

signed portCHAR cSerialGetChar( 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( cQueueReceive( xRxedChars, pcRxedChar, xBlockTime ) )
	{
		return ( signed portCHAR ) pdTRUE;
	}
	else
	{
		return ( signed portCHAR ) 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;

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

signed portCHAR cSerialPutChar( xComPortHandle pxPort, signed portCHAR cOutChar, portTickType xBlockTime )
{
signed portCHAR cReturn;

	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;
			U0THR = cOutChar;
			cReturn = ( signed portCHAR ) 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.  It is ok to block within a critical section as each
			task has it's own critical section management. */
			cReturn = cQueueSend( 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 )
			{
				cQueueReceive( xCharsForTx, &cOutChar, serNO_BLOCK );
				*plTHREEmpty = pdFALSE;
				U0THR = cOutChar;
			}
		}
	}
	portEXIT_CRITICAL();

	return cReturn;
}
/*-----------------------------------------------------------*/