lcd.c

这个Demo程序是应用在FreeRTOS上的PIC24应用Demo

/*
	FreeRTOS.org V5.0.2 - Copyright (C) 2003-2008 Richard Barry.

	This file is part of the FreeRTOS.org distribution.

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	it under the terms of the GNU General Public License as published by
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	(at your option) any later version.

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	GNU General Public License for more details.

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	along with FreeRTOS.org; if not, write to the Free Software
	Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA

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	a combined work that includes FreeRTOS.org, 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.

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	Please ensure to read the configuration and relevant port sections of the
	online documentation.

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*/

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

/* Demo includes. */
#include "lcd.h"

/*
 * The LCD is written to by more than one task so is controlled by this
 * 'gatekeeper' task.  This is the only task that is actually permitted to
 * access the LCD directly.  Other tasks wanting to display a message send
 * the message to the gatekeeper.
 */
static void vLCDTask( void *pvParameters );

/*
 * Setup the peripherals required to communicate with the LCD.
 */
static void prvSetupLCD( void );

/* 
 * Move to the first (0) or second (1) row of the LCD. 
 */
static void prvLCDGotoRow( unsigned portSHORT usRow );

/* 
 * Write a string of text to the LCD. 
 */
static void prvLCDPutString( portCHAR *pcString );

/* 
 * Clear the LCD. 
 */
static void prvLCDClear( void );

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

/* Brief delay to permit the LCD to catch up with commands. */
#define lcdSHORT_DELAY		3

/* SFR that seems to be missing from the standard header files. */
#define PMAEN				*( ( unsigned short * ) 0x60c )

/* LCD commands. */
#define lcdDEFAULT_FUNCTION	0x3c
#define lcdDISPLAY_CONTROL	0x0c
#define lcdCLEAR_DISPLAY	0x01
#define lcdENTRY_MODE		0x06

/* The length of the queue used to send messages to the LCD gatekeeper task. */
#define lcdQUEUE_SIZE		3
/*-----------------------------------------------------------*/

/* The queue used to send messages to the LCD task. */
xQueueHandle xLCDQueue;


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

xQueueHandle xStartLCDTask( void )
{
	/* Create the queue used by the LCD task.  Messages for display on the LCD
	are received via this queue. */
	xLCDQueue = xQueueCreate( lcdQUEUE_SIZE, sizeof( xLCDMessage ) );

	/* Start the task that will write to the LCD.  The LCD hardware is
	initialised from within the task itself so delays can be used. */
	xTaskCreate( vLCDTask, ( signed portCHAR * ) "LCD", configMINIMAL_STACK_SIZE, NULL, tskIDLE_PRIORITY + 1, NULL );

	return xLCDQueue;
}
/*-----------------------------------------------------------*/

static void prvLCDGotoRow( unsigned portSHORT usRow )
{
	if( usRow == 0 )
	{
		PMADDR = 0x0000;
		PMDIN1 = 0x02;
	}
	else
	{
		PMADDR = 0x0000;
		PMDIN1 = 0xc0;
	}

	vTaskDelay( lcdSHORT_DELAY );
}
/*-----------------------------------------------------------*/

static void prvLCDPutString( portCHAR *pcString )
{
	/* Write out each character with appropriate delay between each. */
	while( *pcString )
	{
		PMADDR = 0x0001;
		PMDIN1 = *pcString;
		pcString++;
		vTaskDelay( lcdSHORT_DELAY );
	}
}
/*-----------------------------------------------------------*/

static void prvLCDClear( void )
{
	/* Clear the display. */
	PMADDR = 0x0000;
	PMDIN1 = lcdCLEAR_DISPLAY;
	vTaskDelay( lcdSHORT_DELAY );	
}
/*-----------------------------------------------------------*/

static void prvSetupLCD( void )
{
	/* Setup the PMP. */
	PMCON = 0x83BF;
	PMMODE = 0x3FF;
	PMAEN = 1;
	PMADDR = 0x0000;
	vTaskDelay( lcdSHORT_DELAY );

	/* Set the default function. */
	PMDIN1 = lcdDEFAULT_FUNCTION;
	vTaskDelay( lcdSHORT_DELAY );

	/* Set the display control. */
	PMDIN1 = lcdDISPLAY_CONTROL;
	vTaskDelay( lcdSHORT_DELAY );

	/* Clear the display. */
	PMDIN1 = lcdCLEAR_DISPLAY;
	vTaskDelay( lcdSHORT_DELAY );

	/* Set the entry mode. */
	PMDIN1 = lcdENTRY_MODE;
	vTaskDelay( lcdSHORT_DELAY );
}
/*-----------------------------------------------------------*/

static void vLCDTask( void *pvParameters )
{
xLCDMessage xMessage;
unsigned portSHORT usRow = 0;

	/* Initialise the hardware.  This uses delays so must not be called prior
	to the scheduler being started. */
	prvSetupLCD();

	/* Welcome message. */
	prvLCDPutString( "www.FreeRTOS.org" );

	for( ;; )
	{
		/* Wait for a message to arrive that requires displaying. */
		while( xQueueReceive( xLCDQueue, &xMessage, portMAX_DELAY ) != pdPASS );

		/* Clear the current display value. */
		prvLCDClear();

		/* Switch rows each time so we can see that the display is still being
		updated. */
		prvLCDGotoRow( usRow & 0x01 );
		usRow++;
		prvLCDPutString( xMessage.pcMessage );

		/* Delay the requested amount of time to ensure the text just written 
		to the LCD is not overwritten. */
		vTaskDelay( xMessage.xMinDisplayTime );		
	}
}