20100923-V6.1.0-RC2/Demo/NEC_78K0R_IAR/ButtonTask.c

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+/*
+    FreeRTOS V6.1.0 - Copyright (C) 2010 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.
+
+    http://www.SafeRTOS.com - A version that is certified for use in safety
+    critical systems.
+
+    http://www.OpenRTOS.com - Commercial support, development, porting,
+    licensing and training services.
+*/
+
+/*
+ * This file defines the button push task and ISR as described at the top of
+ * main.c.  The ISR is called from a wrapper function defined in ButtonISR.s26.
+ */
+
+/* Kernel includes. */
+#include "FreeRTOS.h"
+#include "task.h"
+#include "semphr.h"
+
+/* The LED output used by the button push task. */
+#define butLED1   P7_bit.no7
+
+/* A short delay used for button debouncing. */
+#define butDEBOUNCE_DELAY	( 200 / portTICK_RATE_MS )
+
+/* The semaphore used to synchronise the button push task with the interrupt. */
+static xSemaphoreHandle xButtonSemaphore;
+
+/*
+ * The definition of the button task itself.  See the comments at the top of
+ * main.c.
+ */
+void vButtonTask( void *pvParameters )
+{
+	/* Ensure the semaphore is created before it gets used. */
+	vSemaphoreCreateBinary( xButtonSemaphore );
+
+	for( ;; )
+	{
+		/* Block on the semaphore to wait for an interrupt event.  The semaphore
+		is 'given' from vButtonISRHandler() below.  Using portMAX_DELAY as the
+		block time will cause the task to block indefinitely provided
+		INCLUDE_vTaskSuspend is set to 1 in FreeRTOSConfig.h. */
+		xSemaphoreTake( xButtonSemaphore, portMAX_DELAY );
+
+		/* The button must have been pushed for this line to be executed.
+		Simply toggle the LED. */
+		butLED1 = !butLED1;
+		
+		/* Wait a short time then clear any pending button pushes as a crude
+		method of debouncing the switch.  xSemaphoreTake() uses a block time of
+		zero this time so it returns immediately rather than waiting for the
+		interrupt to occur. */
+		vTaskDelay( butDEBOUNCE_DELAY );
+		xSemaphoreTake( xButtonSemaphore, 0 );
+	}
+}
+/*-----------------------------------------------------------*/
+
+/*
+ * The C portion of the interrupt handler.  Interrupts are triggered by pushing
+ * the button on the target board.  This interrupt can cause a context switch
+ * so has an assembly file wrapper defined within ButtonISR.s26.
+ */
+void vButtonISRHandler( void )
+{
+short sHigherPriorityTaskWoken = pdFALSE;
+
+	/* 'Give' the semaphore to unblock the button task. */
+	xSemaphoreGiveFromISR( xButtonSemaphore, &sHigherPriorityTaskWoken );
+	
+	/* If giving the semaphore unblocked a task, and the unblocked task has a
+	priority that is higher than the currently running task, then
+	sHigherPriorityTaskWoken will have been set to pdTRUE.  Passing a pdTRUE
+	value to portYIELD_FROM_ISR() will cause this interrupt to return directly
+	to the higher priority unblocked task. */
+	portYIELD_FROM_ISR( sHigherPriorityTaskWoken );
+}
+/*-----------------------------------------------------------*/