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FreeRTOS V8.0.1 - Copyright (C) 2014 Real Time Engineers Ltd.
All rights reserved
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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 modification 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. Full license text is available from the following
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*************************************************************************** - Documentation, books, training, latest versions,
license and Real Time Engineers Ltd. contact details. - A selection of FreeRTOS ecosystem products,
including FreeRTOS+Trace - an indispensable productivity tool, a DOS
compatible FAT file system, and our tiny thread aware UDP/IP stack. - Real Time Engineers ltd license FreeRTOS to High
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* 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_PERIOD_MS )
/* The semaphore used to synchronise the button push task with the interrupt. */
static SemaphoreHandle_t 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 );