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diff --git a/libraries/FreeRTOS/utility/semphr.h b/libraries/FreeRTOS/utility/semphr.h new file mode 100755 index 0000000..7a9e83f --- /dev/null +++ b/libraries/FreeRTOS/utility/semphr.h @@ -0,0 +1,717 @@ +/* + FreeRTOS V7.0.1 - Copyright (C) 2011 Real Time Engineers Ltd. + + + FreeRTOS supports many tools and architectures. V7.0.0 is sponsored by: + Atollic AB - Atollic provides professional embedded systems development + tools for C/C++ development, code analysis and test automation. + See http://www.atollic.com + + + *************************************************************************** + * * + * FreeRTOS tutorial books are available in pdf and paperback. * + * Complete, revised, and edited pdf reference manuals are also * + * available. * + * * + * Purchasing FreeRTOS documentation will not only help you, by * + * ensuring you get running as quickly as possible and with an * + * in-depth knowledge of how to use FreeRTOS, it will also help * + * the FreeRTOS project to continue with its mission of providing * + * professional grade, cross platform, de facto standard solutions * + * for microcontrollers - completely free of charge! * + * * + * >>> See http://www.FreeRTOS.org/Documentation for details. <<< * + * * + * Thank you for using FreeRTOS, and thank you for your support! * + * * + *************************************************************************** + + + 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. 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. +*/ + +#ifndef SEMAPHORE_H +#define SEMAPHORE_H + +#ifndef INC_FREERTOS_H + #error "#include FreeRTOS.h" must appear in source files before "#include semphr.h" +#endif + +#include "queue.h" + +typedef xQueueHandle xSemaphoreHandle; + +#define semBINARY_SEMAPHORE_QUEUE_LENGTH ( ( unsigned char ) 1U ) +#define semSEMAPHORE_QUEUE_ITEM_LENGTH ( ( unsigned char ) 0U ) +#define semGIVE_BLOCK_TIME ( ( portTickType ) 0U ) + + +/** + * semphr. h + * <pre>vSemaphoreCreateBinary( xSemaphoreHandle xSemaphore )</pre> + * + * <i>Macro</i> that implements a semaphore by using the existing queue mechanism. + * The queue length is 1 as this is a binary semaphore. The data size is 0 + * as we don't want to actually store any data - we just want to know if the + * queue is empty or full. + * + * This type of semaphore can be used for pure synchronisation between tasks or + * between an interrupt and a task. The semaphore need not be given back once + * obtained, so one task/interrupt can continuously 'give' the semaphore while + * another continuously 'takes' the semaphore. For this reason this type of + * semaphore does not use a priority inheritance mechanism. For an alternative + * that does use priority inheritance see xSemaphoreCreateMutex(). + * + * @param xSemaphore Handle to the created semaphore. Should be of type xSemaphoreHandle. + * + * Example usage: + <pre> + xSemaphoreHandle xSemaphore; + + void vATask( void * pvParameters ) + { + // Semaphore cannot be used before a call to vSemaphoreCreateBinary (). + // This is a macro so pass the variable in directly. + vSemaphoreCreateBinary( xSemaphore ); + + if( xSemaphore != NULL ) + { + // The semaphore was created successfully. + // The semaphore can now be used. + } + } + </pre> + * \defgroup vSemaphoreCreateBinary vSemaphoreCreateBinary + * \ingroup Semaphores + */ +#define vSemaphoreCreateBinary( xSemaphore ) { \ + ( xSemaphore ) = xQueueCreate( ( unsigned portBASE_TYPE ) 1, semSEMAPHORE_QUEUE_ITEM_LENGTH ); \ + if( ( xSemaphore ) != NULL ) \ + { \ + xSemaphoreGive( ( xSemaphore ) ); \ + } \ + } + +/** + * semphr. h + * <pre>xSemaphoreTake( + * xSemaphoreHandle xSemaphore, + * portTickType xBlockTime + * )</pre> + * + * <i>Macro</i> to obtain a semaphore. The semaphore must have previously been + * created with a call to vSemaphoreCreateBinary(), xSemaphoreCreateMutex() or + * xSemaphoreCreateCounting(). + * + * @param xSemaphore A handle to the semaphore being taken - obtained when + * the semaphore was created. + * + * @param xBlockTime The time in ticks to wait for the semaphore to become + * available. The macro portTICK_RATE_MS can be used to convert this to a + * real time. A block time of zero can be used to poll the semaphore. A block + * time of portMAX_DELAY can be used to block indefinitely (provided + * INCLUDE_vTaskSuspend is set to 1 in FreeRTOSConfig.h). + * + * @return pdTRUE if the semaphore was obtained. pdFALSE + * if xBlockTime expired without the semaphore becoming available. + * + * Example usage: + <pre> + xSemaphoreHandle xSemaphore = NULL; + + // A task that creates a semaphore. + void vATask( void * pvParameters ) + { + // Create the semaphore to guard a shared resource. + vSemaphoreCreateBinary( xSemaphore ); + } + + // A task that uses the semaphore. + void vAnotherTask( void * pvParameters ) + { + // ... Do other things. + + if( xSemaphore != NULL ) + { + // See if we can obtain the semaphore. If the semaphore is not available + // wait 10 ticks to see if it becomes free. + if( xSemaphoreTake( xSemaphore, ( portTickType ) 10 ) == pdTRUE ) + { + // We were able to obtain the semaphore and can now access the + // shared resource. + + // ... + + // We have finished accessing the shared resource. Release the + // semaphore. + xSemaphoreGive( xSemaphore ); + } + else + { + // We could not obtain the semaphore and can therefore not access + // the shared resource safely. + } + } + } + </pre> + * \defgroup xSemaphoreTake xSemaphoreTake + * \ingroup Semaphores + */ +#define xSemaphoreTake( xSemaphore, xBlockTime ) xQueueGenericReceive( ( xQueueHandle ) ( xSemaphore ), NULL, ( xBlockTime ), pdFALSE ) + +/** + * semphr. h + * xSemaphoreTakeRecursive( + * xSemaphoreHandle xMutex, + * portTickType xBlockTime + * ) + * + * <i>Macro</i> to recursively obtain, or 'take', a mutex type semaphore. + * The mutex must have previously been created using a call to + * xSemaphoreCreateRecursiveMutex(); + * + * configUSE_RECURSIVE_MUTEXES must be set to 1 in FreeRTOSConfig.h for this + * macro to be available. + * + * This macro must not be used on mutexes created using xSemaphoreCreateMutex(). + * + * A mutex used recursively can be 'taken' repeatedly by the owner. The mutex + * doesn't become available again until the owner has called + * xSemaphoreGiveRecursive() for each successful 'take' request. For example, + * if a task successfully 'takes' the same mutex 5 times then the mutex will + * not be available to any other task until it has also 'given' the mutex back + * exactly five times. + * + * @param xMutex A handle to the mutex being obtained. This is the + * handle returned by xSemaphoreCreateRecursiveMutex(); + * + * @param xBlockTime The time in ticks to wait for the semaphore to become + * available. The macro portTICK_RATE_MS can be used to convert this to a + * real time. A block time of zero can be used to poll the semaphore. If + * the task already owns the semaphore then xSemaphoreTakeRecursive() will + * return immediately no matter what the value of xBlockTime. + * + * @return pdTRUE if the semaphore was obtained. pdFALSE if xBlockTime + * expired without the semaphore becoming available. + * + * Example usage: + <pre> + xSemaphoreHandle xMutex = NULL; + + // A task that creates a mutex. + void vATask( void * pvParameters ) + { + // Create the mutex to guard a shared resource. + xMutex = xSemaphoreCreateRecursiveMutex(); + } + + // A task that uses the mutex. + void vAnotherTask( void * pvParameters ) + { + // ... Do other things. + + if( xMutex != NULL ) + { + // See if we can obtain the mutex. If the mutex is not available + // wait 10 ticks to see if it becomes free. + if( xSemaphoreTakeRecursive( xSemaphore, ( portTickType ) 10 ) == pdTRUE ) + { + // We were able to obtain the mutex and can now access the + // shared resource. + + // ... + // For some reason due to the nature of the code further calls to + // xSemaphoreTakeRecursive() are made on the same mutex. In real + // code these would not be just sequential calls as this would make + // no sense. Instead the calls are likely to be buried inside + // a more complex call structure. + xSemaphoreTakeRecursive( xMutex, ( portTickType ) 10 ); + xSemaphoreTakeRecursive( xMutex, ( portTickType ) 10 ); + + // The mutex has now been 'taken' three times, so will not be + // available to another task until it has also been given back + // three times. Again it is unlikely that real code would have + // these calls sequentially, but instead buried in a more complex + // call structure. This is just for illustrative purposes. + xSemaphoreGiveRecursive( xMutex ); + xSemaphoreGiveRecursive( xMutex ); + xSemaphoreGiveRecursive( xMutex ); + + // Now the mutex can be taken by other tasks. + } + else + { + // We could not obtain the mutex and can therefore not access + // the shared resource safely. + } + } + } + </pre> + * \defgroup xSemaphoreTakeRecursive xSemaphoreTakeRecursive + * \ingroup Semaphores + */ +#define xSemaphoreTakeRecursive( xMutex, xBlockTime ) xQueueTakeMutexRecursive( ( xMutex ), ( xBlockTime ) ) + + +/* + * xSemaphoreAltTake() is an alternative version of xSemaphoreTake(). + * + * The source code that implements the alternative (Alt) API is much + * simpler because it executes everything from within a critical section. + * This is the approach taken by many other RTOSes, but FreeRTOS.org has the + * preferred fully featured API too. The fully featured API has more + * complex code that takes longer to execute, but makes much less use of + * critical sections. Therefore the alternative API sacrifices interrupt + * responsiveness to gain execution speed, whereas the fully featured API + * sacrifices execution speed to ensure better interrupt responsiveness. + */ +#define xSemaphoreAltTake( xSemaphore, xBlockTime ) xQueueAltGenericReceive( ( xQueueHandle ) ( xSemaphore ), NULL, ( xBlockTime ), pdFALSE ) + +/** + * semphr. h + * <pre>xSemaphoreGive( xSemaphoreHandle xSemaphore )</pre> + * + * <i>Macro</i> to release a semaphore. The semaphore must have previously been + * created with a call to vSemaphoreCreateBinary(), xSemaphoreCreateMutex() or + * xSemaphoreCreateCounting(). and obtained using sSemaphoreTake(). + * + * This macro must not be used from an ISR. See xSemaphoreGiveFromISR () for + * an alternative which can be used from an ISR. + * + * This macro must also not be used on semaphores created using + * xSemaphoreCreateRecursiveMutex(). + * + * @param xSemaphore A handle to the semaphore being released. This is the + * handle returned when the semaphore was created. + * + * @return pdTRUE if the semaphore was released. pdFALSE if an error occurred. + * Semaphores are implemented using queues. An error can occur if there is + * no space on the queue to post a message - indicating that the + * semaphore was not first obtained correctly. + * + * Example usage: + <pre> + xSemaphoreHandle xSemaphore = NULL; + + void vATask( void * pvParameters ) + { + // Create the semaphore to guard a shared resource. + vSemaphoreCreateBinary( xSemaphore ); + + if( xSemaphore != NULL ) + { + if( xSemaphoreGive( xSemaphore ) != pdTRUE ) + { + // We would expect this call to fail because we cannot give + // a semaphore without first "taking" it! + } + + // Obtain the semaphore - don't block if the semaphore is not + // immediately available. + if( xSemaphoreTake( xSemaphore, ( portTickType ) 0 ) ) + { + // We now have the semaphore and can access the shared resource. + + // ... + + // We have finished accessing the shared resource so can free the + // semaphore. + if( xSemaphoreGive( xSemaphore ) != pdTRUE ) + { + // We would not expect this call to fail because we must have + // obtained the semaphore to get here. + } + } + } + } + </pre> + * \defgroup xSemaphoreGive xSemaphoreGive + * \ingroup Semaphores + */ +#define xSemaphoreGive( xSemaphore ) xQueueGenericSend( ( xQueueHandle ) ( xSemaphore ), NULL, semGIVE_BLOCK_TIME, queueSEND_TO_BACK ) + +/** + * semphr. h + * <pre>xSemaphoreGiveRecursive( xSemaphoreHandle xMutex )</pre> + * + * <i>Macro</i> to recursively release, or 'give', a mutex type semaphore. + * The mutex must have previously been created using a call to + * xSemaphoreCreateRecursiveMutex(); + * + * configUSE_RECURSIVE_MUTEXES must be set to 1 in FreeRTOSConfig.h for this + * macro to be available. + * + * This macro must not be used on mutexes created using xSemaphoreCreateMutex(). + * + * A mutex used recursively can be 'taken' repeatedly by the owner. The mutex + * doesn't become available again until the owner has called + * xSemaphoreGiveRecursive() for each successful 'take' request. For example, + * if a task successfully 'takes' the same mutex 5 times then the mutex will + * not be available to any other task until it has also 'given' the mutex back + * exactly five times. + * + * @param xMutex A handle to the mutex being released, or 'given'. This is the + * handle returned by xSemaphoreCreateMutex(); + * + * @return pdTRUE if the semaphore was given. + * + * Example usage: + <pre> + xSemaphoreHandle xMutex = NULL; + + // A task that creates a mutex. + void vATask( void * pvParameters ) + { + // Create the mutex to guard a shared resource. + xMutex = xSemaphoreCreateRecursiveMutex(); + } + + // A task that uses the mutex. + void vAnotherTask( void * pvParameters ) + { + // ... Do other things. + + if( xMutex != NULL ) + { + // See if we can obtain the mutex. If the mutex is not available + // wait 10 ticks to see if it becomes free. + if( xSemaphoreTakeRecursive( xMutex, ( portTickType ) 10 ) == pdTRUE ) + { + // We were able to obtain the mutex and can now access the + // shared resource. + + // ... + // For some reason due to the nature of the code further calls to + // xSemaphoreTakeRecursive() are made on the same mutex. In real + // code these would not be just sequential calls as this would make + // no sense. Instead the calls are likely to be buried inside + // a more complex call structure. + xSemaphoreTakeRecursive( xMutex, ( portTickType ) 10 ); + xSemaphoreTakeRecursive( xMutex, ( portTickType ) 10 ); + + // The mutex has now been 'taken' three times, so will not be + // available to another task until it has also been given back + // three times. Again it is unlikely that real code would have + // these calls sequentially, it would be more likely that the calls + // to xSemaphoreGiveRecursive() would be called as a call stack + // unwound. This is just for demonstrative purposes. + xSemaphoreGiveRecursive( xMutex ); + xSemaphoreGiveRecursive( xMutex ); + xSemaphoreGiveRecursive( xMutex ); + + // Now the mutex can be taken by other tasks. + } + else + { + // We could not obtain the mutex and can therefore not access + // the shared resource safely. + } + } + } + </pre> + * \defgroup xSemaphoreGiveRecursive xSemaphoreGiveRecursive + * \ingroup Semaphores + */ +#define xSemaphoreGiveRecursive( xMutex ) xQueueGiveMutexRecursive( ( xMutex ) ) + +/* + * xSemaphoreAltGive() is an alternative version of xSemaphoreGive(). + * + * The source code that implements the alternative (Alt) API is much + * simpler because it executes everything from within a critical section. + * This is the approach taken by many other RTOSes, but FreeRTOS.org has the + * preferred fully featured API too. The fully featured API has more + * complex code that takes longer to execute, but makes much less use of + * critical sections. Therefore the alternative API sacrifices interrupt + * responsiveness to gain execution speed, whereas the fully featured API + * sacrifices execution speed to ensure better interrupt responsiveness. + */ +#define xSemaphoreAltGive( xSemaphore ) xQueueAltGenericSend( ( xQueueHandle ) ( xSemaphore ), NULL, semGIVE_BLOCK_TIME, queueSEND_TO_BACK ) + +/** + * semphr. h + * <pre> + xSemaphoreGiveFromISR( + xSemaphoreHandle xSemaphore, + signed portBASE_TYPE *pxHigherPriorityTaskWoken + )</pre> + * + * <i>Macro</i> to release a semaphore. The semaphore must have previously been + * created with a call to vSemaphoreCreateBinary() or xSemaphoreCreateCounting(). + * + * Mutex type semaphores (those created using a call to xSemaphoreCreateMutex()) + * must not be used with this macro. + * + * This macro can be used from an ISR. + * + * @param xSemaphore A handle to the semaphore being released. This is the + * handle returned when the semaphore was created. + * + * @param pxHigherPriorityTaskWoken xSemaphoreGiveFromISR() will set + * *pxHigherPriorityTaskWoken to pdTRUE if giving the semaphore caused a task + * to unblock, and the unblocked task has a priority higher than the currently + * running task. If xSemaphoreGiveFromISR() sets this value to pdTRUE then + * a context switch should be requested before the interrupt is exited. + * + * @return pdTRUE if the semaphore was successfully given, otherwise errQUEUE_FULL. + * + * Example usage: + <pre> + \#define LONG_TIME 0xffff + \#define TICKS_TO_WAIT 10 + xSemaphoreHandle xSemaphore = NULL; + + // Repetitive task. + void vATask( void * pvParameters ) + { + for( ;; ) + { + // We want this task to run every 10 ticks of a timer. The semaphore + // was created before this task was started. + + // Block waiting for the semaphore to become available. + if( xSemaphoreTake( xSemaphore, LONG_TIME ) == pdTRUE ) + { + // It is time to execute. + + // ... + + // We have finished our task. Return to the top of the loop where + // we will block on the semaphore until it is time to execute + // again. Note when using the semaphore for synchronisation with an + // ISR in this manner there is no need to 'give' the semaphore back. + } + } + } + + // Timer ISR + void vTimerISR( void * pvParameters ) + { + static unsigned char ucLocalTickCount = 0; + static signed portBASE_TYPE xHigherPriorityTaskWoken; + + // A timer tick has occurred. + + // ... Do other time functions. + + // Is it time for vATask () to run? + xHigherPriorityTaskWoken = pdFALSE; + ucLocalTickCount++; + if( ucLocalTickCount >= TICKS_TO_WAIT ) + { + // Unblock the task by releasing the semaphore. + xSemaphoreGiveFromISR( xSemaphore, &xHigherPriorityTaskWoken ); + + // Reset the count so we release the semaphore again in 10 ticks time. + ucLocalTickCount = 0; + } + + if( xHigherPriorityTaskWoken != pdFALSE ) + { + // We can force a context switch here. Context switching from an + // ISR uses port specific syntax. Check the demo task for your port + // to find the syntax required. + } + } + </pre> + * \defgroup xSemaphoreGiveFromISR xSemaphoreGiveFromISR + * \ingroup Semaphores + */ +#define xSemaphoreGiveFromISR( xSemaphore, pxHigherPriorityTaskWoken ) xQueueGenericSendFromISR( ( xQueueHandle ) ( xSemaphore ), NULL, ( pxHigherPriorityTaskWoken ), queueSEND_TO_BACK ) + +/** + * semphr. h + * <pre>xSemaphoreHandle xSemaphoreCreateMutex( void )</pre> + * + * <i>Macro</i> that implements a mutex semaphore by using the existing queue + * mechanism. + * + * Mutexes created using this macro can be accessed using the xSemaphoreTake() + * and xSemaphoreGive() macros. The xSemaphoreTakeRecursive() and + * xSemaphoreGiveRecursive() macros should not be used. + * + * This type of semaphore uses a priority inheritance mechanism so a task + * 'taking' a semaphore MUST ALWAYS 'give' the semaphore back once the + * semaphore it is no longer required. + * + * Mutex type semaphores cannot be used from within interrupt service routines. + * + * See vSemaphoreCreateBinary() for an alternative implementation that can be + * used for pure synchronisation (where one task or interrupt always 'gives' the + * semaphore and another always 'takes' the semaphore) and from within interrupt + * service routines. + * + * @return xSemaphore Handle to the created mutex semaphore. Should be of type + * xSemaphoreHandle. + * + * Example usage: + <pre> + xSemaphoreHandle xSemaphore; + + void vATask( void * pvParameters ) + { + // Semaphore cannot be used before a call to xSemaphoreCreateMutex(). + // This is a macro so pass the variable in directly. + xSemaphore = xSemaphoreCreateMutex(); + + if( xSemaphore != NULL ) + { + // The semaphore was created successfully. + // The semaphore can now be used. + } + } + </pre> + * \defgroup vSemaphoreCreateMutex vSemaphoreCreateMutex + * \ingroup Semaphores + */ +#define xSemaphoreCreateMutex() xQueueCreateMutex() + + +/** + * semphr. h + * <pre>xSemaphoreHandle xSemaphoreCreateRecursiveMutex( void )</pre> + * + * <i>Macro</i> that implements a recursive mutex by using the existing queue + * mechanism. + * + * Mutexes created using this macro can be accessed using the + * xSemaphoreTakeRecursive() and xSemaphoreGiveRecursive() macros. The + * xSemaphoreTake() and xSemaphoreGive() macros should not be used. + * + * A mutex used recursively can be 'taken' repeatedly by the owner. The mutex + * doesn't become available again until the owner has called + * xSemaphoreGiveRecursive() for each successful 'take' request. For example, + * if a task successfully 'takes' the same mutex 5 times then the mutex will + * not be available to any other task until it has also 'given' the mutex back + * exactly five times. + * + * This type of semaphore uses a priority inheritance mechanism so a task + * 'taking' a semaphore MUST ALWAYS 'give' the semaphore back once the + * semaphore it is no longer required. + * + * Mutex type semaphores cannot be used from within interrupt service routines. + * + * See vSemaphoreCreateBinary() for an alternative implementation that can be + * used for pure synchronisation (where one task or interrupt always 'gives' the + * semaphore and another always 'takes' the semaphore) and from within interrupt + * service routines. + * + * @return xSemaphore Handle to the created mutex semaphore. Should be of type + * xSemaphoreHandle. + * + * Example usage: + <pre> + xSemaphoreHandle xSemaphore; + + void vATask( void * pvParameters ) + { + // Semaphore cannot be used before a call to xSemaphoreCreateMutex(). + // This is a macro so pass the variable in directly. + xSemaphore = xSemaphoreCreateRecursiveMutex(); + + if( xSemaphore != NULL ) + { + // The semaphore was created successfully. + // The semaphore can now be used. + } + } + </pre> + * \defgroup vSemaphoreCreateMutex vSemaphoreCreateMutex + * \ingroup Semaphores + */ +#define xSemaphoreCreateRecursiveMutex() xQueueCreateMutex() + +/** + * semphr. h + * <pre>xSemaphoreHandle xSemaphoreCreateCounting( unsigned portBASE_TYPE uxMaxCount, unsigned portBASE_TYPE uxInitialCount )</pre> + * + * <i>Macro</i> that creates a counting semaphore by using the existing + * queue mechanism. + * + * Counting semaphores are typically used for two things: + * + * 1) Counting events. + * + * In this usage scenario an event handler will 'give' a semaphore each time + * an event occurs (incrementing the semaphore count value), and a handler + * task will 'take' a semaphore each time it processes an event + * (decrementing the semaphore count value). The count value is therefore + * the difference between the number of events that have occurred and the + * number that have been processed. In this case it is desirable for the + * initial count value to be zero. + * + * 2) Resource management. + * + * In this usage scenario the count value indicates the number of resources + * available. To obtain control of a resource a task must first obtain a + * semaphore - decrementing the semaphore count value. When the count value + * reaches zero there are no free resources. When a task finishes with the + * resource it 'gives' the semaphore back - incrementing the semaphore count + * value. In this case it is desirable for the initial count value to be + * equal to the maximum count value, indicating that all resources are free. + * + * @param uxMaxCount The maximum count value that can be reached. When the + * semaphore reaches this value it can no longer be 'given'. + * + * @param uxInitialCount The count value assigned to the semaphore when it is + * created. + * + * @return Handle to the created semaphore. Null if the semaphore could not be + * created. + * + * Example usage: + <pre> + xSemaphoreHandle xSemaphore; + + void vATask( void * pvParameters ) + { + xSemaphoreHandle xSemaphore = NULL; + + // Semaphore cannot be used before a call to xSemaphoreCreateCounting(). + // The max value to which the semaphore can count should be 10, and the + // initial value assigned to the count should be 0. + xSemaphore = xSemaphoreCreateCounting( 10, 0 ); + + if( xSemaphore != NULL ) + { + // The semaphore was created successfully. + // The semaphore can now be used. + } + } + </pre> + * \defgroup xSemaphoreCreateCounting xSemaphoreCreateCounting + * \ingroup Semaphores + */ +#define xSemaphoreCreateCounting( uxMaxCount, uxInitialCount ) xQueueCreateCountingSemaphore( ( uxMaxCount ), ( uxInitialCount ) ) + + +#endif /* SEMAPHORE_H */ + + |