semphr.h File Reference

#include "queue.h"

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Macros
#define	semBINARY_SEMAPHORE_QUEUE_LENGTH   ( ( uint8_t ) 1U )
#define	semSEMAPHORE_QUEUE_ITEM_LENGTH   ( ( uint8_t ) 0U )
#define	semGIVE_BLOCK_TIME   ( ( TickType_t ) 0U )
#define	xSemaphoreTake(xSemaphore, xBlockTime)
#define	xSemaphoreGive(xSemaphore)
#define	xSemaphoreGiveFromISR(xSemaphore, pxHigherPriorityTaskWoken)
#define	xSemaphoreTakeFromISR(xSemaphore, pxHigherPriorityTaskWoken)
#define	vSemaphoreDelete(xSemaphore)
#define	uxSemaphoreGetCount(xSemaphore)
#define	uxSemaphoreGetCountFromISR(xSemaphore)

Typedefs
typedef QueueHandle_t	SemaphoreHandle_t

Macro Definition Documentation

semBINARY_SEMAPHORE_QUEUE_LENGTH

#define semBINARY_SEMAPHORE_QUEUE_LENGTH   ( ( uint8_t ) 1U )

semGIVE_BLOCK_TIME

#define semGIVE_BLOCK_TIME   ( ( TickType_t ) 0U )

semSEMAPHORE_QUEUE_ITEM_LENGTH

#define semSEMAPHORE_QUEUE_ITEM_LENGTH   ( ( uint8_t ) 0U )

uxSemaphoreGetCount

#define uxSemaphoreGetCount

(

xSemaphore

)

Value:

uxQueueMessagesWaiting( ( QueueHandle_t ) ( xSemaphore ) )

semphr.h

TaskHandle_t xSemaphoreGetMutexHolder( SemaphoreHandle_t xMutex );

If xMutex is indeed a mutex type semaphore, return the current mutex holder. If xMutex is not a mutex type semaphore, or the mutex is available (not held by a task), return NULL.

Note: This is a good way of determining if the calling task is the mutex holder, but not a good way of determining the identity of the mutex holder as the holder may change between the function exiting and the returned value being tested. semphr.h

TaskHandle_t xSemaphoreGetMutexHolderFromISR( SemaphoreHandle_t xMutex );

If xMutex is indeed a mutex type semaphore, return the current mutex holder. If xMutex is not a mutex type semaphore, or the mutex is available (not held by a task), return NULL. semphr.h

UBaseType_t uxSemaphoreGetCount( SemaphoreHandle_t xSemaphore );

If the semaphore is a counting semaphore then uxSemaphoreGetCount() returns its current count value. If the semaphore is a binary semaphore then uxSemaphoreGetCount() returns 1 if the semaphore is available, and 0 if the semaphore is not available.

uxSemaphoreGetCountFromISR

#define uxSemaphoreGetCountFromISR

(

xSemaphore

)

Value:

uxQueueMessagesWaitingFromISR( ( QueueHandle_t ) ( xSemaphore ) )

semphr.h

UBaseType_t uxSemaphoreGetCountFromISR( SemaphoreHandle_t xSemaphore );

If the semaphore is a counting semaphore then uxSemaphoreGetCountFromISR() returns its current count value. If the semaphore is a binary semaphore then uxSemaphoreGetCountFromISR() returns 1 if the semaphore is available, and 0 if the semaphore is not available.

vSemaphoreDelete

#define vSemaphoreDelete

(

xSemaphore

)

Value:

vQueueDelete( ( QueueHandle_t ) ( xSemaphore ) )

xSemaphoreGive

#define xSemaphoreGive

(

xSemaphore

)

Value:

xQueueGenericSend( ( QueueHandle_t ) ( xSemaphore ), NULL, semGIVE_BLOCK_TIME, queueSEND_TO_BACK )

xSemaphoreGiveFromISR

#define xSemaphoreGiveFromISR	(		xSemaphore,
			pxHigherPriorityTaskWoken )

Value:

xQueueGiveFromISR( ( QueueHandle_t ) ( xSemaphore ), ( pxHigherPriorityTaskWoken ) )

xSemaphoreTake

#define xSemaphoreTake	(		xSemaphore,
			xBlockTime )

Value:

xQueueSemaphoreTake( ( xSemaphore ), ( xBlockTime ) )

xSemaphoreTakeFromISR

#define xSemaphoreTakeFromISR	(		xSemaphore,
			pxHigherPriorityTaskWoken )

Value:

xQueueReceiveFromISR( ( QueueHandle_t ) ( xSemaphore ), NULL, ( pxHigherPriorityTaskWoken ) )

semphr. h

xSemaphoreTakeFromISR(
                       SemaphoreHandle_t xSemaphore,
                       BaseType_t *pxHigherPriorityTaskWoken
                   );

Macro to take a semaphore from an ISR. The semaphore must have previously been created with a call to xSemaphoreCreateBinary() 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, however taking a semaphore from an ISR is not a common operation. It is likely to only be useful when taking a counting semaphore when an interrupt is obtaining an object from a resource pool (when the semaphore count indicates the number of resources available).

Parameters

xSemaphore	A handle to the semaphore being taken. This is the handle returned when the semaphore was created.
pxHigherPriorityTaskWoken	xSemaphoreTakeFromISR() will set *pxHigherPriorityTaskWoken to pdTRUE if taking the semaphore caused a task to unblock, and the unblocked task has a priority higher than the currently running task. If xSemaphoreTakeFromISR() sets this value to pdTRUE then a context switch should be requested before the interrupt is exited.

Returns

pdTRUE if the semaphore was successfully taken, otherwise pdFALSE

Typedef Documentation

SemaphoreHandle_t

typedef QueueHandle_t SemaphoreHandle_t