Espressif ESP32-S2 Programming Manual page 914

Chapter 2. API Reference
// Rest of task code goes
}
Return If the semaphore is created then a handle to the created semaphore is returned. If pxSemaphoreBuffer
is NULL then NULL is returned.
Parameters
• pxStaticSemaphore: Must point to a variable of type StaticSemaphore_t, which will then be
used to hold the semaphore's data structure, removing the need for the memory to be allocated
dynamically.
xSemaphoreTake(xSemaphore, xBlockTime)
Macro to obtain a semaphore. The semaphore must have previously been created with a call to xSemaphoreCre-
ateBinary(), 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.
portTICK_PERIOD_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 IN-
CLUDE_vTaskSuspend is set to 1 in FreeRTOSConfig.h).
Example usage:
SemaphoreHandle_t xSemaphore
// A task that creates a
void vATask( void
{
// Create the semaphore to guard a shared
vSemaphoreCreateBinary( xSemaphore );
}
// A task that uses the
void vAnotherTask( void
{
// ... Do other
if( xSemaphore
{
// See if
// wait 10
if( xSemaphoreTake( xSemaphore, ( TickType_t )
{
// We were able to obtain the semaphore
// shared
// ...
// We have finished accessing the shared
// semaphore.
xSemaphoreGive( xSemaphore );
}
else
{
// We could
// the shared resource
}
}
}
Return pdTRUE if the semaphore was obtained. pdFALSE if xBlockTime expired without the semaphore
Espressif Systems
here.
= NULL;
semaphore.
* pvParameters )
semaphore.
* pvParameters )
things.
!= NULL )
we can obtain the semaphore.
ticks to see if it becomes
resource.
not obtain the semaphore
safely.
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resource.
If the semaphore
free.
10
and can now access the
resource.
and can therefore
903
(continued from previous page)
The macro
is not available
) == pdTRUE )
Release the
not access
Release v4.4