Chapter 2. API Reference
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else
{
// We could not obtain the mutex and can therefore not access
// the shared resource safely.
}
}
}
Return pdTRUE if the semaphore was given.
Parameters
• xMutex: A handle to the mutex being released, or ‘given’. This is the handle returned by
xSemaphoreCreateMutex();
xSemaphoreGiveFromISR(xSemaphore, pxHigherPriorityTaskWoken)
Macro to release a semaphore. 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.
Example usage:
#define LONG_TIME 0xffff
#define TICKS_TO_WAIT 10
SemaphoreHandle_t 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 uint8_t ucLocalTickCount = 0;
static BaseType_t xHigherPriorityTaskWoken;
// A timer tick has occurred.
// ... Do other time functions.
// Is it time for vATask () to run?
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