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<p>semphr. h </p><pre>SemaphoreHandle_t xSemaphoreCreateBinary( void )</pre><p>Creates a new binary semaphore instance, and returns a handle by which the new semaphore can be referenced.</p>
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<p>In many usage scenarios it is faster and more memory efficient to use a direct to task notification in place of a binary semaphore! <a href="http://www.freertos.org/RTOS-task-notifications.html">http://www.freertos.org/RTOS-task-notifications.html</a></p>
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<p>Internally, within the FreeRTOS implementation, binary semaphores use a block of memory, in which the semaphore structure is stored. If a binary semaphore is created using xSemaphoreCreateBinary() then the required memory is automatically dynamically allocated inside the xSemaphoreCreateBinary() function. (see <a href="http://www.freertos.org/a00111.html">http://www.freertos.org/a00111.html</a>). If a binary semaphore is created using xSemaphoreCreateBinaryStatic() then the application writer must provide the memory. xSemaphoreCreateBinaryStatic() therefore allows a binary semaphore to be created without using any dynamic memory allocation.</p>
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<p>The old vSemaphoreCreateBinary() macro is now deprecated in favour of this xSemaphoreCreateBinary() function. Note that binary semaphores created using the vSemaphoreCreateBinary() macro are created in a state such that the first call to 'take' the semaphore would pass, whereas binary semaphores created using xSemaphoreCreateBinary() are created in a state such that the the semaphore must first be 'given' before it can be 'taken'.</p>
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<p>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().</p>
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<dl class="section return"><dt>Returns</dt><dd>Handle to the created semaphore, or NULL if the memory required to hold the semaphore's data structures could not be allocated.</dd></dl>
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<p>Example usage: </p><pre>
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SemaphoreHandle_t xSemaphore = NULL;</pre><pre>void vATask( void * pvParameters )
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{
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// Semaphore cannot be used before a call to xSemaphoreCreateBinary().
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// This is a macro so pass the variable in directly.
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xSemaphore = xSemaphoreCreateBinary();</pre><pre> if( xSemaphore != NULL )
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{
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// The semaphore was created successfully.
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// The semaphore can now be used.
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}
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}
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