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<a href="#define-members">Macros</a> |
<a href="#func-members">Functions</a> </div>
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<div class="title">Semaphore Management</div> </div>
<div class="ingroups"><a class="el" href="group___c_m_s_i_s___r_t_o_s.html">CMSIS-RTOS API (RTX)</a></div></div><!--header-->
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<p>Control access to shared resources.
<a href="#details">More...</a></p>
<table class="memberdecls">
<tr class="heading"><td colspan="2"><h2 class="groupheader"><a name="define-members"></a>
Macros</h2></td></tr>
<tr class="memitem:ga7da4c7bfb340779c9fc7b321f5ab3e3a"><td class="memItemLeft" align="right" valign="top">#define </td><td class="memItemRight" valign="bottom"><a class="el" href="group___c_m_s_i_s___r_t_o_s___semaphore_mgmt.html#ga7da4c7bfb340779c9fc7b321f5ab3e3a">osFeature_Semaphore</a>   65535</td></tr>
<tr class="memdesc:ga7da4c7bfb340779c9fc7b321f5ab3e3a"><td class="mdescLeft"> </td><td class="mdescRight">Maximum count for <a class="el" href="group___c_m_s_i_s___r_t_o_s___semaphore_mgmt.html#ga97381e8e55cd47cec390bf57c96d6edb">osSemaphoreCreate</a> function. <a href="#ga7da4c7bfb340779c9fc7b321f5ab3e3a"></a><br/></td></tr>
<tr class="separator:ga7da4c7bfb340779c9fc7b321f5ab3e3a"><td class="memSeparator" colspan="2"> </td></tr>
<tr class="memitem:ga9e66fe361749071e5ab87826c43c2f1b"><td class="memItemLeft" align="right" valign="top">#define </td><td class="memItemRight" valign="bottom"><a class="el" href="group___c_m_s_i_s___r_t_o_s___semaphore_mgmt.html#ga9e66fe361749071e5ab87826c43c2f1b">osSemaphoreDef</a>(name)</td></tr>
<tr class="memdesc:ga9e66fe361749071e5ab87826c43c2f1b"><td class="mdescLeft"> </td><td class="mdescRight">Define a Semaphore object. <a href="#ga9e66fe361749071e5ab87826c43c2f1b"></a><br/></td></tr>
<tr class="separator:ga9e66fe361749071e5ab87826c43c2f1b"><td class="memSeparator" colspan="2"> </td></tr>
<tr class="memitem:ga03761ee8d2c3cd4544e18364ab301dac"><td class="memItemLeft" align="right" valign="top">#define </td><td class="memItemRight" valign="bottom"><a class="el" href="group___c_m_s_i_s___r_t_o_s___semaphore_mgmt.html#ga03761ee8d2c3cd4544e18364ab301dac">osSemaphore</a>(name)   &os_semaphore_def_##name</td></tr>
<tr class="memdesc:ga03761ee8d2c3cd4544e18364ab301dac"><td class="mdescLeft"> </td><td class="mdescRight">Access a Semaphore definition. <a href="#ga03761ee8d2c3cd4544e18364ab301dac"></a><br/></td></tr>
<tr class="separator:ga03761ee8d2c3cd4544e18364ab301dac"><td class="memSeparator" colspan="2"> </td></tr>
</table><table class="memberdecls">
<tr class="heading"><td colspan="2"><h2 class="groupheader"><a name="func-members"></a>
Functions</h2></td></tr>
<tr class="memitem:ga97381e8e55cd47cec390bf57c96d6edb"><td class="memItemLeft" align="right" valign="top"><a class="el" href="cmsis__os_8h.html#aa8968896c84094aa973683c84fa06f84">osSemaphoreId</a> </td><td class="memItemRight" valign="bottom"><a class="el" href="group___c_m_s_i_s___r_t_o_s___semaphore_mgmt.html#ga97381e8e55cd47cec390bf57c96d6edb">osSemaphoreCreate</a> (const <a class="el" href="structos_semaphore_def__t.html">osSemaphoreDef_t</a> *semaphore_def, int32_t count)</td></tr>
<tr class="memdesc:ga97381e8e55cd47cec390bf57c96d6edb"><td class="mdescLeft"> </td><td class="mdescRight">Create and Initialize a Semaphore object used for managing resources. <a href="#ga97381e8e55cd47cec390bf57c96d6edb"></a><br/></td></tr>
<tr class="separator:ga97381e8e55cd47cec390bf57c96d6edb"><td class="memSeparator" colspan="2"> </td></tr>
<tr class="memitem:gacc15b0fc8ce1167fe43da33042e62098"><td class="memItemLeft" align="right" valign="top">int32_t </td><td class="memItemRight" valign="bottom"><a class="el" href="group___c_m_s_i_s___r_t_o_s___semaphore_mgmt.html#gacc15b0fc8ce1167fe43da33042e62098">osSemaphoreWait</a> (<a class="el" href="cmsis__os_8h.html#aa8968896c84094aa973683c84fa06f84">osSemaphoreId</a> semaphore_id, uint32_t millisec)</td></tr>
<tr class="memdesc:gacc15b0fc8ce1167fe43da33042e62098"><td class="mdescLeft"> </td><td class="mdescRight">Wait until a Semaphore token becomes available. <a href="#gacc15b0fc8ce1167fe43da33042e62098"></a><br/></td></tr>
<tr class="separator:gacc15b0fc8ce1167fe43da33042e62098"><td class="memSeparator" colspan="2"> </td></tr>
<tr class="memitem:gab108914997c49e14d8ff1ae0d1988ca0"><td class="memItemLeft" align="right" valign="top"><a class="el" href="group___c_m_s_i_s___r_t_o_s___status.html#gae2e091fefc4c767117727bd5aba4d99e">osStatus</a> </td><td class="memItemRight" valign="bottom"><a class="el" href="group___c_m_s_i_s___r_t_o_s___semaphore_mgmt.html#gab108914997c49e14d8ff1ae0d1988ca0">osSemaphoreRelease</a> (<a class="el" href="cmsis__os_8h.html#aa8968896c84094aa973683c84fa06f84">osSemaphoreId</a> semaphore_id)</td></tr>
<tr class="memdesc:gab108914997c49e14d8ff1ae0d1988ca0"><td class="mdescLeft"> </td><td class="mdescRight">Release a Semaphore token. <a href="#gab108914997c49e14d8ff1ae0d1988ca0"></a><br/></td></tr>
<tr class="separator:gab108914997c49e14d8ff1ae0d1988ca0"><td class="memSeparator" colspan="2"> </td></tr>
<tr class="memitem:gabae2801ac2c096f6e8c69a264908f595"><td class="memItemLeft" align="right" valign="top"><a class="el" href="group___c_m_s_i_s___r_t_o_s___status.html#gae2e091fefc4c767117727bd5aba4d99e">osStatus</a> </td><td class="memItemRight" valign="bottom"><a class="el" href="group___c_m_s_i_s___r_t_o_s___semaphore_mgmt.html#gabae2801ac2c096f6e8c69a264908f595">osSemaphoreDelete</a> (<a class="el" href="cmsis__os_8h.html#aa8968896c84094aa973683c84fa06f84">osSemaphoreId</a> semaphore_id)</td></tr>
<tr class="memdesc:gabae2801ac2c096f6e8c69a264908f595"><td class="mdescLeft"> </td><td class="mdescRight">Delete a Semaphore that was created by <a class="el" href="group___c_m_s_i_s___r_t_o_s___semaphore_mgmt.html#ga97381e8e55cd47cec390bf57c96d6edb">osSemaphoreCreate</a>. <a href="#gabae2801ac2c096f6e8c69a264908f595"></a><br/></td></tr>
<tr class="separator:gabae2801ac2c096f6e8c69a264908f595"><td class="memSeparator" colspan="2"> </td></tr>
</table>
<a name="details" id="details"></a><h2 class="groupheader">Description</h2>
<p>The Semaphore Management function group is used to manage and protect access to shared resources. For example, with a Semaphore the access to a group of identical peripherals can be managed. The number of available resources is specified as parameter of the <a class="el" href="group___c_m_s_i_s___r_t_o_s___semaphore_mgmt.html#ga97381e8e55cd47cec390bf57c96d6edb">osSemaphoreCreate</a> function.</p>
<p>Each time a Semaphore token is obtained with <a class="el" href="group___c_m_s_i_s___r_t_o_s___semaphore_mgmt.html#gacc15b0fc8ce1167fe43da33042e62098">osSemaphoreWait</a> the semaphore count is decremented. When the semaphore count is 0, no Semaphore token can be obtained. Semaphores are released with <a class="el" href="group___c_m_s_i_s___r_t_o_s___semaphore_mgmt.html#gab108914997c49e14d8ff1ae0d1988ca0">osSemaphoreRelease</a>; this function increments the semaphore count.</p>
<div class="image">
<img src="Semaphore.png" alt="Semaphore.png"/>
<div class="caption">
CMSIS-RTOS Semaphore</div></div>
<h2 class="groupheader">Macro Definition Documentation</h2>
<a class="anchor" id="ga7da4c7bfb340779c9fc7b321f5ab3e3a"></a>
<div class="memitem">
<div class="memproto">
<table class="memname">
<tr>
<td class="memname">#define osFeature_Semaphore   65535</td>
</tr>
</table>
</div><div class="memdoc">
<p>CMSIS-RTOS RTX supports an index count up to 65535 for a semaphore . </p>
</div>
</div>
<a class="anchor" id="ga03761ee8d2c3cd4544e18364ab301dac"></a>
<div class="memitem">
<div class="memproto">
<table class="memname">
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<td class="memname">#define osSemaphore</td>
<td>(</td>
<td class="paramtype"> </td>
<td class="paramname">name</td><td>)</td>
<td>   &os_semaphore_def_##name</td>
</tr>
</table>
</div><div class="memdoc">
<p>Access to semaphore object for the functions <a class="el" href="group___c_m_s_i_s___r_t_o_s___semaphore_mgmt.html#ga97381e8e55cd47cec390bf57c96d6edb">osSemaphoreCreate</a>.</p>
<dl class="params"><dt>Parameters</dt><dd>
<table class="params">
<tr><td class="paramname">name</td><td>name of the semaphore object. </td></tr>
</table>
</dd>
</dl>
</div>
</div>
<a class="anchor" id="ga9e66fe361749071e5ab87826c43c2f1b"></a>
<div class="memitem">
<div class="memproto">
<table class="memname">
<tr>
<td class="memname">#define osSemaphoreDef</td>
<td>(</td>
<td class="paramtype"> </td>
<td class="paramname">name</td><td>)</td>
<td></td>
</tr>
</table>
</div><div class="memdoc">
<p>Define a semaphore object that is referenced by <a class="el" href="group___c_m_s_i_s___r_t_o_s___semaphore_mgmt.html#ga03761ee8d2c3cd4544e18364ab301dac">osSemaphore</a>.</p>
<dl class="params"><dt>Parameters</dt><dd>
<table class="params">
<tr><td class="paramname">name</td><td>name of the semaphore object. </td></tr>
</table>
</dd>
</dl>
</div>
</div>
<h2 class="groupheader">Function Documentation</h2>
<a class="anchor" id="ga97381e8e55cd47cec390bf57c96d6edb"></a>
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<td class="memname"><a class="el" href="cmsis__os_8h.html#aa8968896c84094aa973683c84fa06f84">osSemaphoreId</a> osSemaphoreCreate </td>
<td>(</td>
<td class="paramtype">const <a class="el" href="structos_semaphore_def__t.html">osSemaphoreDef_t</a> * </td>
<td class="paramname"><em>semaphore_def</em>, </td>
</tr>
<tr>
<td class="paramkey"></td>
<td></td>
<td class="paramtype">int32_t </td>
<td class="paramname"><em>count</em> </td>
</tr>
<tr>
<td></td>
<td>)</td>
<td></td><td></td>
</tr>
</table>
</div><div class="memdoc">
<dl class="params"><dt>Parameters</dt><dd>
<table class="params">
<tr><td class="paramdir">[in]</td><td class="paramname">semaphore_def</td><td>semaphore definition referenced with <a class="el" href="group___c_m_s_i_s___r_t_o_s___semaphore_mgmt.html#ga03761ee8d2c3cd4544e18364ab301dac">osSemaphore</a>. </td></tr>
<tr><td class="paramdir">[in]</td><td class="paramname">count</td><td>number of available resources. </td></tr>
</table>
</dd>
</dl>
<dl class="section return"><dt>Returns</dt><dd>semaphore ID for reference by other functions or NULL in case of error.</dd></dl>
<p>Create and initialize a Semaphore object that is used to manage access to shared resources. The parameter <em>count</em> specifies the number of available resources. The <em>count</em> value 1 creates a binary semaphore.</p>
<dl class="section note"><dt>Note</dt><dd><ul>
<li>The value <em>count</em> is only used to set the initial token count. The initial token count is not stored in memory (to save RAM as the RTX implementation tries to use as little resource as possible). Therefore no error is generated when <a class="el" href="group___c_m_s_i_s___r_t_o_s___semaphore_mgmt.html#gab108914997c49e14d8ff1ae0d1988ca0">osSemaphoreRelease</a> is used to release more tokens than specified with the initial token count.</li>
</ul>
</dd>
<dd>
- Cannot be called from <a class="el" href="_function_overview.html#CMSIS_RTOS_ISR_Calls">Interrupt Service Routines</a>.</dd></dl>
<p><b>Example</b> </p>
<div class="fragment"><div class="line"><span class="preprocessor">#include "<a class="code" href="cmsis__os_8h.html">cmsis_os.h</a>"</span></div>
<div class="line"> </div>
<div class="line"><a class="code" href="cmsis__os_8h.html#adfeb153a84a81309e2d958268197617f" title="Thread ID identifies the thread (pointer to a thread control block).">osThreadId</a> tid_thread1; <span class="comment">// ID for thread 1</span></div>
<div class="line"><a class="code" href="cmsis__os_8h.html#adfeb153a84a81309e2d958268197617f" title="Thread ID identifies the thread (pointer to a thread control block).">osThreadId</a> tid_thread2; <span class="comment">// ID for thread 2</span></div>
<div class="line"> </div>
<div class="line"><a class="code" href="cmsis__os_8h.html#aa8968896c84094aa973683c84fa06f84" title="Semaphore ID identifies the semaphore (pointer to a semaphore control block).">osSemaphoreId</a> semaphore; <span class="comment">// Semaphore ID</span></div>
<div class="line"><a class="code" href="group___c_m_s_i_s___r_t_o_s___semaphore_mgmt.html#ga9e66fe361749071e5ab87826c43c2f1b" title="Define a Semaphore object.">osSemaphoreDef</a>(semaphore); <span class="comment">// Semaphore definition</span></div>
<div class="line"> </div>
<div class="line"><span class="comment">//</span></div>
<div class="line"><span class="comment">// Thread 1 - High Priority - Active every 3ms</span></div>
<div class="line"><span class="comment">//</span></div>
<div class="line"><span class="keywordtype">void</span> thread1 (<span class="keywordtype">void</span> <span class="keyword">const</span> *argument) {</div>
<div class="line"> int32_t value;</div>
<div class="line"></div>
<div class="line"> <span class="keywordflow">while</span> (1) {</div>
<div class="line"> <a class="code" href="group___c_m_s_i_s___r_t_o_s___wait.html#ga02e19d5e723bfb06ba9324d625162255" title="Wait for Timeout (Time Delay).">osDelay</a>(3); <span class="comment">// Pass control to other tasks for 3ms</span></div>
<div class="line"> val = <a class="code" href="group___c_m_s_i_s___r_t_o_s___semaphore_mgmt.html#gacc15b0fc8ce1167fe43da33042e62098" title="Wait until a Semaphore token becomes available.">osSemaphoreWait</a> (semaphore, 1); <span class="comment">// Wait 1ms for the free semaphore</span></div>
<div class="line"> <span class="keywordflow">if</span> (val > 0) {</div>
<div class="line"> <span class="comment">// If there was no time-out the semaphore was acquired</span></div>
<div class="line"> : <span class="comment">// OK, the interface is free now, use it.</span></div>
<div class="line"> <a class="code" href="group___c_m_s_i_s___r_t_o_s___semaphore_mgmt.html#gab108914997c49e14d8ff1ae0d1988ca0" title="Release a Semaphore token.">osSemaphoreRelease</a> (semaphore); <span class="comment">// Return a token back to a semaphore</span></div>
<div class="line"> }</div>
<div class="line"> }</div>
<div class="line">}</div>
<div class="line"> </div>
<div class="line"><span class="comment">//</span></div>
<div class="line"><span class="comment">// Thread 2 - Normal Priority - looks for a free semaphore and uses</span></div>
<div class="line"><span class="comment">// the resource whenever it is available</span></div>
<div class="line"><span class="comment">//</span></div>
<div class="line"><span class="keywordtype">void</span> thread2 (<span class="keywordtype">void</span> <span class="keyword">const</span> *argument) {</div>
<div class="line"> <span class="keywordflow">while</span> (1) {</div>
<div class="line"> <a class="code" href="group___c_m_s_i_s___r_t_o_s___semaphore_mgmt.html#gacc15b0fc8ce1167fe43da33042e62098" title="Wait until a Semaphore token becomes available.">osSemaphoreWait</a> (semaphore, <a class="code" href="cmsis__os_8h.html#a9eb9a7a797a42e4b55eb171ecc609ddb" title="Timeout value.">osWaitForever</a>); <span class="comment">// Wait indefinitely for a free semaphore</span></div>
<div class="line"> <span class="comment">// OK, the interface is free now, use it.</span></div>
<div class="line"> :</div>
<div class="line"> <a class="code" href="group___c_m_s_i_s___r_t_o_s___semaphore_mgmt.html#gab108914997c49e14d8ff1ae0d1988ca0" title="Release a Semaphore token.">osSemaphoreRelease</a> (semaphore); <span class="comment">// Return a token back to a semaphore.</span></div>
<div class="line"> }</div>
<div class="line">}</div>
<div class="line"> </div>
<div class="line"><span class="comment">// Thread definitions </span></div>
<div class="line"><a class="code" href="group___c_m_s_i_s___r_t_o_s___thread_mgmt.html#gaee93d929beb350f16e5cc7fa602e229f" title="Create a Thread Definition with function, priority, and stack requirements.">osThreadDef</a>(thread1, <a class="code" href="group___c_m_s_i_s___r_t_o_s___thread_mgmt.html#ga7f2b42f1983b9107775ec2a1c69a849aa914433934143a9ba767e59577c56e6c2" title="priority: high">osPriorityHigh</a>, 1, 0);</div>
<div class="line"><a class="code" href="group___c_m_s_i_s___r_t_o_s___thread_mgmt.html#gaee93d929beb350f16e5cc7fa602e229f" title="Create a Thread Definition with function, priority, and stack requirements.">osThreadDef</a>(thread2, <a class="code" href="group___c_m_s_i_s___r_t_o_s___thread_mgmt.html#ga7f2b42f1983b9107775ec2a1c69a849aa45a2895ad30c79fb97de18cac7cc19f1" title="priority: normal (default)">osPriorityNormal</a>, 1, 0);</div>
<div class="line"> </div>
<div class="line"><span class="keywordtype">void</span> StartApplication (<span class="keywordtype">void</span>) {</div>
<div class="line"> semaphore = <a class="code" href="group___c_m_s_i_s___r_t_o_s___semaphore_mgmt.html#ga97381e8e55cd47cec390bf57c96d6edb" title="Create and Initialize a Semaphore object used for managing resources.">osSemaphoreCreate</a>(<a class="code" href="group___c_m_s_i_s___r_t_o_s___semaphore_mgmt.html#ga03761ee8d2c3cd4544e18364ab301dac" title="Access a Semaphore definition.">osSemaphore</a>(semaphore), 1);</div>
<div class="line"></div>
<div class="line"> tid_thread1 = <a class="code" href="group___c_m_s_i_s___r_t_o_s___thread_mgmt.html#gac59b5713cb083702dce759c73fd90dff" title="Create a thread and add it to Active Threads and set it to state READY.">osThreadCreate</a>(<a class="code" href="group___c_m_s_i_s___r_t_o_s___thread_mgmt.html#gaf0c7c6b5e09f8be198312144b5c9e453" title="Access a Thread definition.">osThread</a>(thread1), NULL);</div>
<div class="line"> tid_thread2 = <a class="code" href="group___c_m_s_i_s___r_t_o_s___thread_mgmt.html#gac59b5713cb083702dce759c73fd90dff" title="Create a thread and add it to Active Threads and set it to state READY.">osThreadCreate</a>(<a class="code" href="group___c_m_s_i_s___r_t_o_s___thread_mgmt.html#gaf0c7c6b5e09f8be198312144b5c9e453" title="Access a Thread definition.">osThread</a>(thread2), NULL);</div>
<div class="line"> :</div>
<div class="line">}</div>
</div><!-- fragment -->
</div>
</div>
<a class="anchor" id="gabae2801ac2c096f6e8c69a264908f595"></a>
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<table class="memname">
<tr>
<td class="memname"><a class="el" href="group___c_m_s_i_s___r_t_o_s___status.html#gae2e091fefc4c767117727bd5aba4d99e">osStatus</a> osSemaphoreDelete </td>
<td>(</td>
<td class="paramtype"><a class="el" href="cmsis__os_8h.html#aa8968896c84094aa973683c84fa06f84">osSemaphoreId</a> </td>
<td class="paramname"><em>semaphore_id</em></td><td>)</td>
<td></td>
</tr>
</table>
</div><div class="memdoc">
<dl class="params"><dt>Parameters</dt><dd>
<table class="params">
<tr><td class="paramdir">[in]</td><td class="paramname">semaphore_id</td><td>semaphore object referenced with <a class="el" href="group___c_m_s_i_s___r_t_o_s___semaphore_mgmt.html#ga97381e8e55cd47cec390bf57c96d6edb">osSemaphoreCreate</a>. </td></tr>
</table>
</dd>
</dl>
<dl class="section return"><dt>Returns</dt><dd>status code that indicates the execution status of the function.</dd></dl>
<p>Delete a Semaphore object. The function releases internal memory obtained for Semaphore handling. After this call the <em>semaphore_id</em> is no longer valid and cannot be used. The Semaphore may be created again using the function <a class="el" href="group___c_m_s_i_s___r_t_o_s___semaphore_mgmt.html#ga97381e8e55cd47cec390bf57c96d6edb">osSemaphoreCreate</a>.</p>
<p><b><a class="el" href="group___c_m_s_i_s___r_t_o_s___status.html">Status and Error Codes</a></b><br/>
</p>
<ul>
<li><em>osOK:</em> the semaphore object has been deleted.</li>
<li><em>osErrorISR:</em> <a class="el" href="group___c_m_s_i_s___r_t_o_s___semaphore_mgmt.html#gabae2801ac2c096f6e8c69a264908f595">osSemaphoreDelete</a> cannot be called from interrupt service routines.</li>
<li><em>osErrorResource:</em> the semaphore object could not be deleted.</li>
<li><em>osErrorParameter:</em> the parameter <em>semaphore_id</em> is incorrect.</li>
</ul>
<dl class="section note"><dt>Note</dt><dd>Cannot be called from <a class="el" href="_function_overview.html#CMSIS_RTOS_ISR_Calls">Interrupt Service Routines</a>. </dd></dl>
</div>
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<td class="memname"><a class="el" href="group___c_m_s_i_s___r_t_o_s___status.html#gae2e091fefc4c767117727bd5aba4d99e">osStatus</a> osSemaphoreRelease </td>
<td>(</td>
<td class="paramtype"><a class="el" href="cmsis__os_8h.html#aa8968896c84094aa973683c84fa06f84">osSemaphoreId</a> </td>
<td class="paramname"><em>semaphore_id</em></td><td>)</td>
<td></td>
</tr>
</table>
</div><div class="memdoc">
<dl class="params"><dt>Parameters</dt><dd>
<table class="params">
<tr><td class="paramdir">[in]</td><td class="paramname">semaphore_id</td><td>semaphore object referenced with <a class="el" href="group___c_m_s_i_s___r_t_o_s___semaphore_mgmt.html#ga97381e8e55cd47cec390bf57c96d6edb">osSemaphoreCreate</a>. </td></tr>
</table>
</dd>
</dl>
<dl class="section return"><dt>Returns</dt><dd>status code that indicates the execution status of the function.</dd></dl>
<p>Release a Semaphore token. This increments the count of available semaphore tokens.</p>
<dl class="section note"><dt>Note</dt><dd><a class="el" href="_function_overview.html#CMSIS_RTOS_ISR_Calls">Interrupt Service Routines</a> can call this function.</dd></dl>
<p><b><a class="el" href="group___c_m_s_i_s___r_t_o_s___status.html">Status and Error Codes</a></b><br/>
</p>
<ul>
<li><em>osOK:</em> the semaphore has been released.</li>
<li><em>osErrorResource:</em> all tokens have already been released.</li>
<li><em>osErrorParameter:</em> the parameter <em>semaphore_id</em> is incorrect. </li>
</ul>
</div>
</div>
<a class="anchor" id="gacc15b0fc8ce1167fe43da33042e62098"></a>
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<td class="memname">int32_t osSemaphoreWait </td>
<td>(</td>
<td class="paramtype"><a class="el" href="cmsis__os_8h.html#aa8968896c84094aa973683c84fa06f84">osSemaphoreId</a> </td>
<td class="paramname"><em>semaphore_id</em>, </td>
</tr>
<tr>
<td class="paramkey"></td>
<td></td>
<td class="paramtype">uint32_t </td>
<td class="paramname"><em>millisec</em> </td>
</tr>
<tr>
<td></td>
<td>)</td>
<td></td><td></td>
</tr>
</table>
</div><div class="memdoc">
<dl class="params"><dt>Parameters</dt><dd>
<table class="params">
<tr><td class="paramdir">[in]</td><td class="paramname">semaphore_id</td><td>semaphore object referenced with <a class="el" href="group___c_m_s_i_s___r_t_o_s___semaphore_mgmt.html#ga97381e8e55cd47cec390bf57c96d6edb">osSemaphoreCreate</a>. </td></tr>
<tr><td class="paramdir">[in]</td><td class="paramname">millisec</td><td><a class="el" href="_function_overview.html#CMSIS_RTOS_TimeOutValue">Timout Value</a> or 0 in case of no time-out. </td></tr>
</table>
</dd>
</dl>
<dl class="section return"><dt>Returns</dt><dd>number of available tokens, or -1 in case of incorrect parameters.</dd></dl>
<p>Wait until a Semaphore token becomes available. When no Semaphore token is available, the function waits for the time specified with the parameter <em>millisec</em>.</p>
<p>The argument <em>millisec</em> specifies how long the system waits for a Semaphore token to become available. While the system waits the thread that is calling this function is put into the state <b>WAITING</b>. The <em>millisec</em> timeout can have the following values:</p>
<ul>
<li>when <em>millisec</em> is 0, the function returns instantly.</li>
<li>when <em>millisec</em> is set to <b>osWaitForever</b> the function will wait for an infinite time until the Semaphore token becomes available.</li>
<li>all other values specify a time in millisecond for a timeout.</li>
</ul>
<p>The return value indicates the number of available tokens (the semaphore count value). If 0 is returned, then no semaphore was available.</p>
<dl class="section note"><dt>Note</dt><dd>Cannot be called from <a class="el" href="_function_overview.html#CMSIS_RTOS_ISR_Calls">Interrupt Service Routines</a>. </dd></dl>
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