?? void4.htm
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either by an ISR or by another task.<span style="mso-spacerun: yes">
</span>The messages received are pointer size variables and their use is
application specific.<span style="mso-spacerun: yes"> </span>If a at
least one message is present at the queue when </span><span class=CodeInText><span
lang=EN-US style='font-size:12.0pt;font-family:"Courier New"'>OSQPend()</span></span><span
lang=EN-US> is called, the message is retrieved and returned to the
caller.<span style="mso-spacerun: yes"> </span>If no message is present
at the queue, </span><span class=CodeInText><span lang=EN-US style='font-size:
12.0pt;font-family:"Courier New"'>OSQPend()</span></span><span lang=EN-US> will
suspend the current task until either a message is received or a user specified
timeout expires.<span style="mso-spacerun: yes"> </span>If a message is
sent to the queue and multiple tasks are waiting for such a message then,
µC/OS-II will resume the highest priority task that is waiting.<span
style="mso-spacerun: yes"> </span>A pended task that has been suspended
with </span><span class=CodeInText><span lang=EN-US style='font-size:12.0pt;
font-family:"Courier New"'>OSTaskSuspend()</span></span><span lang=EN-US> can
receive a message.<span style="mso-spacerun: yes"> </span>The task will,
however, remain suspended until the task is resumed by calling </span><span
class=CodeInText><span lang=EN-US style='font-size:12.0pt;font-family:"Courier New"'>OSTaskResume()</span></span><span
lang=EN-US>.</span></p>
<p class=NewSectionPara><span lang=EN-US><![if !supportEmptyParas]> <![endif]><o:p></o:p></span></p>
<p class=NewSectionPara><b><span lang=EN-US>Arguments<o:p></o:p></span></b></p>
<p class=Descript><span class=CodeInText><span lang=EN-US style='font-size:
12.0pt;font-family:"Courier New"'>pevent</span></span><span lang=EN-US> is a
pointer to the queue where the messages are to be received from.<span
style="mso-spacerun: yes"> </span>This pointer is returned to your
application when the queue is created (see </span><b><span lang=EN-US
style='font-family:"Courier New"'>OSQCreate()</span></b><span lang=EN-US>).</span></p>
<p class=Descript><b><span lang=EN-US style='font-family:"Courier New"'>timeout</span></b><span
lang=EN-US> is used to allow the task to resume execution if a message is not
received from the mailbox within the specified number of clock ticks.<span
style="mso-spacerun: yes"> </span>A </span><b><span lang=EN-US
style='font-family:"Courier New"'>timeout</span></b><span lang=EN-US> value of
0 indicates that the task desires to wait forever for the message.<span
style="mso-spacerun: yes"> </span>The maximum </span><b><span lang=EN-US
style='font-family:"Courier New"'>timeout</span></b><span lang=EN-US> is 65535
clock ticks.<span style="mso-spacerun: yes"> </span>The timeout value is
not synchronized with the clock tick.<span style="mso-spacerun: yes">
</span>The timeout count starts being decremented on the next clock tick which
could potentially occur immediately.</span></p>
<p class=Descript><span class=CodeInText><span lang=EN-US style='font-size:
12.0pt;font-family:"Courier New"'>err</span></span><span lang=EN-US> is a
pointer to a variable which will be used to hold an error code.<span
style="mso-spacerun: yes"> </span></span><b><span lang=EN-US
style='font-family:"Courier New"'>OSQPend()</span></b><span lang=EN-US> sets </span><b><span
lang=EN-US style='font-family:"Courier New"'>*err</span></b><span lang=EN-US>
to either:</span></p>
<p class=Descript style='margin-left:54.0pt;text-indent:-18.0pt'><span
lang=EN-US>1) <span style='mso-tab-count:1'> </span></span><b><span
lang=EN-US style='font-family:"Courier New"'>OS_NO_ERR</span></b><span
lang=EN-US>, a message was received</span></p>
<p class=Descript style='margin-left:54.0pt;text-indent:-18.0pt'><span
lang=EN-US>2) <span style='mso-tab-count:1'> </span></span><b><span
lang=EN-US style='font-family:"Courier New"'>OS_TIMEOUT</span></b><span
lang=EN-US>, a message was not received within the specified timeout</span></p>
<p class=Descript style='margin-left:54.0pt;text-indent:-18.0pt'><span
lang=EN-US>3) <span style='mso-tab-count:1'> </span></span><b><span
lang=EN-US style='font-family:"Courier New"'>OS_ERR_PEND_ISR</span></b><span
lang=EN-US>, you called this function from an ISR and µC/OS-II would have to
suspend the ISR.<span style="mso-spacerun: yes"> </span>In general, you
should not call </span><b><span lang=EN-US style='font-family:"Courier New"'>OSQPend()</span></b><span
lang=EN-US>.<span style="mso-spacerun: yes"> </span>µC/OS-II checks for
this situation in case you do anyway. </span></p>
<p class=NewSectionPara><span lang=EN-US><![if !supportEmptyParas]> <![endif]><o:p></o:p></span></p>
<p class=NewSectionPara><b><span lang=EN-US>Returned Value<o:p></o:p></span></b></p>
<p class=Descript><b><span lang=EN-US style='font-family:"Courier New"'>OSQPend()</span></b><span
lang=EN-US> returns a message sent by either a task or an ISR and </span><b><span
lang=EN-US style='font-family:"Courier New"'>*err</span></b><span lang=EN-US>
is set to </span><b><span lang=EN-US style='font-family:"Courier New"'>OS_NO_ERR</span></b><span
lang=EN-US>.<span style="mso-spacerun: yes"> </span>If a timeout
occurred, </span><b><span lang=EN-US style='font-family:"Courier New"'>OSQPend()</span></b><span
lang=EN-US> returns a </span><b><span lang=EN-US style='font-family:"Courier New"'>NULL</span></b><span
lang=EN-US> pointer and sets </span><b><span lang=EN-US style='font-family:
"Courier New"'>*err</span></b><span lang=EN-US> to </span><b><span lang=EN-US
style='font-family:"Courier New"'>OS_TIMEOUT</span></b><span lang=EN-US>.</span></p>
<p class=NewSectionPara><span lang=EN-US><![if !supportEmptyParas]> <![endif]><o:p></o:p></span></p>
<p class=NewSectionPara><b><span lang=EN-US>Notes/Warnings<o:p></o:p></span></b></p>
<p class=Descript><span lang=EN-US>Queues must be created before they are used.
</span></p>
<p class=Descript><span lang=EN-US><![if !supportEmptyParas]> <![endif]><o:p></o:p></span></p>
<p class=NewSectionPara><b><span lang=EN-US>Example<o:p></o:p></span></b></p>
<div style='border:solid #999999 1.5pt;padding:1.0pt 1.0pt 15.0pt 1.0pt;
background:#F2F2F2;mso-shading:windowtext;mso-pattern:gray-5 auto'>
<p class=CodeSeg style='border:none;mso-border-alt:solid #999999 1.5pt;
padding:0cm;mso-padding-alt:1.0pt 1.0pt 15.0pt 1.0pt'><span lang=EN-US><span
style='mso-tab-count:1'> </span>OS_EVENT *CommQ;</span></p>
<p class=CodeSeg style='border:none;mso-border-alt:solid #999999 1.5pt;
padding:0cm;mso-padding-alt:1.0pt 1.0pt 15.0pt 1.0pt'><span lang=EN-US><span
style='mso-tab-count:1'> </span>void CommTask(void *data)</span></p>
<p class=CodeSeg style='border:none;mso-border-alt:solid #999999 1.5pt;
padding:0cm;mso-padding-alt:1.0pt 1.0pt 15.0pt 1.0pt'><span lang=EN-US><span
style='mso-tab-count:1'> </span>{</span></p>
<p class=CodeSeg style='border:none;mso-border-alt:solid #999999 1.5pt;
padding:0cm;mso-padding-alt:1.0pt 1.0pt 15.0pt 1.0pt'><span lang=EN-US><span
style="mso-spacerun: yes"> </span>INT8U<span
style="mso-spacerun: yes"> </span>err;</span></p>
<p class=CodeSeg style='border:none;mso-border-alt:solid #999999 1.5pt;
padding:0cm;mso-padding-alt:1.0pt 1.0pt 15.0pt 1.0pt'><span lang=EN-US><span
style="mso-spacerun: yes"> </span>void<span
style="mso-spacerun: yes"> </span>*msg;</span></p>
<p class=CodeSeg style='border:none;mso-border-alt:solid #999999 1.5pt;
padding:0cm;mso-padding-alt:1.0pt 1.0pt 15.0pt 1.0pt'><span lang=EN-US><span
style="mso-spacerun: yes"> </span>pdata = pdata;</span></p>
<p class=CodeSeg style='border:none;mso-border-alt:solid #999999 1.5pt;
padding:0cm;mso-padding-alt:1.0pt 1.0pt 15.0pt 1.0pt'><span lang=EN-US><span
style="mso-spacerun: yes"> </span>for (;;) {</span></p>
<p class=CodeSeg style='border:none;mso-border-alt:solid #999999 1.5pt;
padding:0cm;mso-padding-alt:1.0pt 1.0pt 15.0pt 1.0pt'><span lang=EN-US><span
style='mso-tab-count:3'> </span>.</span></p>
<p class=CodeSeg style='border:none;mso-border-alt:solid #999999 1.5pt;
padding:0cm;mso-padding-alt:1.0pt 1.0pt 15.0pt 1.0pt'><span lang=EN-US><span
style='mso-tab-count:3'> </span>msg
= OSQPend(CommQ, 100, &err);</span></p>
<p class=CodeSeg style='border:none;mso-border-alt:solid #999999 1.5pt;
padding:0cm;mso-padding-alt:1.0pt 1.0pt 15.0pt 1.0pt'><span lang=EN-US><span
style="mso-spacerun: yes">
</span>if (err == OS_NO_ERR) {</span></p>
<p class=CodeSeg style='border:none;mso-border-alt:solid #999999 1.5pt;
padding:0cm;mso-padding-alt:1.0pt 1.0pt 15.0pt 1.0pt'><span lang=EN-US><span
style="mso-spacerun:
yes">
</span>.<span style="mso-spacerun: yes">
</span>/* Message received within 100 ticks!<span style="mso-spacerun:
yes"> </span>*/</span></p>
<p class=CodeSeg style='border:none;mso-border-alt:solid #999999 1.5pt;
padding:0cm;mso-padding-alt:1.0pt 1.0pt 15.0pt 1.0pt'><span lang=EN-US><span
style="mso-spacerun: yes">
</span>} else {</span></p>
<p class=CodeSeg style='border:none;mso-border-alt:solid #999999 1.5pt;
padding:0cm;mso-padding-alt:1.0pt 1.0pt 15.0pt 1.0pt'><span lang=EN-US><span
style="mso-spacerun:
yes">
</span>.<span style="mso-spacerun: yes">
</span>/* Message not received, must have timed out<span style="mso-spacerun:
yes"> </span>*/</span></p>
<p class=CodeSeg style='border:none;mso-border-alt:solid #999999 1.5pt;
padding:0cm;mso-padding-alt:1.0pt 1.0pt 15.0pt 1.0pt'><span lang=EN-US><span
style="mso-spacerun: yes">
</span>}</span></p>
<p class=CodeSeg style='border:none;mso-border-alt:solid #999999 1.5pt;
padding:0cm;mso-padding-alt:1.0pt 1.0pt 15.0pt 1.0pt'><span lang=EN-US><span
style='mso-tab-count:3'> </span>.</span></p>
<p class=CodeSeg style='text-indent:30.75pt;border:none;mso-border-alt:solid #999999 1.5pt;
padding:0cm;mso-padding-alt:1.0pt 1.0pt 15.0pt 1.0pt'><span lang=EN-US>}</span><span
lang=EN-US style='mso-fareast-language:ZH-CN'><o:p></o:p></span></p>
<p class=CodeSeg style='border:none;mso-border-alt:solid #999999 1.5pt;
padding:0cm;mso-padding-alt:1.0pt 1.0pt 15.0pt 1.0pt'><span lang=EN-US>}</span></p>
</div>
<p class=Code><span lang=EN-US style='font-size:9.0pt'><![if !supportEmptyParas]> <![endif]><o:p></o:p></span></p>
<p class=Code><span lang=EN-US style='font-size:9.0pt'><![if !supportEmptyParas]> <![endif]><o:p></o:p></span></p>
</div>
<span lang=EN-US style='font-size:10.5pt;mso-bidi-font-size:12.0pt;font-family:
"Times New Roman";mso-fareast-font-family:宋體;mso-font-kerning:1.0pt;mso-ansi-language:
EN-US;mso-fareast-language:ZH-CN;mso-bidi-language:AR-SA'><br clear=all
style='page-break-before:always;mso-break-type:section-break'>
</span>
<div class=Section2 style='layout-grid:15.6pt'>
<p class=MsoNormal><span lang=EN-US><![if !supportEmptyParas]> <![endif]><o:p></o:p></span></p>
</div>
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