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<td >Qt 5.9</td><td ><a href="qtserialport-index.html">Qt Serial Port</a></td><td ><a href="qtserialport-examples.html">Qt Serial Port Examples</a></td><td >Terminal Example</td></tr></table><table class="buildversion"><tr>
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<h3><a name="toc">Contents</a></h3>
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<li class="level1"><a href="#running-the-example">Running the Example</a></li>
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<h1 class="title">Terminal Example</h1>
<span class="subtitle"></span>
<!-- $$$terminal-description -->
<div class="descr"> <a name="details"></a>
<p><i>Terminal</i> shows how to create a terminal for a simple serial interface by using <a href="qtserialport-index.html">Qt Serial Port</a>.</p>
<p class="centerAlign"><img src="images/terminal-example.png" alt="" /></p><p>This example shows the main features of the <a href="qserialport.html">QSerialPort</a> class, like configuration, I/O implementation and so forth. Also, the class <a href="qserialportinfo.html">QSerialPortInfo</a> is invoked to display information about the serial ports available in the system.</p>
<p><a href="qserialport.html">QSerialPort</a> supports two general programming approaches:</p>
<ul>
<li><i>The asynchronous (non-blocking) approach.</i> Operations are scheduled and performed when the control returns to Qt's event loop. <a href="qserialport.html">QSerialPort</a> emits a signal when the operation is finished. For example, QSerialPort::write() returns immediately. When the data is sent to the serial port, <a href="qserialport.html">QSerialPort</a> emits bytesWritten().</li>
<li><i>The synchronous (blocking) approach.</i> In non-GUI and multithreaded applications, the <code>waitFor...()</code> functions can be called (i.e. <a href="qserialport.html#waitForReadyRead">QSerialPort::waitForReadyRead</a>()) to suspend the calling thread until the operation has completed.</li>
</ul>
<p>In this example, the asynchronous approach is demonstrated. The <a href="qtserialport-blockingslave-example.html">Blocking Slave</a> example illustrates the synchronous approach.</p>
<p>Our example contains some GUI widgets:</p>
<ul>
<li><a href="qtserialport-terminal-mainwindow-cpp.html">MainWindow</a> - is the main application window that contains all the working logic for the serial port programming, including configuration, I/O processing and so forth, while inheriting the QMainWindow.</li>
<li><a href="qtserialport-terminal-console-cpp.html">Console</a> - is the central widget of the main window, displaying the transmitted or received data. The widget is derived from the QPlainTextEdit class.</li>
<li><a href="qtserialport-terminal-settingsdialog-cpp.html">SettingsDialog</a> - is a dialog for configuring the serial port, as well as for displaying the available serial ports and information about them.</li>
</ul>
<p>The serial port is instantiated in the <a href="qtserialport-terminal-mainwindow-cpp.html">MainWindow</a> constructor. The main widget is passed as the parent, so the object deletion happens automatically according to the parent and child mechanism in Qt:</p>
<pre class="cpp">
MainWindow<span class="operator">::</span>MainWindow(<span class="type">QWidget</span> <span class="operator">*</span>parent) :
<span class="type">QMainWindow</span>(parent)<span class="operator">,</span>
ui(<span class="keyword">new</span> Ui<span class="operator">::</span>MainWindow)
{
...
serial <span class="operator">=</span> <span class="keyword">new</span> <span class="type"><a href="qserialport.html">QSerialPort</a></span>(<span class="keyword">this</span>);
</pre>
<p>The only <a href="qserialport.html">QSerialPort</a> signal invoked in this example is readyRead(), which shows that new data has been received and hence available:</p>
<pre class="qml">
...
connect(serial<span class="operator">,</span> <span class="operator">&</span><span class="type"><a href="qserialport.html">QSerialPort</a></span><span class="operator">::</span>readyRead<span class="operator">,</span> <span class="keyword">this</span><span class="operator">,</span> <span class="operator">&</span>MainWindow<span class="operator">::</span>readData);
...
}
</pre>
<p>Clicking on the <b>Connect</b> button invokes the <code>openSerialPort()</code> slot:</p>
<pre class="cpp">
<span class="type">void</span> MainWindow<span class="operator">::</span>openSerialPort()
{
SettingsDialog<span class="operator">::</span>Settings p <span class="operator">=</span> settings<span class="operator">-</span><span class="operator">></span>settings();
serial<span class="operator">-</span><span class="operator">></span>setPortName(p<span class="operator">.</span>name);
serial<span class="operator">-</span><span class="operator">></span>setBaudRate(p<span class="operator">.</span>baudRate);
serial<span class="operator">-</span><span class="operator">></span>setDataBits(p<span class="operator">.</span>dataBits);
serial<span class="operator">-</span><span class="operator">></span>setParity(p<span class="operator">.</span>parity);
serial<span class="operator">-</span><span class="operator">></span>setStopBits(p<span class="operator">.</span>stopBits);
serial<span class="operator">-</span><span class="operator">></span>setFlowControl(p<span class="operator">.</span>flowControl);
<span class="keyword">if</span> (serial<span class="operator">-</span><span class="operator">></span>open(<span class="type">QIODevice</span><span class="operator">::</span>ReadWrite)) {
console<span class="operator">-</span><span class="operator">></span>setEnabled(<span class="keyword">true</span>);
console<span class="operator">-</span><span class="operator">></span>setLocalEchoEnabled(p<span class="operator">.</span>localEchoEnabled);
ui<span class="operator">-</span><span class="operator">></span>actionConnect<span class="operator">-</span><span class="operator">></span>setEnabled(<span class="keyword">false</span>);
ui<span class="operator">-</span><span class="operator">></span>actionDisconnect<span class="operator">-</span><span class="operator">></span>setEnabled(<span class="keyword">true</span>);
ui<span class="operator">-</span><span class="operator">></span>actionConfigure<span class="operator">-</span><span class="operator">></span>setEnabled(<span class="keyword">false</span>);
showStatusMessage(tr(<span class="string">"Connected to %1 : %2, %3, %4, %5, %6"</span>)
<span class="operator">.</span>arg(p<span class="operator">.</span>name)<span class="operator">.</span>arg(p<span class="operator">.</span>stringBaudRate)<span class="operator">.</span>arg(p<span class="operator">.</span>stringDataBits)
<span class="operator">.</span>arg(p<span class="operator">.</span>stringParity)<span class="operator">.</span>arg(p<span class="operator">.</span>stringStopBits)<span class="operator">.</span>arg(p<span class="operator">.</span>stringFlowControl));
} <span class="keyword">else</span> {
<span class="type">QMessageBox</span><span class="operator">::</span>critical(<span class="keyword">this</span><span class="operator">,</span> tr(<span class="string">"Error"</span>)<span class="operator">,</span> serial<span class="operator">-</span><span class="operator">></span>errorString());
showStatusMessage(tr(<span class="string">"Open error"</span>));
}
}
</pre>
<p>In this slot, the settings are read from <a href="qtserialport-terminal-settingsdialog-cpp.html">SettingsDialog</a> and an attempt is made to open and initialize the serial port accordingly. If successful, the status bar displays a message that the opening was successful with the given configuration; otherwise, a messagebox is displayed with the appropriate error code and message. If the serial port settings have never been called <a href="qtserialport-terminal-settingsdialog-cpp.html">SettingsDialog</a>, then the terminal attempts to open the port with the default settings: 9600 8N1.</p>
<p>Clicking on the <b>Disconnect</b> button invokes the <code>closeSerialPort()</code> slot:</p>
<pre class="cpp">
<span class="type">void</span> MainWindow<span class="operator">::</span>closeSerialPort()
{
<span class="keyword">if</span> (serial<span class="operator">-</span><span class="operator">></span>isOpen())
serial<span class="operator">-</span><span class="operator">></span>close();
console<span class="operator">-</span><span class="operator">></span>setEnabled(<span class="keyword">false</span>);
ui<span class="operator">-</span><span class="operator">></span>actionConnect<span class="operator">-</span><span class="operator">></span>setEnabled(<span class="keyword">true</span>);
ui<span class="operator">-</span><span class="operator">></span>actionDisconnect<span class="operator">-</span><span class="operator">></span>setEnabled(<span class="keyword">false</span>);
ui<span class="operator">-</span><span class="operator">></span>actionConfigure<span class="operator">-</span><span class="operator">></span>setEnabled(<span class="keyword">true</span>);
showStatusMessage(tr(<span class="string">"Disconnected"</span>));
}
</pre>
<p>In this case, handled by the closure of the serial port.</p>
<p>Typing characters in the console invokes the <code>writeData()</code> slot:</p>
<pre class="cpp">
<span class="type">void</span> MainWindow<span class="operator">::</span>writeData(<span class="keyword">const</span> <span class="type">QByteArray</span> <span class="operator">&</span>data)
{
serial<span class="operator">-</span><span class="operator">></span>write(data);
}
</pre>
<p>This slot sends the characters typed in the given <a href="qtserialport-terminal-console-cpp.html">Console</a> widget to the serial port.</p>
<p>When the serial port receives new data, the signal readyRead() is emitted, and that signal is connected to the <code>MainWindow::readData()</code> slot:</p>
<pre class="cpp">
<span class="type">void</span> MainWindow<span class="operator">::</span>readData()
{
<span class="type">QByteArray</span> data <span class="operator">=</span> serial<span class="operator">-</span><span class="operator">></span>readAll();
console<span class="operator">-</span><span class="operator">></span>putData(data);
}
</pre>
<p>This slot reads the data from the serial port and displays that in the <a href="qtserialport-terminal-console-cpp.html">Console</a> widget.</p>
<p>Clicking on the <b>Configure</b> button invokes the <code>show()</code> slot which belongs to the <a href="qtserialport-terminal-settingsdialog-cpp.html">SettingsDialog</a> widget.</p>
<p>This method displays the <a href="qtserialport-terminal-settingsdialog-cpp.html">SettingsDialog</a> in which the user can choose the desired serial port, see the information about the selected port, and set the desired parameters of the given serial port.</p>
<a name="running-the-example"></a>
<h2 id="running-the-example">Running the Example</h2>
<p>To run the example from Qt Creator, open the <b>Welcome</b> mode and select the example from <b>Examples</b>. For more information, visit Building and Running an Example.</p>
<p>Files:</p>
<ul>
<li><a href="qtserialport-terminal-console-cpp.html">terminal/console.cpp</a></li>
<li><a href="qtserialport-terminal-console-h.html">terminal/console.h</a></li>
<li><a href="qtserialport-terminal-mainwindow-cpp.html">terminal/mainwindow.cpp</a></li>
<li><a href="qtserialport-terminal-mainwindow-h.html">terminal/mainwindow.h</a></li>
<li><a href="qtserialport-terminal-mainwindow-ui.html">terminal/mainwindow.ui</a></li>
<li><a href="qtserialport-terminal-settingsdialog-cpp.html">terminal/settingsdialog.cpp</a></li>
<li><a href="qtserialport-terminal-settingsdialog-h.html">terminal/settingsdialog.h</a></li>
<li><a href="qtserialport-terminal-settingsdialog-ui.html">terminal/settingsdialog.ui</a></li>
<li><a href="qtserialport-terminal-main-cpp.html">terminal/main.cpp</a></li>
<li><a href="qtserialport-terminal-terminal-pro.html">terminal/terminal.pro</a></li>
<li><a href="qtserialport-terminal-terminal-qrc.html">terminal/terminal.qrc</a></li>
</ul>
<p>Images:</p>
<ul>
<li><a href="images/used-in-examples/terminal/images/application-exit.png">terminal/images/application-exit.png</a></li>
<li><a href="images/used-in-examples/terminal/images/clear.png">terminal/images/clear.png</a></li>
<li><a href="images/used-in-examples/terminal/images/connect.png">terminal/images/connect.png</a></li>
<li><a href="images/used-in-examples/terminal/images/disconnect.png">terminal/images/disconnect.png</a></li>
<li><a href="images/used-in-examples/terminal/images/settings.png">terminal/images/settings.png</a></li>
</ul>
</div>
<p><b>See also </b><a href="qtserialport-blockingslave-example.html">Blocking Slave Example</a>.</p>
<!-- @@@terminal -->
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