diff --git a/mainwindow.cpp b/mainwindow.cpp
--- a/mainwindow.cpp
+++ b/mainwindow.cpp
@@ -168,7 +168,7 @@ void MainWindow::onPortToggled(bool open
 
 void MainWindow::onDataReady()
 {
-    if (ui->actionStart->isChecked())
+    if (!ui->actionPause->isChecked())
     {
         QByteArray data = serialPort.readAll();
         addData((unsigned char)(data[0]));
diff --git a/mainwindow.ui b/mainwindow.ui
--- a/mainwindow.ui
+++ b/mainwindow.ui
@@ -407,7 +407,7 @@
      <x>0</x>
      <y>0</y>
      <width>653</width>
-     <height>23</height>
+     <height>20</height>
     </rect>
    </property>
    <widget class="QMenu" name="menuFile">
@@ -434,19 +434,22 @@
    <attribute name="toolBarBreak">
     <bool>false</bool>
    </attribute>
-   <addaction name="actionStart"/>
+   <addaction name="actionPause"/>
    <addaction name="actionClear"/>
   </widget>
   <widget class="QStatusBar" name="statusBar"/>
-  <action name="actionStart">
+  <action name="actionPause">
    <property name="checkable">
     <bool>true</bool>
    </property>
    <property name="checked">
-    <bool>true</bool>
+    <bool>false</bool>
    </property>
    <property name="text">
-    <string>Start</string>
+    <string>Pause</string>
+   </property>
+   <property name="toolTip">
+    <string>Pause Plotting</string>
    </property>
   </action>
   <action name="actionClear">