diff --git a/commandwidget.cpp b/commandwidget.cpp
--- a/commandwidget.cpp
+++ b/commandwidget.cpp
@@ -77,6 +77,16 @@ void CommandWidget::onSendClicked()
 void CommandWidget::onASCIIToggled(bool checked)
 {
     ui->leCommand->setMode(checked);
+    if (checked)
+    {
+        storedHexText = ui->leCommand->text();
+        ui->leCommand->setText(storedAsciiText);
+    }
+    else
+    {
+        storedAsciiText = ui->leCommand->text();
+        ui->leCommand->setText(storedHexText);
+    }
 }
 
 bool CommandWidget::isASCIIMode()
diff --git a/commandwidget.h b/commandwidget.h
--- a/commandwidget.h
+++ b/commandwidget.h
@@ -46,6 +46,9 @@ signals:
 
 private:
     Ui::CommandWidget *ui;
+    QString storedAsciiText;
+    QString storedHexText;
+
     bool isASCIIMode(); // true: ascii mode, false hex mode
 
 private slots: