diff --git a/FlippR-Driver/src/utility/GPIOInterface.h b/FlippR-Driver/src/utility/GPIOInterface.h
index bc029bb..6dbf77c 100644
--- a/FlippR-Driver/src/utility/GPIOInterface.h
+++ b/FlippR-Driver/src/utility/GPIOInterface.h
@@ -23,10 +23,7 @@ namespace utility
 class GPIOInterface
 {
 public:
-  GPIOInterface();
-
-  virtual ~GPIOInterface()
-  {};
+  virtual ~GPIOInterface() {};
 /* todo ???? */
   static void initialize_input_pin(char address);
 
diff --git a/FlippR-Driver/src/utility/OutputGPIOInterface.h b/FlippR-Driver/src/utility/OutputGPIOInterface.h
index adfc2cb..1896509 100644
--- a/FlippR-Driver/src/utility/OutputGPIOInterface.h
+++ b/FlippR-Driver/src/utility/OutputGPIOInterface.h
@@ -19,10 +19,13 @@ namespace flippR_driver
 {
 namespace utility
 {
+
 class OutputGPIOInterface : public GPIOInterface
 {
 
 public:
+  virtual ~OutputGPIOInterface() = default;
+
   void activate_output_item(output::items::OutputItem *item);
   void deactivate_output_item(output::items::OutputItem *item);
 
@@ -32,6 +35,7 @@ private:
   std::mutex output_item_mutex;
 
 };
+
 }
 }
 
diff --git a/FlippR-Driver/src/utility/OutputGpioInterface.cpp b/FlippR-Driver/src/utility/OutputGpioInterface.cpp
new file mode 100644
index 0000000..ba05588
--- /dev/null
+++ b/FlippR-Driver/src/utility/OutputGpioInterface.cpp
@@ -0,0 +1,28 @@
+//
+// Created by rhetenor on 21.11.18.
+//
+
+namespace flippR_driver
+{
+namespace utility
+{
+
+  void OutputGPIOInterface::activate_output_item(output::items::OutputItem *item)
+  {
+    std::lock_guard<std::mutex> guard(output_item_mutex);
+
+  }
+
+  void OutputGPIOInterface::deactivate_output_item(output::items::OutputItem *item)
+  {
+    std::lock_guard<std::mutex> guard(output_item_mutex);
+
+  }
+
+  void OutputGPIOInterface::write_display(Display &display)
+  {
+
+  }
+
+}
+}