diff --git a/targets/CMSIS-OS/ChibiOS/nanoCLR/Windows.Devices.Gpio/win_dev_gpio_native_Windows_Devices_Gpio_GpioPin.cpp b/targets/CMSIS-OS/ChibiOS/nanoCLR/Windows.Devices.Gpio/win_dev_gpio_native_Windows_Devices_Gpio_GpioPin.cpp
index c54aec619e..48a210bc14 100644
--- a/targets/CMSIS-OS/ChibiOS/nanoCLR/Windows.Devices.Gpio/win_dev_gpio_native_Windows_Devices_Gpio_GpioPin.cpp
+++ b/targets/CMSIS-OS/ChibiOS/nanoCLR/Windows.Devices.Gpio/win_dev_gpio_native_Windows_Devices_Gpio_GpioPin.cpp
@@ -89,8 +89,15 @@ static void debounceTimer_Callback( void* arg )
     if(lastPadValue == currentValue)
     {
         // value hasn't change for debounce interval so this is a valid change
-        // post a managed event with the current pin value
-        PostManagedEvent( EVENT_GPIO, 0, pinNumber, currentValue );
+
+        // flag to determine if there are any callbacks registered in managed code
+        bool callbacksRegistered = (pThis[ Library_win_dev_gpio_native_Windows_Devices_Gpio_GpioPin::FIELD___callbacks ].Dereference() != NULL);
+
+        // post a managed event with the current pin value, only if there is anyone listening otherwise don't bother
+        if(callbacksRegistered)
+        {
+            PostManagedEvent( EVENT_GPIO, 0, pinNumber, currentValue );
+        }
     }
 }
 
@@ -156,8 +163,14 @@ static void GpioEventCallback(void *arg)
         // read pad
         pThis[ Library_win_dev_gpio_native_Windows_Devices_Gpio_GpioPin::FIELD___lastInputValue ].NumericByRef().s4 = palReadLine(ioLine);
 
-        // post a managed event with the current pin reading
-        PostManagedEvent( EVENT_GPIO, 0, pinNumber, palReadLine(ioLine) );
+        // flag to determine if there are any callbacks registered in managed code
+        bool callbacksRegistered = (pThis[ Library_win_dev_gpio_native_Windows_Devices_Gpio_GpioPin::FIELD___callbacks ].Dereference() != NULL);
+
+        // post a managed event with the current pin reading, only if there is anyone listening otherwise don't bother
+        if(callbacksRegistered)
+        {
+            PostManagedEvent( EVENT_GPIO, 0, pinNumber, palReadLine(ioLine) );
+        }
     }
 
     chSysUnlockFromISR();
diff --git a/targets/CMSIS-OS/ChibiOS/nanoCLR/Windows.Devices.SerialCommunication/win_dev_serial_native_Windows_Devices_SerialCommunication_SerialDevice.cpp b/targets/CMSIS-OS/ChibiOS/nanoCLR/Windows.Devices.SerialCommunication/win_dev_serial_native_Windows_Devices_SerialCommunication_SerialDevice.cpp
index 432a751f0a..1e6579a591 100644
--- a/targets/CMSIS-OS/ChibiOS/nanoCLR/Windows.Devices.SerialCommunication/win_dev_serial_native_Windows_Devices_SerialCommunication_SerialDevice.cpp
+++ b/targets/CMSIS-OS/ChibiOS/nanoCLR/Windows.Devices.SerialCommunication/win_dev_serial_native_Windows_Devices_SerialCommunication_SerialDevice.cpp
@@ -256,7 +256,11 @@ static void RxChar(UARTDriver *uartp, uint16_t c)
     else
     {
         // no read operation ongoing, so fire an event
+       
         // post a managed event with the port index and event code (check if this is the watch char or just another another)
+        // TODO: check if callbacks are registered so this is called only if there is anyone listening otherwise don't bother
+        // for that to happen ChibiOS callback has to accept arg which we would passing the GpioPin CLR_RT_HeapBlock (see Gpio handler)
+        // check http://www.chibios.com/forum/viewtopic.php?f=36&t=4798
         PostManagedEvent( EVENT_SERIAL, 0, portIndex, (c == palUart->WatchChar) ? SerialData_WatchChar : SerialData_Chars );
     }