Send a keyboard event from labview to C#

Question

Hi,
We currently have a program in c# that takes keyboard inputs from a user and will fly a quadrotor. We aim to have a LabView .vi generate keyboard commands based on our experiment and send the commands to the c# code creating a feedback loop where the .vi will keep track of sensor and experimental data.
Our problem is that we have tried many different methods to send the keyboard commands in LabView. 
1) http://zone.ni.com/devzone/cda/epd/p/id/3711
2) http://forums.ni.com/t5/LabVIEW/Send-keyboard-commands-to-another-windows-program/td-p/330670/page/2
as well as other variations and similar .vi's that do the same thing. Here is an example of a .vi used to press the letter "t" once.
http://i.imgur.com/hwmjZ.png
All of them can write the string to a text (open notepad put cursor in blank window) file but none can do it in such a way that it is detected by the c# code. On my own I can open and run the c# code and press keyboard buttons myself and the commands are recognized, so I think it could be an issue with how LabView sends the keyboard events and how c# reads them. Here is the c# code segment that we are using to read the input commands:
public override List<String> GetPressedButtons()
          KeyboardState state = device.GetCurrentKeyboardState();
          List<String> buttonsPressed = new List<String>();
          foreach (Key key in Enum.GetValues(typeof(Key)))
                    if (state[key])
                              if (!buttonsPressed.Contains(key.ToString()))
                                        buttonsPressed.Add(key.ToString());
          return buttonsPressed;
Can anyone help trying to figure out why using the keybd_event function in LabView can not interface correctly with the above detection code in c#? I can provide any code and clarification if you think it can be helpful.
Thanks,
Andy

Answer 1

Hi,
I can't say with certainty where the problem is or even how many there are. I do know that the KeyboardListener.cs class should work according to what I have read online. I also know that if I press the keyboard myself then the state is changed and the correct action is taken. If I try to issue an event from Labview then the event is not captured. Here is the code, it is rather large ~20 MB.
https://www.dropbox.com/s/vsvcje1ro364otu/ARDrone.zip
https://www.dropbox.com/s/p3h3tj8bcqc29gk/Forward_backward0924.vi
The key listener is in ARDroneInput>Utils>KeyboardListener.cs and the polling takes place in ARDroneInput>KeyboardInput.cs
The reason I wanted to use keyboard inputs is because the quadrotor we are using takes keyboard commands W,A,S,D,T and L. Initially I thought having Labview issue these commands would be the simplest method. That may not be the case.
I was just thinking that it is not necessary that key events are sent from Labview. Instead, one could send an array representing the frequency of each button press rather than the button press directly. In that case an array that is updated continuously from Labview will just have to be kept track of in the C# code. The C# can then convert that to whatever control input we want. Can it be easier to send a vector of numbers in real time to C#?
If you think it is better to establish a connection between Labview and C# using .NET to send keyboard commands (rather than the vector idea above) can you explain that a little more? How does one go about doing that? If you think the vector idea is simpler how should the interface be set-up?
I just talked with my collegue and we think that maintaing a .txt file in Labview and having C# read it is the best option. We will begin working on that and will update you tomorrow.
Thanks,
Andy