Connecting Arduino to Flight Simulator X

Introduction

Welcome to my tutorial on how to connect Arduino to Microsoft Flight simulator.
This is the easiest method I found.
FSX SDK exists but lacks of documentation, is not useful as it requires huge amount of code. I wanted something easy and after some research I was able to connect to FSX using the FSUIPC API. Please note that to get some of the functionality you have to register FSUIPC. And I thought sharing this with the world, maybe someone will benefit. In this ``tutorial`` I will explain the process and not just give you the code. I believe in understanding not just knowing.

 

System design

Amazing system design :)

Amazing!!!! :) You get the picture
The Arduino send serial data to a VB application that uses the FSUIPC API to control FSX. In this tutorial we are going to control the Landing gear.

Requirements:

1. Microsoft Flight Simulator X (FSX)
2. FSUIPC 4, you can download it from:
   • http://www.schiratti.com/dowson.html
     
3. FSUIPC SDK
   • You can also download it from the website shown above
   • Scroll a bit down :)
4. Arduino (any version)
   • And how to get the input from a simple switch
   • Switch, 1K resistor and some wires
5. Microsoft Visual Studio (I have 2010)
   • VB.NET
   • .net framework (any) I have 4

Before you start up make sure that you have everything installed

Arduino part

The first thing we have to do is to make the switch. Use my schematic and make your own simple switch circuit.

Note that the switch is a simple on/off switch just like this one here (I'm trying to make a panel for a homemade flight simulator)

We can proceed to the code for the Arduino.
Our Arduino scenario
We have to get the state of the switch; the Arduino is going to monitor the state of the switch with the digitalRead function.
When we get the state of our switch we will send serial data back to the computer.
Use your Arduino IDE and upload the code

Arduino Code

/* start of code */

int LandingGear = 3; /* Landing gear*/

void setup() {
  Serial.begin(9600);
  pinMode(LandingGear, INPUT);
 
}

void loop() {
  if (digitalRead(LandingGear) == HIGH){Serial.print("GEAR1");} else{Serial.print("GEAR0");}
 
  Serial.println();
  delay(1000);
}

/* End of code*/
What we need for the VB .NET solution?
DLL found in the FSUIPC SDK
You can find the dll in the ZIP file FSUIPCDotNetClient2.0.zip that came with the SDK
After you locate the DLL extract it in a folder of your option

Desktop application

Start a new project by going to file -> New Project
Select a Visual Basic .NET Windows Forms Application and give it a name of your choice
I gave the name StavrosFSX Arduino
Press the OK button to create the project
Just to be safe, SAVE your application
File -> SAVE ALL
Now it's a very important step we have to add a reference to the DLL that we found previously.
In the folder that Microsoft Visual studio created in my documents I am going to save the DLL so I don't have to worry about finding it later (if you are going to do the same make sure that you copy the xml file as well, (Note that the name of the folder is the same name of your project).

FSUIPC dll

You can also manipulate the references from the solution explorer but anyway.

Select the References Tab at your left and then the Add button, from the dialog that pops up click browse and find the DLL inside the folder you copied it.

The software is going to report the installed reference 

Press the Save all menu one more time and let's start programming :)
As we saw before the Arduino includes one switch and we can get reports from the Arduino through the serial port. We are going to use the serial port to collect value of the switch and we are going to use the API (DLL) to send it to FSX.
Simple :)

Design

I gave this names, please use your own style when naming the controllers don't use my bad naming I was in hurry :)

Serial Data observation

Now open your Arduino serial terminal and observe the different values that the Arduino transmits through the serial port, observe also the difference when we close and open the circuit. From here we make a mental note of the com port and the baud rate, in my case COM17 and baud rate 9600. Make sure the baud is the same with the Arduino in the void setup() or your data will be ``scrambled``

User settings

Now I like to have the program remember my com port and my baud rate so I don't have to type them all the time. Visual studio and the .NET framework allow us to do with the Application settings. You can set the user settings using the project properties as we did above when we referenced the API. Note that we can change the settings later in our code.

Get the user settings

Now let's write up a bit of code to get and save the settings.
Double click on your form in order to get the form load code. And create a new sub to handle the loading into the form.
Your code should look like this
Private
Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles
MyBase.Load
loadUserSettings()

End
Sub


 

Private
Sub loadUserSettings()

Try

txtComPort.Text = My.Settings.ComPort
txtBaudRate.Text = My.Settings.BaudRate

Catch ex As
Exception

MsgBox(ex.ToString)

End
Try


End
Sub
For simple operations we can always use the load method of our form but I prefer to split the code because I'm planning to extend the code later and easier to handle and understand.
Run your application and check that everything is ok

Save the user settings

Private
Sub btnSAVESETTINGS_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnSAVESETTINGS.Click

Try


If txtBaudRate.Text <> ""
And txtComPort.Text <> ""
Then


My.Settings.ComPort = txtComPort.Text

My.Settings.BaudRate = txtBaudRate.Text

My.Settings.Save()

Else

MsgBox("Please type your connection settings")

End
If


 

Catch ex As
Exception

MsgBox(ex.ToString)

End
Try


End
Sub
It's a simple operation and we will use the button sub to handle the process.

Main programming

How our program works?
Our program works by reading the serial port and when our program finds a difference in the readings it will transmit the appropriate command to the API. We are going to make our program to create a new thread for this purpose. The new thread will allow the user to have control of the form and allow him or her to stop the process.
Dim s1 As
SerialPort

Dim myThread As
Thread
Using this code we declare our serial port and the thread that we are going to use, put this code in the main class of your program.
Now let's double click our connect button and write the following code
Private
Sub bntConnect_to_serial_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles bntConnect_to_serial.Click

Try

s1 = New
SerialPort(My.Settings.ComPort, My.Settings.BaudRate)
s1.Open()
myThread = New
Thread(AddressOf read_serial_port)
myThread.Start()

Catch ex As
Exception

MsgBox(ex.ToString)

End
Try


End
Sub


 

Private
Sub read_serial_port()

'open the port, read the stream, send the stream to the thread


Try


While s1.IsOpen

Dim serialString As
String = s1.ReadLine
processReadings(serialString)

End
While


Catch ex As
Exception

MsgBox(ex.ToString)

End
Try


End
Sub


Delegate
Sub
CallBack(ByVal updateText As
String)

Dim messageFromSerial As
String


Private
Sub processReadings(ByVal readingText As
String)

If txtDATA_FROM_SERIAL.InvokeRequired Then


Dim d As
New
CallBack(AddressOf processReadings)

Me.Invoke(d, New
Object() {readingText})

Else

messageFromSerial = readingText
txtDATA_FROM_SERIAL.Text = messageFromSerial

If messageFromSerial = "GEAR1" & vbCr Then

picLandingGear.BackColor = Color.Green
lblLandGear.Text = "DOWN"


ElseIf messageFromSerial = "GEAR0" & vbCr Then

picLandingGear.BackColor = Color.Gray
lblLandGear.Text = "UP"


End
If


End
If


End
Sub
What this code does is to open the serial port and start a new thread
The thread will read the serial stream and send it for processing into the sub process processReadings() that takes as arguments the last reading. Because the new thread cannot interact directly with the main form we have to set a callback function, so as you noted the following code

If txtDATA_FROM_SERIAL.InvokeRequired Then


Dim d As
New
CallBack(AddressOf processReadings)

Me.Invoke(d, New
Object() {readingText})

 
We make sure that our thread can interact with the main form.
We then check if the Arduino sends the GEAR1 or GEAR0 that represent down and up.
Next thing to do is to talk about the API and how we will make it work.
We are going to use 2 documents found in the SDK the user guide as PDF and the FSUIPC4 Offsets Status PDF.
We are going to use our documents to learn how to write the API call.
In this tutorial we want to read and write a value to FSX. The guide specifies this as an offset.
To get the gear status we use
Dim gearstatus As
Offset(Of
Integer) = New FSUIPC.Offset(Of
Integer)(&HBE8)
And because the offset in the API guide is 0BE8 we replace the 0 with an H.
Now we have to set our program to read when it starts the value from FSX. We will use the form load to call a small procedure (sub)
Dim landingGear As
Integer

Private
Sub getGearStatus()

Try


FSUIPCConnection.Process()
landingGear = gearstatus.Value

Catch ex As
Exception

MsgBox(ex.ToString)

End
Try


End
Sub
You can see that I set a variable called landing Gear in the main class so our code can use it.
You can also see the exception handling try catch. If we start our application without FSX running we will get the following exception

Now for the useful part of our code :)
From the offset guide we can see that
Gear control: 0=Up, 16383=Down
So when offset gives 0 then the gear is up and 16383 is down.
Let's make a new sub process to handle the change and send it to the API

Private
Sub setLandingGear(ByVal p1 As
Integer)

If p1 <> landingGear Then

gearstatus.Value = p1

FSUIPCConnection.Process()

End
If


End
Sub
To use this code put the name of the sub with the number 0 or 16383 the sub will check if the system already has it set or else will set the new value.
Lastly we are going to create a control mechanism to close the serial port when we want.
Just replace this piece of code
Private
Sub bntConnect_to_serial_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles bntConnect_to_serial.Click

Try


If myThread.IsAlive Then

bntConnect_to_serial.Text = "Read Serial port"

myThread.Abort()

If s1.IsOpen Then

s1.Close()

End
If


End
If

s1 = New
SerialPort(My.Settings.ComPort, My.Settings.BaudRate)
s1.Open()
myThread = New
Thread(AddressOf read_serial_port)
myThread.Start()
bntConnect_to_serial.Text = "stop serial port"


Catch ex As
Exception

MsgBox(ex.ToString)

End
Try


End
Sub

Testing

You can get the full code by clicking here

Now let's test our application
Open FSX and load a simple flight making sure you are airborne, also make sure that your aircraft supports landing gear function :)
Get out of full screen and set the option in settings general pause on task switch so FSX will not pause when you click away.
After you connect your Arduino to your pc and you lunch the application you should have a fully functional system.
The landing gear should go up and down. If you have full realistic mode on FSX make sure you are 3000 feet and less altitude.
Hope it helps at some point; don't hesitate to contact me through the comments.

Tools

Visual basic .net 2010
Arduino - 1.0 IDE
FSUIPC 4 API
Microsoft Word