The PC interface and connection to your Transmitter

The MicroStar Encoder can communicate with your computer using a serial interface or a built in USB interface offered on revision 5.0 and later of the Encoder design. This article discusses how you establish the connection between the computer and the Encoder.

You will need to download and install the MicroStar PC application from my web site, You will find the install file in the download section of my web site. At this time support is only provided for Windows based personal computers. If you already have the MicroStar application installed and would like to update to a newer version first uninstall the current version using windows->control panel->add remove programs option.

You have three options to connect your PC to the Encoder:

1.) Using a serial or com port. In revision 5.0 you have the option of installing a USB interface and even if the interface is installed you have jumper options to enable its use.

2.) Using a USB interface. This is possible on revision 5.0 or later of the Encoder and when the USB option is installed, or by use of the upgrade described below.

3.) Older revision of the Encoder can be upgraded to USB using Jon Crick’s USB upgrade, the details are on my web site.

The following section describes the Com port and USB interface connections in a bit more detail:

Com port

Com ports were common in virtually all PCs for many years. Today it is rare to find a Com port in a PC. Com ports are also referred to as serial ports or RS232 ports. If your PC does not have a Com port you can buy USB to Com port adapters. These are available through online suppliers like Amazon and Ebay. These adapters were available through electronics chains like Best Buy and Radio Shack but they are getting harder to find.

If you buy a USB to Com port adapter follow the manufactures instructions on installing the drivers and testing the device.

You will need to know the Com port number for the port you intend to connect to the Encoder. This Com port number is available through the device manager on your PC. Please record the port number for later use in setting up the PC application.


If you use the revision 5.0 or later Encoder or the USB upgrade you will need to install drivers for the USB interface. The MicroStar uses the FTDI USB FT232RL chip. You can learn more about this chip at The drivers are also available on there web site as well as detailed instillation guides. I have also included the drivers on my web site. Please download and install the drivers as per FTDI’s instructions.

Drivers at:

Installation guides at:

This interface “looks” to your PC and to the Encoder like a Com or serial interface. After the drivers are installed you will need to determine the Com port number as described in the Com section above.

A note about Com port numbers

It has been my experience with USB to Com port adapters that if you plug them into a different physical USB ports on your PC they will setup with a different Com port number. This is something you need to be aware of because this will cause the PC application’s Com port number to need updating.

Establishing the physical connection

With the USB option physical connection is easy, you just plug the USB cable into your PC and the other end into your Encoder, the connection point will be someplace on your transmitter based on how you built your system.

If you are using a Com port you will need to locate the 9 pin D connector on your PC or on the USB to Com port adapter. This 9 pin D connector needs to plug into your transmitter. Please refer to my schematics available on my web site for details on how I designed the cabling. In my original design I wired the Encoder to a DIN plug that is mounted on the transmitter and then make a DIN to 9 pin D interface cable. Your connections may be different depending on how you built your system. Ultimately the signal connections that need to be established for the communications to work are defined below:

J7 on the Encoder DB9 on the PC

1 2

2 3

6 5

Establishing the communication link

Now you are ready to make the PC application “talk” to your Encoder. Please follow these steps to establish and test the communications link:

1.) Start the MicroStar application on your PC.

2.) Select the File->Option menu selection and you will see at Options dialog box appear. Enter the Com port you are using into this dialog box and select OK. The dialog box will disappear and the Com port will be saved.

3.) Make the physical connection between the PC and the Encoder.

4.) Apply power to your Encoder.

5.) Place the Run/Cal switch on your transmitter in the Cal mode.

6.) Using the PC application select Link->Read current aircraft. After a very short delay you should see a popup box indicating the data was received.


This procedure will establish and test the connections. Here are a few things that could go wrong and what you can do to fix the problems:

1.) If you see a message indicating the port cannot be opened you may have defined the wrong port or the port could be in use by another application.

2.) If you see an error receiving the buffer then you likely have a physical connection error of some kind and you need to check the cabling.