RB Series Support

Determining or Changing the USB Driver’s COM Port Setting

Last Revision: November 26, 2003

The information in this document applies to:

  • Users of any Cedrus USB-based product who want to know or change the USB driver’s COM port setting.



For maximum compatibility with application programs, the Cedrus-supplied USB (Universal Serial Bus) drivers setup a fake serial port, e.g. COM4 or COM5. Therefore, application programs that used to support the serial port can continue to do so with no modifications. This document shows you how to find out what your device’s COM port is and how to change it.


Method 1 – Using HyperTerminal (Easiest)

The Windows operating system ships with a program called HyperTerminal. You can use it to determine (but not change) which COM ports you have, including the one that was setup by the USB drivers:

  • Click on: the Start button, then Programs (or All Programs if using Windows XP), then Accessories, then Communications, then click on HyperTerminal.

  • HyperTerminal’s main window will appear with a small dialog (screen) on top of it entitled “Connection Description”. Click on Cancel. You should now be seeing HyperTerminal’s main window.

  • Click on the File menu and then on Properties. A new dialog will appear.

In the bottom half of the Properties dialog, these a option called “Connect Using:” with a menu. Click on it. This menu will show you all the COM ports currently available on your computer. Usually, the USB drivers will setup up its port starting at COM4 or higher.

After determining the COM port, you can click on Cancel to close the Properties dialog and exit HyperTerminal.


Method 2 – Using the Device Manager

Using the Device Manager, you can both view and change the COM port setting. The following instructions were written for Windows XP; they might vary slightly on other versions of Windows.

  • Click on the Start button and then on Control Panel. A window will open showing you all the available control panels.

  • Double-click on the System control panel. A dialog (screen) entitled System Properties will appear.

  • The System Properties has several tabs. Click on the Hardware tab.

  • Click on the Device Manager button. A new window opens showing a list of all the available devices on your computer such as keyboard, disk drives, and so forth.

  • Double-click on Ports (COM & LPT). A list of all available serial and parallel port devices will appear. The window might look something like this:

  • Your Cedrus USB product should appear in the list serial USB devices, e.g. “Cedrus RB-x30 Response Pad” along with the COM port number that was assigned to it.

If you would like to change the COM port number that’s been assigned to your Cedrus USB product:

  • Disconnect your Cedrus USB product from the computer.

  • With the mouse, right-click on the product name with the mouse. A menu will appear.

  • On the menu, click on Properties. A dialog (window) appears.

  • Click on the Port Settings tab.

  • Click on the Advanced button. A second dialog appears.

  • On this new dialog, there is “COM Port Number” option near the top. Change it to suit your needs and click on OK to close the dialog. You might get a warning message about other programs using the device and whether you wish to continue. Click on Yes.

  • Click on OK again to close the first dialog.

  • Close the Device Manager. Note that the Device Manager might still show the old COM port number. If you close it and re-open it, you will then be able to see the new COM port number listed.

  • You can now reconnect your product to the computer.