Academic Company Events NI Developer Zone Support Solutions Products & Services Contact NI MyNI
4 ratings:
 2.25 out of 5     Rate this Document

Why Do I Have Extra COM Ports in Measurement & Automation Explorer (MAX)?

Primary Software: Utility Software>>Measurement & Automation Explorer
Primary Software Version: 3.1
Primary Software Fixed Version: N/A
Secondary Software: N/A

Problem:
My PC has one serial and one parallel port. When I open Measurement & Automation Explorer and go to Devices and Interfaces -> Ports, I have a COM1, LPT1, and a COM3. I do not think there should be a COM3 on my computer, can I get rid of it?

Solution:
  1. First lets check if Windows is recognizing the extra COM (3) port. To do this, open the Device Manager. In Windows XP,

    1. Click the Start button on your desktop

    2. Select Control Panel

    3. Double click the System icon

    4. Select the Hardware tab

    5. Click the Device Manager button

    6. Now, expand Ports (COM & LPT)


    If only one COM port and one LPT port is shown, proceed to the step 2.

    If you see two COM ports, Windows is detecting a second COM port. Right click on the "extra" COM port and select Properties. In the location section, Windows will display the location of this COM Port.

    If you still think you have an extra COM port, you can try deleting it, however after you reboot, Window will probably auto detect the COM port and then reinstall the drivers for it. To see if this has happened, repeat step 1 after you reboot. If Windows has reinstalled this COM port, the hardware is most likely on your PC. To stop Windows from detecting this hardware, proceed to step 3.


  2. If the extra COM port is not listed in the Device Manager, it is possible that this COM port was installed at one time and has been removed, but the entry is still in the system registry. MAX pulls the COM devices from the system registry. You can try deleting COM 3 from the registry. To access the system registry,

    1. Click Start

    2. Select Run

    3. Type regedit

    4. Click OK


    In Windows XP, the COM ports will be listed in HKEY_LOCAL_MACHINE -> HARDWARE -> DEVICEMAP -> SERIALCOMM. Try deleting COM 3 and then reboot your computer. Now, go back to the registry entry you deleted and check to see if it is still there. If it is, Windows is detecting this device and most likely it is on your computer. To stop Windows from detecting this hardware, proceed to step 3.


  3. To stop Windows from detecting your "extra" COM device, you may disable it in the system BIOS. Unfortunately there are many versions of the system BIOS and all are quite different. Therefore, step by step instructions cannot be given. In general you may access the system bios by pressing Delete, F2 or F12 when your machine is powered on. Often there is a message at bootup stating "Press Del key to enter setup." Once in the BIOS you may find that your motherboard is equipped with a device that is showing up as a COM device. For example, an infrared port. When you disable this device, Windows will no longer detect it.


    4. Related Links:

    Attachments:





    Report Date: 02/02/2005
    Last Updated: 02/04/2005
    Document ID: 3I1GJMVB

    Your Feedback! poor Poor  |  Excellent excellent   Yes No
     Document Quality? 
     Answered Your Question? 
      1 2 3 4 5
    Please Contact NI for all product and support inquiries.submit