How to diagnose virtual Com ports

Virtual Com ports on Windows sometimes behave strangely. Often it might be due to Windows having installed two or more ports in ‘overlapped’ mode.

We have created a small utility program which can help troubleshoot the Com ports. Start with download it from here:


Then follow these instructions:

  1. Unzip the exe file to a directory of your choice.
  2. Open a command window as Administrator.
  3. Go to the directory you unzipped the exe file to.
  4. Type: MicrobitDeviceManager
  5. Answer ‘y’ on the first question confirming you are running the program as Administrator.
  6. Then just hit Enter on the following questions.
You will end up with a text file opened in Notepad with information about installed Com port etc that might help understanding what is causing problems. Note that the log text is appended to the file, so if the file already exists then the latest output will be at the end of the file.
The file might look like this example:

Mon Jan 11 08:40:24 2016:
Starting MicrobitDeviceManager v1.4
—– Installed devices info —–
       Ports Printer Port (LPT1)   ACPI\PNP0400\4&1E31B6B3&0
       Ports Communications Port (COM1)   ACPI\PNP0501\1
       Ports USB Serial Port (COM15)   FTDIBUS\VID_0403+PID_6001+A4004UIKA\0000
       Ports USB Serial Port (COM6)   FTDIBUS\VID_0403+PID_6001+FTDXR9QIA\0000
       Ports USB Serial Port (COM5)   FTDIBUS\VID_0403+PID_6001+FTE0SYMHA\0000
       HIDClass ———-   HID\VID_04D8&PID_0032\8&311935E5&0&0000
MB  HIDClass RRC 1258   HID\VID_1E3B&PID_1258&MI_00\9&7CD3CA5&0&0000
       Ports PCI Serial Port (COM3)   MF\PCI#VEN_9710&DEV_9835&SUBSYS_00121000&REV_01\6&2094081E&0&0000E2#CHILD0000
       Ports PCI Serial Port (COM2)   MF\PCI#VEN_9710&DEV_9835&SUBSYS_00121000&REV_01\6&2094081E&0&0000E2#CHILD0001
       Ports PCI Parallel Port (LPT2)   MF\PCI#VEN_9710&DEV_9835&SUBSYS_00121000&REV_01\6&2094081E&0&0000E2#CHILD0002
       HIDClass ———-   USB\VID_046D&PID_C508\5&27006488&0&10
       HIDClass ———-   USB\VID_046D&PID_C508\5&27006488&0&11
       HIDClass ———-   USB\VID_046D&PID_C508\5&27006488&0&12
       HIDClass ———-   USB\VID_04D8&PID_0032\7&1EB18643&0&3
MB  HIDClass RRC 1258   USB\VID_1E3B&PID_1258&MI_00\8&110C8D48&2&0000
MB  Ports RRC1258 COM2 (COM7)   USB\VID_1E3B&PID_1258&MI_01\8&110C8D48&2&0001
MB  Ports RRC1258 COM0 (COM9)   USB\VID_1E3B&PID_1258&MI_03\8&110C8D48&2&0003
MB  Ports RRC1258 COM1 (COM4)   USB\VID_1E3B&PID_1258&MI_05\8&110C8D48&2&0005
MB  Ports RRC1258 COMExtra (COM8)   USB\VID_1E3B&PID_1258&MI_07\8&110C8D48&2&0007
       Ports USB Serial Device (COM16)   USB\VID_1FC9&PID_2047\7&1EB18643&0&3
       Ports USB Serial Device (COM13)   USB\VID_1FC9&PID_2047\7&20C1FE&0&2
       Ports USB Serial Device (COM14)   USB\VID_1FC9&PID_2047\7&20C1FE&0&3
MB  Ports Microbit Virtual COM port (COM17)   FABULATECH\VSP\DEVICE03
—– Com port database Info —–
Maximum ports available: 256
Ports in use:
—– Com port matching —–
Number Inst. Com Db Action
1             X       X          None
2             X       X          None
3             X       X          None
4             X       X          None
5             X       X          None
6             X       X          None
7             X       X          None
8             X       X          None
9             X       X          None
13           X       X          None
14           X       X          None
15           X       X          None
16           X                   None
17           X       X         None 

Section —– Installed devices info —–:
Ports/devices marked with MB are installed by us. Make sure that all (COMx) ports listed have unique numbers. If not then there is ‘overlapping’ which can cause problems. The recommended fix is to uninstall/renumber overlapping ports.
Section —– Com port database Info —–:
The listed ports are those in use according to Windows Com port data base. It’s not unusual that there are more ports installed than listed in the Com port data base, which might cause problems when for ex. new Com ports are added to the system.
Section —– Com port matching —–:
This section shows if the Com port data base matches actually installed Com ports. It also shows if any action were taken regarding the Com port. If everything is ok then there should be an X on both the ‘Inst.’ and ‘Com Db’ columns. In the example above COM16 is present in the system but not marked as installed in the Com port data base, which could cause problems with ‘overlapping’ if more ports are added.

The program can also be used to:
  • Uninstall all Microbit ports/devices. Answer ‘U’ on the question ‘Do you want to uninstall all Microbit devices automatically?’ followed by ‘C’ to do that. It is advised to unplug all Microbit devices before uninstalling all Microbit devices.
  • Fix mismatches in the Com port data base. Answer ‘F’ on the question ‘Do you want to fix the Com port database?’ followed by ”C’ to do that. Ports that are installed in the system without being marked as in use in the Com port data base will be marked in use, and vice versa.
  • Interactively uninstall devices. This option should be used with more care in order to avoid accidental uninstallation of devices since it allows to uninstall not only Microbit devices. To use this option answer ‘I’ on the question ‘Do you want to interactively uninstall devices?’ followed by ‘C’ and then confirm the uninstallation device for device by the given instructions.

 Note that you are using this utility on your own responsibility. We only provide it as a support tool for computers having Com ports that are not installed correctly.


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