How To Check Com1 Port In Windows 7

When you lot connect a new COM device or a USB device to your estimator (USB modem, mobile phone, Bluetooth adapter, serial to USB converters, etc.), Windows detects it using Plug-n-Play and assigns it a COM port number in the range of i to 255 (COM1, COM2, COM3, etc.). If this device is connected once more, the reserved COM (Advice, or Serial) port number is assigned to it. A new device gets the first free COM port number. Information technology often happens that when connected, external devices create several COM ports at in one case. In my example after connecting a Bluetooth adapter 10!!! new COM ports have appeared in the system.

A number of legacy applications are able to address only ii-digit COM port numbers, and won't piece of work with COM100 and higher. In the worst cases, these programs work only with COM1-COM9 ports. What if a device has got a higher COM port number? Is it possible to reset the numbering for reserved COM ports and delete assigned ports?

Contents:

How to Change a COM Port Number for a Device in Windows?
Find Out Which Procedure is Using a Serial COM Port in Windows
Resetting COM Port Numbers in Windows Registry

How to Modify a COM Port Number for a Device in Windows?

In Windows, you can manually change the COM port number assigned to a device. Suppose the necessary COM port is already busy, and you lot want to try to free it.

Open the Device Manager by running the devmgmt.msc command;
Select View->Show Hidden Devices in the carte du jour;
Then aggrandize Ports (COM & LPT) and find your device in the list;
Go to the Port Settings tab and click the Avant-garde button;
The electric current COM port number assigned to the device can exist found in the COM Port Number field;
To change it, open the drib-down list and select the COM port number you lot want to set.

Only more than often you cannot change the assigned COM port number to another one in the hardware properties, since all the "lower" COM ports are already in use.In this case, y'all demand to attempt to remove the COM port reservation

Expand the Ports (COM & LPT) branch, find which COM port number you need is assigned to (a pale icon means that this COM port is assigned, but this device is not currently connected);
Right-click it and select Uninstall ;
Now yous tin can assign the freed COM port to some other device. Once again open the properties of your device, go to the Port Settings -> Avant-garde tab. So go to the Port Settings tab and click Advanced. Select the free COM port in the dropdown list.

Notwithstanding, this method does non allow y'all to free the busy COM port in all cases.

Yous can get the full list of busy COM ports on Windows using PowerShell:

Get-WMIObject Win32_SerialPort | Select-Object Proper noun,DeviceID,Description
You can get the COM port number for a specific device by its name, for example:

Get-WMIObject Win32_SerialPort | Where-Object { $_.Proper noun -like "*Arduino*"}|select proper noun, deviceid
or
Get-WMIObject Win32_SerialPort | Where-Object { $_.Proper name -similar "*GPS*"}|select proper name, deviceid

Find Out Which Process is Using a Serial COM Port in Windows

You won't be able to release the COM port of a device that is used past Windows or a running program (procedure). Showtime, you lot demand to terminate the process that is currently using the COM port. You can apply the Process Explorer tool (by Sysinternals) to find out the name of the procedure using a particular COM port number (https://docs.microsoft.com/en-gb/sysinternals/downloads/process-explorer).

Starting time, you need to display the name of the service that uses the COM port. Run the PowerShell command:

get-pnpdevice -class Ports -ea 0| Select Proper noun, PNPDeviceID, Condition, Service

powershell - get com port service name

The service proper name of the specific COM port is shown in the Service cavalcade. For example, for COM2 it is Serial. Now you need to run Process Explorer every bit an administrator and select Find -> Find Handle or DLL from the menu. In the Handle or DLL substring line, enter the Service value obtained earlier. In our example, this is Serial .

Process Explorer should show the process proper name that is currently using your COM port. To release the COM port, kill the process or programme.

process explorer - getting process name is using serial com port number

Resetting COM Port Numbers in Windows Registry

Information about the COM ports in utilise is stored in CommDB registry parameter under the HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\COM Proper noun Arbiter reg key.

Open the Registry Editor (regedit.exe) and go to the registry key mentioned in a higher place;
Important! Nosotros strongly recommend you to backup this registry key (File -> Consign) earlier doing annihilation. If something goes wrong, yous can restore the original COM port configuration.
The value of ComDB parameter in the binary format determines the list of COM ports reserved in Windows. Each bit determines the state of the corresponding port (from 1 to 255). For instance, if you need to leave the reservation just for COM3, the hex value of ComDB volition be equal to 04 (0000 0100);
Important! Exist very attentive, and don't add any additional $.25 to the parameter, or the organisation will offset to fail into a BSOD.
If you lot have to reset all COM port bindings, change the value of ComDB to 0;
Notation. You tin can run across the complete list of COM ports connected in Windows under the registry key HKEY_LOCAL_MACHINE\HARDWARE\DEVICEMAP\SERIALCOMM. The registry entries nether the SERIALCOMM can but exist present only when underlying devices are continued and set up. This subkey is part of the HARDWARE key, and it is recreated each time the arrangement starts.
The HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Ports registry key contains the list of all assigned COM port numbers. You can remove all unnecessary port reservations. In our instance, we'll get out only COM3 and delete the residue ports;
Unplug all external devices and restart your computer;
After the reboot, connect the devices in the necessary social club, reinstall USB-to-serial converters, etc. All detected COM port devices volition be automatically detected by the system and assigned sequential COM port numbers.

Y'all can also use the following free tools to clean up reserved COM ports:

COM Name Czar Tool – this tool can help you to reset COM port reservations and notice the used COM port numbers. Download the tool and run it as an ambassador. Select the COM ports you want to release and click Clear unused Reservations and Remove non-present devices;
Device Cleanup Tool – the utility is used to search the registry for previously connected devices (nether the registry key HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Enum), remove unused devices, and clear COM port reservations.