Problems under Windows 11 with normal Serial Port acess and with USB to Serial Access

Copper Contributor



I encounter some problems under Windows 11 23H2 to access a simple Serial Port under .NET in C#.

My earlier installations with Windows 10 and earlier worked fine with that code and since I try on my new Notebook Dell XPS 9720 which only proposes USB3-C ports I added a USB3-C to USB3.1 Switch on which I added different USB to RS232 Adapters.


All the adapters work fine under Hypertrm in Windows 11.


But when using the Serial.Open function in C# through System.IO.Ports of .Net4 (identical usage as previously in Windows 10, I can't open the port and get the following exception (see attached image).


I checked the drivers of the CH340 USB to Serial are the newest Version (updated by Windows) and the device is marked running correct in the control panel. See other image attached.


There is one difference I could see in the Windows 11 installation the stack of devices is slightly different in the material configuration. See next image. There is an additional Serenum driver which was not shown on my windows 10 installation.


I have no more idea to get the serial port running on my new Win11 installation, anybody out there who encountered the same problem or anybody who has an idea about this ? Any specialists from microsoft around who could help me with this ?


Best regards



9 Replies

@MMM-IT , I am also facing same issue, have you found any solution for it?

Unfortunately no solution yet. But cool to know I'm not the only one to encounter that problem, seems strange to me, that there is such a bug in an old but still widely used Serial interface in 2023 in Windows 11.

Download the windows 11 latest ch340 driver (3.7.2022.01) and work fine the serial portt under windows 11.

Dear Team,


I am unable to access serial port access and USB to serial access. Could you please share me appropriate driver for windows 11 home version. So that i can able to access my device. 



Akshaya Kumar Behera


Dear Microsoft Support Team,


I am writing to seek assistance regarding a critical issue we are experiencing with serial port access and USB to serial access under Windows 11.


Since upgrading to Windows 11, we have encountered persistent problems that significantly affect our work. Specifically, Working with Serial Port and USB Serial Adapter


These issues are disrupting critical operations that rely on stable serial communication. We have already taken the following steps in an attempt to resolve the problem:


  • Ensured all device drivers are up to date.
  • Tested the hardware on alternative machines running Windows 10, where they function correctly.
  • Checked for any Windows updates or patches that might address known issues with serial ports.

I would greatly appreciate any guidance or support you can provide to resolve these issues. This matter is urgent, as the inability to use serial ports correctly impacts my ability to perform essential tasks. I cannot overstate the importance of your help in this situation.


Please let me know if there are any known issues with serial port access in Windows 11 or if there are specific troubleshooting steps I can follow to rectify the situation. Your prompt response will be highly appreciated.


Thank you for your attention and assistance. Your help in resolving this issue is greatly appreciated.


Best regards,

Amit Kumar Agrawal
+91 - 8008228107

@vista972 I tried with driver provided by you but still it’s not working.

I tried the older driver available here:

And this seemed to work for Windows 11. Weird that an old driver works better than the latest one.


I have the PL-2303 TA chipset.