Avrdude: ser_open(): can't set com-state for "\\.\COM5" - Possible solution

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Thanks for sharing your finding @t0ny. That is very interesting!

Many users have reported encountering this problem when using cheap Chinese derivative boards from sketchy sellers. Pretty much all of them have reported it was fixed by rolling the CH340 driver back to version 3.7.2022.1:

  1. Click the following link to download the previous version of the driver from an archive of the chip manufacturer's website:
    https://web.archive.org/web/20220519153932/https://www.wch-ic.com/downloads/file/65.html
  2. Wait for the download to finish.
  3. Run the downloaded CH341SER.EXE file.
  4. A "User Account Control" dialog may now appear asking "Do you want to allow this app to make changes to your device?". Click the "Yes" button.
  5. A "DriverSetup(X64)" dialog will open. Click the "INSTALL" button in the dialog.
  6. Wait for the driver installation to finish, as indicated by the appearance of a "Driver install success!" dialog.
  7. Click the "OK" button in the "Driver install success!" dialog.
    The dialog will close.
  8. Click the X icon at the top right of the "DriverSetup(X64)" dialog
    The dialog will close.
  9. Close Arduino IDE if it is running.
  10. Connect the Arduino board to your computer with a USB cable.
  11. Open the Windows Device Manager.
  12. Select View > Devices by type from the Device Manager menus.
  13. Open the "View" menu.
  14. If there is a ✓ to the left of the "Show hidden devices" menu item, click on "Show hidden devices" to disable it.
  15. Open the "Ports (COM & LPT)" section of the Device Manager tree.
  16. You should see a port identified as "USB-SERIAL CH340 (COMn)" under the "Ports (COM & LPT)" section (where "COMn" is some serial port e.g., COM4). Double click on that item.
    The "USB-SERIAL CH340 (COMn) Properties" dialog will open.
  17. Select the "Driver" tab of the "USB-SERIAL CH340 (COMn) Properties" dialog.
  18. You will see a "Roll Back Driver" button in the dialog. If it is not clickable, perform the following instructions:
    1. Click the "Update driver" button.
      An "Update Drivers Device - USB-SERIAL CH340 (COMn)" dialog will open.
    2. Click on "Search automatically for drivers" in the "Update Drivers Device - USB-SERIAL CH340 (COMn)" dialog.
    3. You should now see the driver installation wizard update the driver. Wait for the update to finish, as indicated by the message "Windows has successfully updated your drivers" in the dialog.
      :red_exclamation_mark: It is possible you will instead see the message "The best drivers are already installed". If so, please stop following the instructions here and reply on this forum topic to let us know. I'll provide alternative instructions you can follow.
    4. Click the "Close" button in the "Update Drivers Device - USB-SERIAL CH340 (COMn)" dialog.
      The dialog will close.
  19. Click the "Roll Back Driver" button in the "USB-SERIAL CH340 (COMn) Properties" dialog.
    The "Driver Package rollback" dialog will open.
  20. Click the radio button next to "My apps don't work with this driver" in the "Driver Package rollback" dialog .
  21. Click the "Yes" button.
    The "Driver Package rollback" dialog will close.
  22. Click the "Close" button in the "USB-SERIAL CH340 (COMn) Properties" dialog.

Now start Arduino IDE again and repeat whatever you were doing before when you encountered that error before. Hopefully this time everything will work as expected.

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