Alhamdulillah,,, setelah saya coba berhasil, board sudah mau ngeblink... trims banyak atas bantuaanya > ptillisch... Semoga teman-teman yang mengalami masalah seperti saya cepat teratasi dan bisa mulai berkarya yang bermanfaat... ada tambahan sedikit siapa tau ada manfaatnya bagi teman-teman, tadi setelah berhasil ngeblink, entah apa saya nggak tau penyebabnya tiba-tiba boardnya ngambeg tidak mau ngeblink, ternyata setelah drivernya saya ganti versi WCH340G alhamdulillah berhasil bisa ngeblink lagi dan semoga tidak rewel....
worked like a charm yur my hero
Many thanks for this- worked for me with a Wemos D1 Mini clone , also.
Brilliant... Worked for me. Thanks
Thank you so much. legend
worked for me as well using an ESP32-CAM purchased in 2021, thanks!!!
hello,i have the same problem but in the device i don't have the " USB-SERIAL CH340" name but i have "USB Serial Port (COMn)" name. how can i do?
You saved my day!!! Thanks 
Hi @panetti05. Please try following the instructions from post #4 anyway. When you get to step 16:
Just select the port that is identified as "USB Serial Port (COMn)".
Hopefully that will solve the problem.
The boards that I have produce a port that is named like "USB-SERIAL CH340 (COMn)" in Device Manager. However, I only have boards with legitimate WCH CH340 chips, which don't produce this "PermissionError(13, 'A device attached to the system is not functioning.', None, 31)" error during uploads, even though I have the latest version of the CH340 Windows driver installed on my computer. It might be that the sketchy unlabeled "CH340" chips are identified differently by Device Manager. Unfortunately I haven't managed to get my hands on one of the boards with the unlabeled "CH340" chip, so I am hindered in my ability to provide effective support to the users who are unfortunate enough to have procured one of these troubled cheap Chinese boards.
thanks now it is working
it really worked for me , thanks.
THNX 
Thank you man
Had the unmarked chip as described in your post. This worked for me, Thanks!
hice los pasos descritos e instale un driver anterior y reinicie mi laptop y funciono, gracias
Some (like me) may now find that this link (despite saying v3.8) auto-downloads the v3.9 driver, not allowing you to roll back.
If the link from @ptillisch does not work, use the archived version of v3.7 below:
https://web.archive.org/web/20230217212903/https://www.wch.cn/downloads/file/65.html
Thanks @lights_sound. I confirm that the link in my instructions no longer works to obtain the version 3.7.2022.01 of the driver which is the last one compatible with the sketchy unlabeled "CH340" chips. That is quite unfortunate, but at least the Internet Archive Wayback Machine can save the day!
I confirm that the archive link you shared does provide the download of the 3.7.2022.01 version of the driver that my instructions were intended to obtain.
ПРОСТО еще раз запустите ch34-ser