Roger Meier's Forums

Suddenly CoolTerm gives error 31 on Arduino UNO clone with CH340 USB chip.

Using CoolTerm (same settings) on a UNO clone with 16U2 USB it works fine.

Win10 Device Manager reports CH340 driver: 3.9.2024.9 date: 16/09/2024

That looks recent. As I hadn't used the UNO for some time possibly it's a driver update issue.
But here's the kicker. When I run Tera Term on the CH340 UNO that CoolTerm didn't like, it connects OK.

There's no 'roll back' option on the Win CH340 driver so I can't test that.

I'm puzzled why Tera Term should work on the CH340 UNO (if a driver issue) but not CoolTerm.

I updated CoolTerm to the latest version. Problem remains. Is there anything I could try? Thanks.

Hi,

Tera Term might be using a different serial API than CoolTerm does, and it might even use its own proprietary drivers under the hood.

Error 31 usually means that the necessary driver can't be accessed, possibly due to something getting corrupted. Instead of rolling back, I recommend uninstalling the driver via the Device Manager, and then re-installing it.

I hope this helps.

Roger

Thanks for the reply.

I uninstalled the driver as suggested (there was no roll-back option). Didn't help.

Dug through my parts box and found another UNO clone with CH340. CoolTerm connected to that OK. So a difference between the boards.

To rule out the new driver, I found the driver I originally used (ver 3.5.2019.1 date 30/01/2019).

Installing the old driver and running it on the problem board, CoolTerm now connects and works as it originally did!

At this point I can only guess where the fault lies, however the old driver seems to have fixed the problem.

Thanks for your suggestions.

Great! I'm glad you got it working.

Roger

My joy was short-lived when I found Windows Update wanted to reinstall the new CH340 driver.

Googling I discovered the following post in the Arduino forum. It appears not all CH340 chips were made equal which explained my results.

https://forum.arduino.cc/t/how-do-i-pre ... /1257661/2

In my case all that was needed was to allow Windows to make the update - at which point the roll-back option became available.
Executing roll-back there's an option to prevent Windows updating the driver in the future. Fingers crossed!

Users following the Arduino post should note the CH340 driver linked to is dated 2022.

Hopefully this is of help to any CoolTerm users affected. Regards.

Thanks for posting back. This is good information!