nrfutil-device.exe fails if a USB-serial adapter is connected to computer

RE: nrfutil-device.exe fails if a USB-serial adapter is connected to computer

Burt — Mon, 09 Feb 2026 16:52:14 GMT

Christian, I have an "STC Auto Programmer" I purchased way back for STM32 work. Using Windows Device Manager I can see that it has the CH340 USB to UART device inside it. That's one of the known problem devices. You might look at Ports under Device Manager to see what your device uses.

Burt

RE: nrfutil-device.exe fails if a USB-serial adapter is connected to computer

Christian Zingl — Mon, 09 Feb 2026 12:41:52 GMT

Hi,

the same issue occurs when a STM32 USB VCP is connected. Observed when using toolchain v3.2.1.

RE: nrfutil-device.exe fails if a USB-serial adapter is connected to computer

Burt — Fri, 09 Jan 2026 12:57:43 GMT

Sorry, ajd, I must have been careless when typing the instructions. Thank you, Jean-Francois for the correction. I'm glad that it all worked out.

Burt

RE: nrfutil-device.exe fails if a USB-serial adapter is connected to computer

ajd — Fri, 09 Jan 2026 11:33:56 GMT

Yes - change of nrfutil package name worked. Thanks for the info.

RE: nrfutil-device.exe fails if a USB-serial adapter is connected to computer

Jean-Francois Thibon — Fri, 09 Jan 2026 10:44:38 GMT

Hello

I think the repair steps work if you just change the package name to from "nrfutil-device" to "device"

so change the steps:
C:\ncs\toolchains\66cdf9b75e\nrfutil\bin> nrfutil uninstall nrfutil-device
C:\ncs\toolchains\66cdf9b75e\nrfutil\bin> nrfutil install nrfutil-device
to:
C:\ncs\toolchains\66cdf9b75e\nrfutil\bin>nrfutil uninstall device
C:\ncs\toolchains\66cdf9b75e\nrfutil\bin>nrfutil install device

I found also that udating the "programmer" using NRF Desktop should solve the problem because this updates nrfutil.
See release note of programmer 4.7.1 herafter:
"4.7.1 - 2025-12-18
Fixed
Updated the bundled nrfutil device command to v2.15.7, which includes a fix to an issue with the device enumeration on Windows."

RE: nrfutil-device.exe fails if a USB-serial adapter is connected to computer

ajd — Fri, 09 Jan 2026 10:04:51 GMT

Those repair steps don't work for me - it fails with "Package is not installed" at the "nrfutil uninstall nrfutil-device" step - and yes I am in the correct folder. Paths and folders match your example, though note also that my version number for nrfutil also differs slightly from yours (8.1.0).

I've taken the simpler step of unplugging the problematic USB-Serial device while programming as that's an option.

Would be nice for this to be fixed properly in a toolchain update - it's clearly a code issue in respect of device enumeration.

RE: nrfutil-device.exe fails if a USB-serial adapter is connected to computer

Burt — Thu, 08 Jan 2026 20:58:52 GMT

Hello ajd. Definitely v3.2.1 has the problem. I don't believe that any USB-Serial device will cause the issue, but definitely it occurs with CH340 and CP2102 devices. Use Windows Device Manager to see if your device is one of those types. You can fix the problem with the technique I showed above. Otherwise wait until a new release.

Burt

RE: nrfutil-device.exe fails if a USB-serial adapter is connected to computer

ajd — Thu, 08 Jan 2026 15:36:12 GMT

Also seeing this problem as soon as toolchain updated to 3.2.1. Same fault occurs if any USB-Serial device is plugged in (in this case a multimeter with USB-Serial control cable connected).

thread 'main' panicked at C:\Users\VssAdministrator\.cargo\git\checkouts\nrf-device-lib-cf1a63c495be42f5\936ac5a\serialport-lister\src\lib.rs:49:60:
called `Option::unwrap()` on a `None` value
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
Error: Subprocess C:\ncs\toolchains\66cdf9b75e\nrfutil\home\bin\nrfutil-device.exe failed with unexpected exit code Some(101)

Existing project, updated (using nRF Connect within VS Code) from version 3.1 to 3.2.1 of SDK and toolchains. VS Code restarted after update, all extensions up to date.

RE: nrfutil-device.exe fails if a USB-serial adapter is connected to computer

Burt — Thu, 01 Jan 2026 18:05:15 GMT

You're welcome, jean-francois. Glad this helped. Happy New Year!

RE: nrfutil-device.exe fails if a USB-serial adapter is connected to computer

Jean-Francois Thibon — Thu, 01 Jan 2026 17:54:22 GMT

Hi Burt,
Thanks a lot !
I am working with a custom board and my computer is connected to the board simutaneously via CP2102 and to a nrf5340DK to flash&debug, using VS Code. I had to disconnect the CP2102 each time to be able to flash, due to this problem with nrfutil, and this was really annoying. I applied the sequence to update nftutil-device as you suggested, and I confirm that it's now ok !
jean-francois

RE: nrfutil-device.exe fails if a USB-serial adapter is connected to computer

Burt — Thu, 25 Dec 2025 02:31:00 GMT

I was playing around with this some more. Now, I can do the following or something very close:

C:\> set NRFUTIL_HOME=\ncs\toolchains\66cdf9b75e\nrfutil\home

C:\> cd \ncs\toolchains\66cdf9b75e\nrfutil\home

C:\ncs\toolchains\66cdf9b75e\nrfutil\home> erase locked

C:\ncs\toolchains\66cdf9b75e\nrfutil\home> cd ..\bin

C:\ncs\toolchains\66cdf9b75e\nrfutil\bin> nrfutil uninstall nrfutil-device

C:\ncs\toolchains\66cdf9b75e\nrfutil\bin> nrfutil install nrfutil-device

C:\ncs\toolchains\66cdf9b75e\nrfutil\bin> cd ..\home

C:\ncs\toolchains\66cdf9b75e\nrfutil\home> type NUL > locked

to get from 2.15.2 to 2.15.7. And it's not that I have an issue with unlocking the toolchain and making a change that can only be helpful--my issue, Ressa, is that I am only one person out of like 77000 that use DevZone and who knows how many more developers are using NS products--so NS needs to have a system in place that gets everybody updated not just the tiny fraction who stumble upon the right DevZone ticket. (Also this has to be done for a number of toolchains, I believe.)

Burt

RE: nrfutil-device.exe fails if a USB-serial adapter is connected to computer

Burt — Wed, 24 Dec 2025 01:49:16 GMT

Grzegorz, and Ressa, I discovered another USB/UART device that also causes the problem when sitting on the bus: CP2102 from Silicon Labs. One of our custom boards uses a CP2102. I should have realized that although my CP2102 based board sits in a box, my colleague has most, or all of our products connected to his computer -- explaining why he had been seeing the problem. But the bell didn't ring until you mentioned that certain models of USB/UART adapters cause the issue, Grzegorz.

Burt

RE: nrfutil-device.exe fails if a USB-serial adapter is connected to computer

Burt — Tue, 23 Dec 2025 23:53:32 GMT

Holy Moly, Grzegorz, I have replicated the problem, using your information. Luckily, I have a CH340 in the house. I plugged it into a USB jack on my Windows 10 computer and got the error as soon as I tried to program my nRF9160DK board. Using v3.2.1 SDK and toolchain.

My colleague tells me that he removed all devices other than the DK board he was trying to flash and that the problem persisted. I don't know if I want to figure that one out! Here, removing the CH340 from the USB bus fixes the issue.

Burt

ps, I will look at Device Manager and regedit as in nrfutil device list command fails - Nordic Q&A - Nordic DevZone - Nordic DevZone and see if I can make heads or tails out of the situation.

RE: nrfutil-device.exe fails if a USB-serial adapter is connected to computer

grzegorz — Tue, 23 Dec 2025 21:49:40 GMT

Ressa, as Burt noted this nrfutil is part of the toolchain, it's not standalone. The toolchain is installed with nRF Connect SDK. I have latest version of nRF Connect SDK which is 3.2.1. The versions are:
nrfutil 8.1.1 (b6089d0 2025-08-21)
nrfutil-device 2.15.2 (3c54c5f 2025-11-13)

The provided update link is about full nrfutil command which works correctly. The problem is with nrfutil-device.

The linked case is not related.

As for the board configurator, it shouldn't show devices which have nothing to do with programming Nordic chips. The usb-serial adapter is not DK board and can't be configured as such. Yes, the problem is not big as I can select proper board. But it shows there is enumeration issue. It must be noted some enumeration isse was recently fixed https://docs.nordicsemi.com/bundle/nrfutil/page/nrfutil-device/CHANGELOG.html

2025-12-01: Version 2.15.6
Fixed

Windows: Fixed issues in the device enumeration that sometimes led to an index out of bounds error. The issue occurred when merging devices belonging to the same container ID. The issue was introduced in v2.15.2.

RE: nrfutil-device.exe fails if a USB-serial adapter is connected to computer

grzegorz — Tue, 23 Dec 2025 21:31:01 GMT

It's a CH340 USB-serial adapter

RE: nrfutil-device.exe fails if a USB-serial adapter is connected to computer

Burt — Tue, 23 Dec 2025 18:12:08 GMT

Ressa, does that update procedure really apply to nrfutil that is pre-packaged with the toolchain? If so, please provide EXACT instructions how one should update the toolchain. I didn't think it was standard procedure to update a particular released toolchain. Things are supposed to be automatic when using VS Code, I believed.

Burt

RE: nrfutil-device.exe fails if a USB-serial adapter is connected to computer

Burt — Tue, 23 Dec 2025 17:58:32 GMT

Hi Grzegorz, a colleague of mine is experiencing the same issue with flashing. Can you add some screenshots showing what Windows Device Manager shows for the Unkown 5 device? I don't know whether or not we have the same problem, but it might help us. Thanks.

Burt

RE: nrfutil-device.exe fails if a USB-serial adapter is connected to computer

Ressa — Mon, 22 Dec 2025 14:58:53 GMT

Hi,

Thanks for contacting us.
Have you tried to update nrfutil to latest version to see if it helps? Installing and upgrading nRF Util commands
Also please make sure VS Code is using latest updated command.
You can also check below line to see what version of device command is used:
nrfutil device --version

A reported case related to that: (+) can not flash nrf54L15 DK with nrf connect vscode extension - Nordic Q&A - Nordic DevZone - Nordic DevZone

* In board configurator you can see all connected devices, so I don't see any problem with that as you need to select your own specific device before proceeding.

Best regards,
Ressa