nRF52840 (XIAO form factor) USB and DFU detection issue during development

[Daniel DSouza]

Hello everyone,

I’m working with an nRF52840-based board (XIAO form factor) and facing an issue related to USB enumeration and DFU mode detection during development.

Board reference: https://robocraze.com/products/seeed-studio-xiao-nrf52840-development-board-supports-bluetooth-5-0

Issue details:

• USB is not consistently detected after flashing custom firmware
• Board sometimes requires manual reset to be recognized by the host
• Tested on Windows and Linux
• Using nRF Connect SDK with default USB and clock configuration
• External debugger works, but USB CDC/DFU behavior is inconsistent
• I’d like to understand:
• Are there any recommended clock or USB power configurations specific to compact nRF52840 boards?
• Is there a known dependency between bootloader/DFU settings and USB stability on this MCU?
• Any best practices to avoid losing USB access after flashing?

I’m still getting familiar with the Nordic ecosystem, so any guidance or pointers to documentation would be greatly appreciated.

Thanks in advance.

[Turbo J]

Default clock config for the DK is not expected to work on a custom module.

Check module documentation for proper clock and DC/DC settings, no idea what is required for your specific module.

[Simonr]

Hi

As Turbo J says, most third party modules do not run our nRF Connect SDK samples without modifications, as they usually do not have the necessary components for the DCDC regulator and 32.768kHz crystal mounted, so please specify if you have configured your application to use the internal RC oscillator and the LDO instead of the DCDC regulator.

Best regards,

Simon