QUERY · ISSUE

SEEED_XIAO_NRF52 board access to 1 MB Flash

openby domisolopened 2025-08-08updated 2025-11-30

enhancementport-nrf

Port, board and/or hardware

XIAO nRF52840 Sense

MicroPython version

MicroPython v1.26.0-preview.527.g593ae04ee on 2025-08-07; XIAO nRF52840 Sense with NRF52840
the same with 1.25.0

Reproduction

stat = os.statvfs("/flash")
(4096, 4096, 64, 59, 59, 0, 0, 0, 0, 255)
So that's 256 kB of memory.

Expected behaviour

No response

Observed behaviour

The board is 256 KB RAM,1MB Flash 2MB onboard Flash
Why does MicroPython only reports 256 kB ?
BTW how do I access both Flash + onboard Flash ? Do I need to make a manual operation in my code?
THanks

Additional Information

No, I've provided everything above.

Code of Conduct

Yes, I agree

CANDIDATE · PULL REQUEST

nrf: Add board definitions for the Seeed XIAO NRF52840 Sense device.

mergedby robert-hhopened 2022-12-09updated 2022-12-18

port-nrf

It keeps compatibility with the XIAO bootloader by:

using Soft Device 7.3.0
reserving 48k memory for the bootloader.

So on double reset a drive pops for uploading an uf2 image or a nrfutil pkg file. Instructions to create it from a hex file are included.

The script download_ble_stack.sh has been adapted to get the version 7.3.0 soft device files. It may have to be executed once before building.

The CPU file system is set to 256k and the pin definitions are adapted. Besides that, it has the common functionality. The on-board sensors and additional flash can be supported by Python scripts.

Assessment

S Sonnet · high

PR #10193 is the PR that originally added board support for the Seeed XIAO NRF52840 Sense, and it explicitly set the CPU filesystem to 256KB as a deliberate design choice for XIAO bootloader compatibility. The PR description states: "The CPU file system is set to 256k and the pin definitions are adapted. Besides that, it has the common functionality. The on-board sensors and additional flash can be supported by Python scripts." This PR is the origin of the limitation the issue reports, not a fix for it. The issue is a feature request to expose the full 1MB internal flash (and 2MB external flash) rather than only 256KB. The PR provides context for why the limitation exists but does not resolve the request.

Suggested action

Leave issue #17867 open. Reference PR #10193 in the issue to explain why the 256KB limit was chosen (XIAO bootloader compatibility with SoftDevice 7.3.0 reserving 48KB). The maintainer should evaluate whether the internal flash filesystem can be expanded beyond 256KB given the bootloader constraints, or whether external flash (2MB) can be mounted as a separate filesystem. The PR's note that "additional flash can be supported by Python scripts" may be sufficient guidance for the user in the near term.