XIAO nrf52840 - can flash, but code will not run (flash location)

RE: XIAO nrf52840 - can flash, but code will not run (flash location)

Menon — Thu, 05 Mar 2026 19:35:45 GMT

Hello,

Good to hear that!

Kind Regards,

Abhijith

RE: XIAO nrf52840 - can flash, but code will not run (flash location)

cgc17 — Thu, 05 Mar 2026 18:59:42 GMT

That gave me a good pointer. Since in my case I am going without a bootloader, I just set `CONFIG_USE_DT_CODE_PARTITION=n` and disabled sysbuild (this was the key) and then it worked! I didn't end up needing the overlay or any other settings as that put it right at the start of flash.

`SB_CONFIG_PARTITION_MANAGER=n` gave me an error for some reason so I did not use that; I'm not sure why it didn't work.

Going forward I now know about the pm_static.yml if I need any custom definitions or need sysbuild then I will take that route. Thanks for your help!

RE: XIAO nrf52840 - can flash, but code will not run (flash location)

Menon — Wed, 04 Mar 2026 18:41:40 GMT

Hello,

For the XIAO BLE board, the default partition layout is defined in the board’s pm_static.yml file. They are configured by Partition Manager, which is enabled by default when building with sysbuild.

So you can either provide your own pm_static.yml or disable the partition manager (SB_CONFIG_PARTITION_MANAGER=n) to use a different partition layout.

Kind Regards,

Abhijith

RE: XIAO nrf52840 - can flash, but code will not run (flash location)

cgc17 — Wed, 04 Mar 2026 14:24:57 GMT

Thanks - I added the below deletes before redefining the partitions and everything builds now without any errors/warnings, but for some reason when I flash it it still putting code starting at 0x00027000. Even with the new flash partitions and `CONFIG_USE_DT_CODE_PARTITION=n` (I also tried without this and got the same result).

/delete-node/ &boot_partition;
/delete-node/ &storage_partition;

Maybe I am destined to require the unused bootloader? 🙂

RE: XIAO nrf52840 - can flash, but code will not run (flash location)

Menon — Wed, 04 Mar 2026 13:24:08 GMT

Hello,

This is because the label boot_partition appears in both the board DTS and the overlay you added, which creates a conflict. Try changing the label name of the boot_partition to something else and see if that resolves the issue.

Kind Regards,

Abhijith

RE: XIAO nrf52840 - can flash, but code will not run (flash location)

cgc17 — Tue, 03 Mar 2026 17:31:07 GMT

Thanks for the reply! When flashing and selecting "erase all" via the nrf connect vs code extension it wipes out the bootloader and softdevice (as expected), but I am okay with that if I can get the code to run without it. I tried adding a xiao_ble_nrf52840.overlay file in my project and pasted in the content you provided from `zephyr/dts/vendor/nordic/nrf52840_partition.dtsi`, but I received this error:

> -- Found devicetree overlay: /home/blinky_3/xiao_ble_nrf52840.overlay
devicetree error: Label 'boot_partition' appears on /soc/flash-controller@4001e000/flash@0/partitions/partition@0 and on /soc/flash-controller@4001e000/flash@0/partitions/partition@f4000

Note: if I do reload the bootlader and softdevice with the arduino IDE and then flash with nRF Connect without selecting Erase All, it does work, but, if possible, I'd rather be able to erase as needed and keep things clean since I don't need the bootloader.

RE: XIAO nrf52840 - can flash, but code will not run (flash location)

khelmutlord — Tue, 03 Mar 2026 14:05:34 GMT

Also note that, by default, the XIAO uses "#include <nordic/nrf52840_partition_uf2_sdv7.dtsi>" which expects a UF2 bootloader. Try using the partitions found in "zephyr/dts/vendor/nordic/nrf52840_partition.dtsi" if you are not using the UF2 bootloader.

/*
 * Copyright (c) 2024 Jacob Winther
 *
 * SPDX-License-Identifier: Apache-2.0
 */

/ {
	chosen {
		zephyr,sram = &sram0;
		zephyr,flash = &flash0;
		zephyr,code-partition = &slot0_partition;
	};
};

&flash0 {
	partitions {
		compatible = "fixed-partitions";
		#address-cells = <1>;
		#size-cells = <1>;

		boot_partition: partition@0 {
			label = "mcuboot";
			reg = <0x00000000 0x0000C000>;
		};

		slot0_partition: partition@c000 {
			label = "image-0";
			reg = <0x0000C000 0x00076000>;
		};

		slot1_partition: partition@82000 {
			label = "image-1";
			reg = <0x00082000 0x00076000>;
		};

		/*
		 * The flash starting at 0x000f8000 and ending at
		 * 0x000fffff is reserved for use by the application.
		 */

		/*
		 * Storage partition will be used by FCB/LittleFS/NVS
		 * if enabled.
		 */
		storage_partition: partition@f8000 {
			label = "storage";
			reg = <0x000f8000 0x00008000>;
		};
	};
};

RE: XIAO nrf52840 - can flash, but code will not run (flash location)

Menon — Tue, 03 Mar 2026 09:25:57 GMT

Hello,

Have you removed the default UF2 bootloader that comes preloaded on the XIAO nRF52840? If so, could you explain how you did that?

From your explanation, I understand that you are trying to flash an application with CONFIG_BUILD_OUTPUT_UF2=n so that it overrides the preloaded bootloader. If that is the case, I doubt that setting CONFIG_BUILD_OUTPUT_UF2=n alone is sufficient to achieve this.

Could you try adding CONFIG_FLASH_LOAD_OFFSET=0 in your prj.conf and check whether that makes the application start at address 0x0?

Kind regards,
Abhijith