Guidance Required for Simultaneous Network Core (HCI) FOTA on nRF5340 Using MCUboot

[Rachita Reddy]

Hi Nordic Support Team,

We are working on an nRF5340-based application using the nRF Connect SDK and would like to implement FOTA for both the application core and the network core (HCI firmware).

Current Setup

• Device: nRF5340

• SDK: nRF Connect SDK

• Bootloader: MCUboot (Sysbuild)

• BLE HCI running on the network core

• FOTA images are downloaded from our cloud server (AWS S3)

From the documentation, we understand that the recommended approach for wireless FOTA is Simultaneous Multi-Image DFU, where both the application core and network core are updated during the same reboot.

We also understand that:

• The application core cannot directly write to network core flash.

• MCUboot transfers the network core image through the PCD library using shared SRAM.

• The network core bootloader (B0n) copies the image from RAM into network core flash and performs verification.

Planned Configuration

We intend to enable the following Sysbuild options:

SB_CONFIG_SECURE_BOOT_NETCORE=y
SB_CONFIG_NETCORE_APP_UPDATE=y
SB_CONFIG_MCUBOOT_NRF53_MULTI_IMAGE_UPDATE=y

For MCUboot, we understand the following options are required:

CONFIG_PCD_APP=y
CONFIG_FLASH_SIMULATOR=y
CONFIG_FLASH_SIMULATOR_DOUBLE_WRITES=y
CONFIG_BOOT_IMAGE_ACCESS_HOOKS=y
CONFIG_BOOT_IMAGE_ACCESS_HOOK_NRF5340=y
CONFIG_UPDATEABLE_IMAGE_NUMBER=2

We also understand that the partition layout should include:

• mcuboot_primary

• mcuboot_secondary

• mcuboot_primary_1 (RAM / ram_flash)

• mcuboot_secondary_1

• pcd_sram

Questions

1. Is the above configuration sufficient to support simultaneous FOTA for both the application core and the network core?

2. Is there any additional configuration required in Sysbuild, MCUboot, Partition Manager, or the application that is not explicitly mentioned in the documentation?

3. Since our network core only runs the standard Bluetooth HCI firmware supplied with the SDK (no custom application), is simultaneous multi-image DFU still the recommended approach?

4. Are there any reference samples or production-ready examples demonstrating simultaneous application core + network core FOTA using MCUboot?

5. We are currently using image compression:

SB_CONFIG_MCUBOOT_COMPRESSED_IMAGE_SUPPORT=y

The documentation mentions that compressed images currently support only single-image DFU. Does this mean that network core FOTA is completely unsupported when compression is enabled, and therefore image compression must be disabled to perform simultaneous multi-image updates?

6. Once configured correctly, will the generated dfu_application.zip automatically include both the application core image and the network core image, allowing a single FOTA package to update both cores in one reboot?

Any guidance or recommended configuration would be greatly appreciated.

Thank you.

This version is concise, technically accurate, and structured in the format Nordic DevZone engineers typically respond to quickly.