Secure DFU, Should you use fstorage or nrf_dfu_flash

[chris]

Within a buttonless DFU application should nrf_dfu_flash or fstorage be used to erase and write to flash?

SDK 13.0.0 - Soft device s132_nrf52_4.0.2_softdevice running on a nRF52832.

I want to store device specific information (like Serial Number) in flash that the DFU update will not erase. I am following the default DFU memory layout and want to place this information at the end of the application area. DFU_APP_DATA_RESERVED is set to CODE_PAGE_SIZE * 3. My understanding is that this setting will cause the DFU to no erase the last 3 pages of the application area.

[bjorn-spockeli]

If its just a serial number that is written to flash in the application then I would use fstorage as it has a smaller footprint than nrf_dfu_flash that wraps aroung fstorage.

[emdi]

Hi,

That configuration instructs the bootloader to not erase some flash pages which are used by the Peer Manager to store bond information. Thus, the application can retain bond data after a DFU. If you write to that area using fstorage you might end up corrupting the fds data.

In short:

• If you don't use Peer Manager, you can use that area as you wish.
• If use Peer Manager, increase DFU_APP_DATA_RESERVED to include more one flash page and write your data there.