What is available on the nRF52840 for persistent storage (survives reboot / power cycle)?

[Robert Lasater]

I understand only the flash memory that stores the boot image is available.  We need ca 32 Kb of persistent storage.  How can that flash memory also be used for additional persistent storage?Is there software code to demonstrate read and writing to this persistent storage?

[Robert Lasater]

Followup question: how can a application running on a Nordic board establish the size of the bootloader in flash memory?

[Marte Myrvold]

Hi,

The size of the bootloader is found by reading BOOTLOADER_START_ADDR, which is in UICR @0x10001014. You can find this by looking at the memory layout here.

The total size of flash can be found by reading out code page size and code size from FICR, using NRF_FICR->CODEPAGESIZE and NRF_FICR->CODESIZE.

The reason the two addresses are hard coded is because when using fstorage you choose which space you want to use, which in this case is from 0x3E000 to 0x40000.

You can also use Flash Data Storage (FDS) on top of fstorage. This is recommended because the data will then automatically be stored under the bootloader, or at the end of flash if there is no bootloader. FDS will also handle when data is updated, while with fstorage you must handle it yourself in an app.

Best regards,

Marte