Flash Data Storage: Defining two Instances or flash segments

[m.li]

Hello,

We want to use the flash to store two types of information: application configuration settings (which should be protected during DFU) and temporary data (which can be erased during DFU). Since the bootloader sdk_config settings specifies a number of pages to protect during DFU, we will need to store the temporary data in a different flash segment from the application configuration setting. Is it possible to declare two different segments (or instances) of the Flash Data Storage; one for application data, and one for temporary data?

We have found an another user who also ran into this issue, but there was no resolution: https://devzone.nordicsemi.com/f/nordic-q-a/51225/using-fds-flash-storage-for-user-settings-as-well-as-for-dfu/205718#205718 

Thank you.

[Vidar Berg]

Hello,

FDS does not support multiple instances, unfortunately. Would it be an option to use fstorage for managing the configuration data and FDS for the temporary data? Newer versions of FDS allows you to reserve pages to other modules through the FDS_VIRTUAL_PAGES_RESERVED setting.

And please be aware that allowing overwrite of the FDS section during DFU may lead to problems with re-initialization of the file system when the new application starts up. To avoid problems with this I would recommend that you add a mechanism that fully erases FDS flash pages after the DFU is complete.

[mrono]

Do you really need to separate the two types of data?

Would it be an option to protect everything during DFU, and manually erase the temporary data after the DFU?

[m.li]

In our application, we will need to use a large amount of flash storage for the temporary data (about 400kB). However, if we were to reserve this flash region, we will not have enough flash space to perform dual-bank DFU - a very important feature from a customer usability point of view. As such, we will likely use the customer UICR registers for storing application configuration, and FDS for temporary data. We will take care to fully erase the FDS pages during a DFU.

Thank you for your help.

[Vidar Berg]

That makes sense. UICR is perfect for storing data that's permanent and don't need to be updated.