BANK_INVALID_APP set after application has been deleted in single bank DFU?

[ned_zeppelin]

As far as I can tell, the application is set to invalid (settings.bank_0 = BANK_INVALID_APP) after the application has been successfully deleted ( devzone.nordicsemi.com/.../ )?

Would it not be safer to mark the application as invalid before starting the deletion (for single bank DFU)?

We have seen some cases where the application is deleted, but the bank is still valid (making the device "bricked" from a customer's point of view). In my mind, the worst case should be that the application is deleted, but the bootloader enters DFU at startup. Or am I missing something obvious here?

Note that I am using a modified version of the SDK 8.1.0 bootloader (similar to github.com/.../), but the functionality in question seems to be the same for SDK 8.1.0/9.0.0, which are the first recommended single bank DFU versions.

[bjorn-spockeli]

Yes, you are correct, the BANK 0 flag is set to BANK_INVALID_APP after BANK 0 has been erased. I agree that it would be safer to mark BANK 0 as invalid before the erase to avoid the behavior you're describing.

[ned_zeppelin]

OK, thanks.

Is this the case for the current SDK single bank DFU implementation as well?

If so I would request/recommend changing it, as it is a pretty big risk for high volume products (and difficult to notice for users of the SDK).

[bjorn-spockeli]

The bootloader was completly re-written in SDK v12.0.0 and here BANK 0 is invalidated before the erase. This is also the case for all newer SDK versions.

[ned_zeppelin]

Thanks, that's good!