nRF52832 two applications in memory after secure buttonless DFU update

[IstvanS]

Hello! Is it normal, that there are 2 applications in memory after secure buttonless DFU update? Please see screenshot of memory map:

I used SDK version 16. Shouldn't the old app have been removed and replaced by the new one?

Thanks!

[Vidar Berg]

Hello,

Yes, this is expected. Please take a look at how dual banked updates are performed here: Dual-bank and single-bank updates. However, what's not clear from the illustrations is that the bootloader does not delete the data in bank 1 after replacing the old application. Data in bank 1 will not get overwritten until next time you do DFU.

[IstvanS]

Hi! Yes, the documentation states " If the new application can be activated, it is copied from bank 1 to bank 0". This must happen, because the new app is active and works as usual after the update. But why is it from bank 1 not deleted? Is it normal?

[Vidar Berg]

Yes, it's normal. The bootloader does not assume that pages in bank 1 are erased when you start DFU. In other words, there is no need to erase the image in bank 1 after activation. Is there a particular reason why you want bank 1 to be erased right away?

[IstvanS]

No, it's not a problem at all. I just assumed it'd be deleted, as the picture suggests:

So I wasn't sure if it was normal that bank 1  is not erased after the update, that's all. Thanks for your support!

[Vidar Berg]

Ok, I see. I do agee with you. The illustration gives you the impression that new application in bank 1 is erased as a part of the activation process. What really happens is that the bootloader just marks the data in bank 1 as invalid by updating the bank 1 flag in the Bootloader settings page and thus free the area for future updates.

[IstvanS]

Yes, in that case it's effectively free, so I think the illustration is fine. If you just added those few lines of clarification to the documentation, it would be perfectly clear.