Bank1 contains old fw image after dual bank OTA.

[terrygreasewel]

NRF52840, SDK, nrf5-sdk-17.

This could be a misunderstanding of how the dual bank update works, however I am finding that after an OTA, Bank0 contains the new fw image but Bank1 contains the old image. My understanding was that Bank1 overwrites Bank0 once it has been validated, and that after the OTA I should only see an image in Bank0. Is this a bug or a feature?

Note: after the OTA the new fw image runs correctly as expected. 

Left image: Before OTA, we see an image of 50kB in Bank0 as expected. 

Right image: After OTA, we see new fw image of 70kB in Bank0, and the previous Bank0 image now in Bank1.

I am wondering if this is normal behavior or if I have modified the bootloader unknowingly as for dual bank updates.

Based on the infocenter, I expected bank1 to be empty after the dual bank OTA: https://infocenter.nordicsemi.com/index.jsp?topic=%2Fsdk_nrf5_v17.0.2%2Flib_bootloader_dfu_banks.html&anchor=lib_bootloader_dfu_appdata

Is there a double switch going on here??

Appreciate the help!

[terrygreasewel]

I think this is just remnants of bank1, not actually the og fw in bank0. Bank0 increased in size so it overwrote what was left in bank1, and bank1 is not erased after the dfu.