DFU upgrade bootloader and softdevice use single bank

[MR.liu]

I want achieve DFU upgrade bootloader and softdevice use single bank,my SDK is 9.0.0,is it possible?What should i do?

[bjorn-spockeli]

Yes, bootloader and Softdevice updates will always be updated using the dual-bank approach, eventhough you're using a single bank bootloader. The bootloader will not erase the old SoftDevice or bootloader untill the new image has been correctly received and its integrity checked. A single bank bootloader will only be singlebank for application updates, i.e. it will erase the old application to make rrom for the new appliaction.

However, keep in mind that the application will be erased when performing a SoftDevice + Bootloader update so you have to DFU in the application after the SD+BL update.

[bjorn-spockeli]

You cannot erase the old SoftDevice before you have received the new SoftDevice image since you're using the old SoftDevice to receive the new SoftDevice over BLE. The bootloader performs the switch and controls the DFU process so that cannot be erased before the new images have been received.