Updating Softdevice with custom bootloader

[marklander]

Hi guys,

i am using a custom UART bootloader ( no double image, just overwrite application due to memory limitations ) on nrf52805 and SD112 7.2.0, a question:

at the moment I am protecting with BPROT registers flash address of bootloader section, but let's say I want to update SD to a new release ( with same size ) is it a good approach to protect with BPROT the first 0x1000 flash page where MBR resides to avoid possible bricks in case of failure of overwrite? I mean i can can the same MBR with a new softdevice release of the same family, hex file comprise both so I am thinking if it's safe to update only SD part of flash above 0x1000.

Thanks!

[Einar Thorsrud]

Hi,

Yes, I would say it is a good idea to protect the MBR page with BPROT. It should never be overwritten. This is done in our example bootloader (which also protects itself with BPROT before starting the application).

To be clear, when you do DFU of a new SoftDevice that will should not contain the MBR, so you must strip out the first page of the SoftDevice hex file. This is done by our tools for use with the example bootloader, and you must do the same for your custom bootloader if updating the SoftDevice. The MBR remains in place, and is responsible for copying in place the new bootloader in case of bootloader updates.

[marklander]

Einar Thorsrud said:

I would say it is a bood idea

It means good? :) or bad?

I suppose it was good...so I could keep the same MBR also to update SD, just need to remove the first 0x1000 part of the .hex file. Right?

[Einar Thorsrud]

marklander said:

It means good? :) or bad?

Sorry, that was I typo (I have fixed it in my previous post). It hsould be "good"

marklander said:

so I could keep the same MBR also to update SD, just need to remove the first 0x1000 part of the .hex file. Right?

Yes, that is correct.