custom bootloader and s132

RE: custom bootloader and s132

Hung Bui — Mon, 04 Jan 2021 10:12:13 GMT

Hi Anthony,

Yes you are correct. It's a standard to use this file if you plan to use our bootloader or softdevice. The MBR is included inside the softdevice. So in any application that you flash the softdevice the MBR is also flashed.
We don't provide MBR source code, the only purpose of the MBR is to support bootloader functionality and does interrupt vector forwarding.

RE: custom bootloader and s132

AMarch — Wed, 23 Dec 2020 15:04:40 GMT

[quote userid="2121" url="~/f/nordic-q-a/68777/custom-bootloader-and-s132/282076#282076"]If you are developing your own bootloader, I would suggest to locate it to the bottom of the flash, the same way as our bootloader in nRF5 SDK. The MBR when detecting a bootloader (an address in MBR page) will jump to the bootloader instead of executing the softdevice. [/quote]

So , something I am not catching by reading the Bootloader and DFU modules sections of the Infocenter, is the MBR.
If I may add, my additional questions here:
The mbr is a fixed .hex file in the SDK , called mbr_nrf52_2.4.1_mbr.hex , we don't make this file , anywhere , is that correct? This file has no source or project?

From the open_bootloader makefile it appears I need to load this file loaded as well as the boot loader hex.
So it it standard to just use this file?

RE: custom bootloader and s132

snooooopy — Thu, 26 Nov 2020 17:13:32 GMT

Thank you for your time! This answere all my question.

RE: custom bootloader and s132

Hung Bui — Thu, 26 Nov 2020 13:11:56 GMT

Hi Snoooooooooooooopy,

- S132 uses absolute address so it can't be re-located to other location from the designed place (starts right after the MBR (0x1000), which can be consider part of the softdevice and the MBR starts at address 0x0000000)

- If you don't change the version (minor version and major version) the flash requirement of the softdevice unchange. But the RAM requirement is depends on the application configuration (for example how many services, characteristics, size of characteristics etc) will affect the RAM requirement for the softdevice.

- You meant to ensure the softdevice is signed before executing ? Yes you can develop that in your bootloader. We also have that implemented in our bootloader in SDK v17. You can have a look here: https://infocenter.nordicsemi.com/topic/sdk_nrf5_v17.0.2/lib_secure_boot.html?cp=7_1_3_5_0_8_1_2#secure_boot_mode_selection

- You can read more about booting process in the documentation page above. The MBR starts first, then the bootloader, then the softdevice and then the application. The softdevice when initialized will handle the interrupts and only forward those interrupts available for the application to the application.

If you are developing your own bootloader, I would suggest to locate it to the bottom of the flash, the same way as our bootloader in nRF5 SDK. The MBR when detecting a bootloader (an address in MBR page) will jump to the bootloader instead of executing the softdevice.