[NRF52] Question about the MBR and SD dependence

[shaba]

Hey folks,

Is there any dependence between the MBR and the SD version? The reason I ask is because we are working on a product that will be able to update the softdevice as well as the app portions of the image while ideally retaining the MBR.

Do you guys see any issues with this method? We are currently running the 2.0.0 version of the 332 SD with the 2.0.0 MBR. I was going to try downgrading just the first page of flash to the old MBR, but figured I would pose the question in parallel.

[bjorn-spockeli]

No, the MBR is SoftDevice independent, so the approach you're describing should work just fine. In fact, this is how we do it in our bootloader, the MBR is never updated during DFU, just the Softdevice.

-Bjørn

[bjorn-spockeli]

Q1: Ease of use. All exceptions are prcessed by the MBR first and then forwarded to the SoftDevice or Bootlaoder. If you only flash the SoftDevice without the MBR, then the exeptions wil not be forwarded to the correct location.

Q2: The MBR simply forwards exceptions to the SoftDevice or the bootloader, see this section in the SoftDevice Specification. You pass execution, using SV calls,see the API doc, to the MBR during Bootloader and SoftDevice updates and the MBR will then perform the swap operation, i.e. swap the old image with the new.