Is there any document to introduce the developing with B0? base on nrf connect SDK.

[henrikzhou]

to release  more flash for homekit product, we want to change  2 Slot of B0 from the same size  to diffrent size。 the smaller one run DFU code , the other run application  code.Is there any document to introduce the developing with B0? or is  anyone who try it before?

[Einar Thorsrud]

Hi,

The basic principles of the bootloader chain (including the nRF Secure Immutable Bootloader which was previously referred to as B0) is explained under Secure bootloader chain.

I did not understand the specific question though, so if this does not answer it, perhaps you can rephrase it or elaborate?

[henrikzhou]

PRD  APP:product application code  without DFU function
DFU APP:userdefine DFU application
B0-New: userdefined NSIB,choose  PRD APP or DFU APP to run

When product need to DFU ,PRD APP write a OTA flag into Storage sector,then reboot to B0-New,B0-New choose  PRD APP or DFU APP to run with OTA flag .
 DFU APP will erase S0 sector and update new PRD APP image into S0 sector.Finally, DFU APP reboot to PRD APP。

there are some question:

1. how to fix DFU APP image in S1 sector?

2. is there any document to introduce the Compilation process and script?

[Einar Thorsrud]

Hi,

I am afraid I still don't understand. The code only runs from one slot, and during transport, the new image is loaded into slot S1, and then during activation it is copied to S0. So it does not make sense to have a different size in the two slots (you will never be able to upload an image that is larger than the smallest slot via DFU). If you don't have enough room for 2 times your full application in the internal flash, you will need to add external flash in order to support DFU.

[henrikzhou]

thank you for your advise.