Hi,
I built a custom board similar to the Arduino Nano 33Ble (nRF52840 cpu, MBED OS, 1Mb flash).
I implemented a bootloader with VisualMicro, I would like to install it instead of the Arduino bootloader, so I imagine at address 0x00, using a Segger j-link mini edu SWD programmer.

Then this, using the _start_application(0x000668A0) instruction, continue by launching the actual application.

With various attempts (modifying the link file linker_script.ld, board.txt, etc) I am unable to start our bootloader.

Can someone help me ?
Tanks


(0x00)-------bootloader --------------| (0x0668A0)------------------------------------------|

thanks for the quick response.
Among various attempts, I had added an entry to the project's board.txt to force the starting address to 0x0  (which I don't remember).   Then I reported it as original, i.e. empty:

board.txt local:

# micro_boot build property overrides
#

I attach the board.txt of the ...AppData\Local\Arduino15\packages\arduino\hardware\mbed_nano\4.1.3 folder   but I have not modified it.

I made an attempt to edit the file DUINO_NANO33BLE\linker_script.ld :

original:

MEMORY
{
   FLASH (rx) : ORIGIN = 0x10000, LENGTH = 0xf0000
   ........

modified:

MEMORY
{
   FLASH (rx) : ORIGIN = 0x00000, LENGTH = 0xf0000
   ........

but it did not work. Restored to the original.

I also confirm that I always use complete paths.
The only thing, I always work with .bin files and not .hex.
Could it be a problem?

From your observation maybe I should work on the project's board.txt file. If you think that's the way to go, could you give me some advice on how to do it?

Thank you