Is't possible to change app start address from prebuild binary file?

[kaiwak]

Hi,
Usually we set FLASH_START macro to indicate application start address,
I do like to consult is't possible to change the FLASH_START from prebuild binary file without rebuild?

I'm trying to implement dual boot, that is, 2 different application are programed to 2 address of flash,
then boot to one of them depending on bootloader choice,

For example, app1 start from 0x27000, app2 start from 0x8d000,
I set FLASH_START=0x27000 for app1,
FLASH_START=0x8d000 for app2,
then build hex files and program them to flash.

That works but I need to decide application start address before compiling,
I hope the start address can be set by bootloader dynamically,
if application is programed to address of app1, set it to 0x27000, otherwise 0x8d000,
is't possible?

Thanks~

[Jørgen Holmefjord]

Hi,

It is possible to change the start address of the HEX-file using objcopy:

arm-none-eabi-objcopy --change-addresses <address> <input_file>.hex <output_file>.hex

However, I'm not sure if the application will work correctly if moved this way. You may try it out in your device.

Best regards,
Jørgen

[kaiwak]

Hi Jørgen,

Thank you for the reply, exactly arm-none-eabi-objcopy can change the image placement,
then I did some experimentation,

Build image demos_27000.hex with FLASH_START=0x27000,

Change generated hex file address to 0x8d000, named 27000_to_8d000.hex

arm-none-eabi-objcopy --change-address 0x66000 demos_27000.hex 27000_to_8d000.hex
(0x66000 + 0x27000 = 0x8d000)

Write 2 hex files to nRF52840, then seems it can boot to both 0x27000 and 0x8d000,

BUT,
If I erase the image of 0x27000 from nRF52840, keep others,
then it can't boot to image of 0x8d000, the 27000_to_8d000.hex anymore.

I did one more experimentation,
Build an image with FLASH_START=0x00000, then change its address to 0x8d000, named 00000_to_8d000.hex,

arm-none-eabi-objcopy --change-address 0x8d000 demos_00000.hex 00000_to_8d000.hex

Then write original demos_27000.hex and 00000_to_8d000.hex to nRF52840,
this time, 0x27000 can boot normally, but 0x8d000, the 00000_to_8d000.hex can't,

I guess that should be something such like vector table or somethings
are indicated with FLASH_START during compiling,
so even I changed where the image to be writen, image still can't work.

By the way, my arm-none-eabi-objcopy version is 2.34

arm-none-eabi-objcopy --version
GNU objcopy (2.34-4ubuntu1+13ubuntu1) 2.34
Copyright (C) 2020 Free Software Foundation, Inc.
This program is free software; you may redistribute it under the terms of
the GNU General Public License version 3 or (at your option) any later version.
This program has absolutely no warranty.

And, if build image with FLASH_START=0x8d000,
it can boot even image of 0x27000 has been erased.

Thanks~