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~

[Jørgen Holmefjord]

Do both application use the softdevice? See this section in the documentation:

"For the SoftDevice to locate the application interrupt vectors, the application must define its interrupt vector table at the bottom of the Application Flash Region illustrated in Memory resource map. When the base address of the application code is directly after the top address of the SoftDevice, the code can be developed as a standard ARM Cortex -M4 application project with the compiler creating the interrupt vector table."