esp-idf/examples/custom_bootloader/bootloader_override
Omar Chebib a79acb413e bootloader: override the 2nd stage bootloader
Add the possibility to have user bootloader components. This is performed
from an application/project, by creating bootloader components. To do so,
it is required to create a `bootloader_component` directory containing
the custom modules to be compiled with the bootloader.

Thanks to this, two solutions are available to override the bootloader now:
- Using hooks within a user bootloader component
- Using a user defined `main` bootloader component to totally override the
  old implementation

Please check the two new examples in `examples/custom_bootloader`

* Closes https://github.com/espressif/esp-idf/issues/7043
2021-07-05 10:25:32 +08:00
..
bootloader_components/main bootloader: override the 2nd stage bootloader 2021-07-05 10:25:32 +08:00
main bootloader: override the 2nd stage bootloader 2021-07-05 10:25:32 +08:00
CMakeLists.txt bootloader: override the 2nd stage bootloader 2021-07-05 10:25:32 +08:00
example_test.py bootloader: override the 2nd stage bootloader 2021-07-05 10:25:32 +08:00
Makefile bootloader: override the 2nd stage bootloader 2021-07-05 10:25:32 +08:00
README.md bootloader: override the 2nd stage bootloader 2021-07-05 10:25:32 +08:00

Bootloader override

(See the README.md file in the upper level for more information about bootloader examples.)

The purpose of this example is to show how to override the second stage bootloader from a regular project.

NOTE: Overriding the bootloader is not supported with Makefile build system, it is only available with CMake.

How to use example

Simply compile it:

idf.py build

And flash it with the following commands:

idf.py flash

This custom bootloader does not do more than the older bootloader, it only prints an extra message on start up:

[boot] Custom bootloader has been initialized correctly.

Organisation of this example

This project contains an application, in the main directory that represents a user program. It also contains a bootloader_components directory that, as it name states, contains a component that will override the current bootloader implementation.

Below is a short explanation of files in the project folder.

├── CMakeLists.txt
├── main
│   ├── CMakeLists.txt
│   └── main.c                 User application
├── bootloader_components
│   └── main
│       ├── component.mk          
│       ├── CMakeLists.txt   
│       ├── ld/
│       │   └── ...
│       └── bootloader_start.c Implementation of the second stage bootloader
└── README.md                  This is the file you are currently reading

As stated in the README.md file in the upper level, when the bootloader components is named main, it overrides the whole second stage bootloader code.