kopia lustrzana https://github.com/espressif/esp-idf
61 wiersze
2.2 KiB
Markdown
61 wiersze
2.2 KiB
Markdown
| Supported Targets | ESP32 | ESP32-C2 | ESP32-C3 | ESP32-S2 | ESP32-S3 |
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| ----------------- | ----- | -------- | -------- | -------- | -------- |
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# Bootloader hooks
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(See the README.md file in the upper level for more information about bootloader examples.)
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The purpose of this example is to show how to add hooks to the 2nd stage bootloader.
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## Usage of this example:
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Simply compile it:
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```
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idf.py build
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```
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Then flash it and open the monitor with the following command:
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```
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idf.py flash monitor
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```
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If everything went well, the bootloader output should be as followed:
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```
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I (24) HOOK: This hook is called BEFORE bootloader initialization
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I (37) boot: [...]
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[...]
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I (60) HOOK: This hook is called AFTER bootloader initialization
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```
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And finally the application will start and show the message:
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```
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User application is loaded and running.
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```
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## Organisation of this example
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This project contains an application, in the `main` directory that represents a user program.
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It also contains a `bootloader_components` that, as it name states, contains a component compiled and linked with the bootloader.
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Below is a short explanation of files in the project folder.
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```
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├── CMakeLists.txt
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├── main
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│ ├── CMakeLists.txt
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│ └── main.c User application
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├── bootloader_components
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│ └── my_boot_hooks
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│ ├── CMakeLists.txt
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│ └── hooks.c Implementation of the hooks to execute on boot
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└── README.md This is the file you are currently reading
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```
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Bootloader hooks are **not** supported in legacy `make` build system. They are only supported with `CMake` build system.
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## Note about including weak symbols
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The components in ESP-IDF are compiled as static libraries. Moreover, the bootloaders' hooks are declared as `weak`. Thus, when
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defining hooks for the bootloader, we **must** tell the compiler to always include our library (`my_boot_hooks`) in the link process.
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To achieve this, we need to define an extra symbol: `bootloader_hooks_include`. In our case, this symbol is a function defined in
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`bootloader_components/my_boot_hooks/hooks.c`. This will make the linker include all the symbols contained in that file.
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