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Startup

The StartUp module is a fundamental component of the embedded system that ensures proper initialization of the microcontroller immediately after a reset or power-up. This module prepares the hardware and memory environment before handing control over to the user-defined main() function.

Purpose​

The StartUp module is responsible for setting up the essential environment required for the application to run correctly. It is tightly coupled with the microcontroller’s architecture and typically executes directly after the reset vector is triggered.

Features​

  • Stack Pointer and Vector Table Initialization
    Sets the initial stack pointer and configures the interrupt vector table to ensure correct exception and interrupt handling.

  • Memory Section Initialization
    Copies initialized data from flash to RAM and clears the .bss section to zero-initialize uninitialized variables.

  • Constructor Execution
    Automatically calls static constructors (e.g., C++ global objects) before main() is invoked, ensuring proper setup of runtime environments.

  • RCC (Reset and Clock Control) Initialization
    Configures system clocks (HSE, PLL, etc.) to ensure the microcontroller and peripherals operate at the desired frequencies.

  • Main Application Launch
    Transfers execution to the AppMain() function, which contains the user application logic.

Implementation Details​

  • The module typically includes a startup_<device>.s assembly file and C source files for low-level initialization.
  • Standard memory sections handled:
    • .data – copied from flash to RAM
    • .bss – zero-initialized in RAM
  • Custom initialization functions may be provided for clock setup or peripheral preparation.

Dependencies​

  • CMSIS (ARM Cortex-M core support)
  • MCAL (for RCC and NVIC configuration)
  • Linker script (defines memory regions and startup symbols)

Usage​

Include this module at the very beginning of your embedded application. Ensure the vector table and reset handler symbols are defined in the linker script, and that the startup assembly is the entry point in your project.

License​

This project is licensed under the Creative Commons Attribution–NonCommercial 4.0 International (CC BY-NC 4.0).

You are free to use, modify, and share this work for non-commercial purposes, provided appropriate credit is given.

See LICENSE.md for full terms or visit creativecommons.org/licenses/by-nc/4.0.

Authors​

Contributions are welcome! Please open a pull request.