STM32F4 HAL Library (Bare-Metal)

This project is a custom Hardware Abstraction Layer (HAL) for the STM32F4 microcontroller series, specifically designed for the STM32F446RE. It provides direct, register-level control without relying on the STM32 HAL or CMSIS libraries. Built for learning purposes and to show what is going on underneath the hood.

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Features

• GPIO – Configure, read, write, and set alternate functions.
• RCC – Enable peripheral clocks manually.
• SPI – Master mode, full-duplex SPI support.
• Systick – Microsecond and millisecond delay functionality.
• TIM – Timer initialization and basic configuration.
• UART – Transmit, receive, and configure UART communication.

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File Structure

Hal_Library/
├── core/                  # Contains main.c
├── src/                   # All peripheral source files (hal_gpio.c, etc.)
├── include/               # Public headers (hal_gpio.h, etc.)
│   └── registers/         # Peripheral register mappings (stm32f4_gpio.h, etc.)
├── platform/stm32f4/      # Contains Startup file and linker script
├── build/                 # Build artifacts (generated)
├── Makefile               # Build system
└── README.md              # This file

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Getting Started

Dependencies

• arm-none-eabi-gcc
• stlink-tools (provides st-flash and st-util for ST-Link programming/debugging)

Install with:

sudo apt install gcc-arm-none-eabi stlink-tools

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Build Commands

Command	Description
make	Compiles all source files and links the ELF
make clean	Removes the build/ directory
make flash	Flashes the .bin to STM32 via ST-Link
make debug	Launches st-util and opens GDB

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Flashing Notes

• Ensure the STM32 is connected via ST-Link and powered on.
• Flashing uses st-flash. The address 0x08000000 is the flash start.
• You may need sudo depending on udev rules:

sudo make flash

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Debugging Guide

1. Connect your board via USB ST-Link.
2. Start st-util manually.
3. Launch GDB (use gdb-multiarch if needed):

gdb-multiarch build/main.elf

4. In GDB:

(gdb) target extended-remote :4242
(gdb) monitor reset halt
(gdb) continue

Optional GDB commands:

• step (single instruction)
• next (steps through)
• break <function> (set breakpoint)
• info registers (shows registers)
• x/10i $pc (disassemble instructions at PC)

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Doxygen Documentation

To view the generated documentation in your browser, use the helper script:

./open_docs.sh

If the documentation hasn’t been generated yet, run:

doxygen Doxyfile

• Output HTML goes to docs/html/index.html by default.

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Common Issues

"No rule to make target 'startup.s'"

• Cause: Wrong path to startup file.

• Fix: Update STARTUP variable in Makefile:

  STARTUP = platform/stm32f4/startup.s

"undefined reference to main"

• Cause: The linker can't find your main() function.
• Fix: Ensure core/main.c is included in SRC_DIR or explicitly added.

"cannot open file 'st-flash'"

• Cause: ST-Link utilities not installed.

• Fix:

  sudo apt install stlink-tools

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Contribution Notes

This HAL was built for educational purposes and kept intentionally minimal. Contributions, testing, and refactors are welcome. This library avoids all vendor dependencies for clarity and control.

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License

MIT License – Use and modify freely.