Bare-Metal ARM Cortex-M Driver Architecture

A professional-grade firmware project demonstrating low-level peripheral driver development for the STM32F401RE (ARM Cortex-M4). This project bypasses all vendor abstraction layers (HAL/LL) to interface directly with hardware registers, showcasing deep understanding of MCU architecture and memory-mapped I/O.

🎯 Project Objectives

• Hardware Abstraction from Scratch: Develop modular C drivers by mapping peripheral register structures to physical memory addresses.
• Register-Level Manipulation: Implement bitwise operations for peripheral configuration, clock gating, and data management.
• Industry Standard Workflow: Utilize a professional toolchain including GCC ARM Cross-Compiler and STM32CubeIDE for development and debugging.

🛠 Tech Stack

• Language: Pure C (ISO C11)
• Architecture: ARM Cortex-M4F
• IDE: STM32CubeIDE
• Toolchain: GNU Arm Embedded Toolchain (arm-none-eabi)
• Version Control: Git

🚀 Key Features Implemented

1. Custom Hardware Header (stm32f401xe.h)

• Manually defined peripheral base addresses for AHB/APB buses.
• Mapped GPIO register structures using volatile keyword to ensure thread-safe hardware access and prevent compiler optimization errors.

2. GPIO Driver

• Implemented Clock Gating via RCC (Reset and Clock Control).
• Configured Pin Modes (Input, Output, Alternate Function, Analog) using bit-masking.
• High-performance pin toggling utilizing the ODR (Output Data Register).

💻 How to Build

1. Import the project into STM32CubeIDE.
2. Right-click on the project in the Project Explorer.
3. Select Build Project.
4. The output .elf and .bin files will be generated in the Debug/ or Release/ directory.

📂 Project Structure

.
├── Inc/
│   └── stm32f401xe.h         # Custom register definitions & memory map
├── Src/
│   ├── main.c                # Application logic & peripheral initialization
│   ├── syscalls.c            # Standard system calls for ARM
│   └── sysmem.c              # Memory management for the toolchain
├── Startup/
│   └── startup_stm32f401.s   # Assembly startup code (Vector table & Reset handler)
├── .gitignore                # Optimized to exclude build artifacts
├── STM32F401RETX_FLASH.ld    # Linker script for Flash memory layout
├── STM32F401RETX_RAM.ld      # Linker script for RAM layout
└── README.md                 # Project documentation