⚙️ STM32-RTOS-ContextSwitch

📖 Project Overview

This project demonstrates a custom real-time kernel on an STM32 microcontroller, with a focus on implementing manual context switching.
The project was initially generated using STM32CubeMX to set up the hardware abstraction (clocks, timers, SysTick), then extended with custom kernel logic and bare-metal control structures.

🧠 Key Features

• Manually implemented context switching on ARM Cortex-M
• Lightweight thread management without external RTOS libraries
• Use of SysTick to trigger task switching
• Register-level control with direct manipulation of stacks and processor state
• Integration of startup code and exception overrides (e.g. PendSV_Handler)
• Minimal footprint – designed for educational and experimental use

📂 Repository Structure

• src/core/src/kernel.c / inc/kernel.h – Core scheduler and task switching logic
• src/core/src/asmDumps.s – Assembly routines for saving/restoring context
• doc/ – Proof pictures of more than one running Thread

⚙️ Technologies Used

• STM32F401 Microcontroller also worked on STM32U575 Microcontroller
• STM32CubeMX – Project and peripheral initialization
• Bare-metal C – Kernel logic and memory management
• ARM Cortex-M Assembly – Manual context saving/restoring
• SysTick Timer – Periodic context switch trigger
• STM32CubeIDE / Keil / GCC – Flexible toolchain support

🚀 How It Works

1. STM32CubeMX initializes the project (clock tree, SysTick, memory layout, vector table).
2. Tasks are manually defined with separate stacks.
3. On each tick, SysTick_Handler triggers the PendSV_Handler for a context switch.
4. asmDumps.s saves registers (e.g., R4–R11) and restores the next task's context.
5. The system returns to thread mode using PSP (Process Stack Pointer).

The project builds a minimal RTOS-like system with manual scheduling, without relying on any third-party RTOS.

🛠️ Getting Started

Requirements

• STM32 board (e.g. STM32F103, STM32F407)
• STM32CubeIDE or alternative ARM GCC toolchain
• ST-Link programmer/debugger
• Optional: UART or GPIO for task status output

Steps

1. Open or regenerate the .ioc file with STM32CubeMX
2. Import project into STM32CubeIDE (or build using Makefile/GCC)
3. Modify kernel.c to define your own threads
4. Build and flash to target board
5. Use debugger or GPIO/UART output to verify task switching

✅ Project Status

✅ Functional Prototype
The system performs reliable context switches between multiple threads.
All switching is implemented using custom logic – no RTOS frameworks involved.

Great base for deeper exploration of embedded RTOS internals.

📄 License

This project is licensed under the MIT License – see the LICENSE file for details.