https://github.com/stevenreynoso/rtos_task_scheduler_no_library
STM32 Bare-Metal RTOS (Cooperative Task Scheduler)
https://github.com/stevenreynoso/rtos_task_scheduler_no_library
lcd-1602 no-libraries rtos stm32 task-scheduler
Last synced: 3 months ago
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STM32 Bare-Metal RTOS (Cooperative Task Scheduler)
- Host: GitHub
- URL: https://github.com/stevenreynoso/rtos_task_scheduler_no_library
- Owner: StevenReynoso
- Created: 2025-05-06T00:07:29.000Z (5 months ago)
- Default Branch: main
- Last Pushed: 2025-05-06T02:53:16.000Z (5 months ago)
- Last Synced: 2025-06-18T03:37:53.986Z (4 months ago)
- Topics: lcd-1602, no-libraries, rtos, stm32, task-scheduler
- Language: C
- Homepage:
- Size: 42 KB
- Stars: 0
- Watchers: 1
- Forks: 0
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
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README
# STM32 Bare-Metal RTOS (Cooperative Task Scheduler)
This project implements a minimal, no-libraries cooperative RTOS from scratch on the STM32F446RE microcontroller. It manages multiple tasks using a simple round-robin scheduler and displays system output on a 16x2 LCD. All hardware interactions are done through direct register access.
## Features
- Written entirely in C with **no HAL or CMSIS libraries**
- Basic **cooperative multitasking** (3 tasks: LCD print, heartbeat, button press)
- Uses **SysTick** for millisecond timing and task delay control
- LCD1602 display integration via 4-bit GPIO interface
- Button handling on **PA9** with software debounce
- Task scheduling and internal state debugged using **GDB**
## Demo
## Tasks Implemented
| Task Name | Behavior | Interval |
|----------------|----------------------------------|----------|
| task_blink | Displays "Blinking..." | 1000 ms |
| task_heartbeat | Displays "Task 2 is Alive" | 2000 ms |
| task_button_check | Detects button press on PA9 and prints "Button Pressed!" | 50 ms debounce check |
## Tools
- STM32F446RE Nucleo Board
- ARM-GCC toolchain
- GDB for live debugging
- Makefile build system (no IDE bloat)
## How It Works
- Each task is a function with an associated delay and ready flag.
- `SysTick_Handler` increments a global time counter every millisecond.
- `update_task_delays()` is called each loop to check if tasks should be reactivated.
- Tasks self-schedule their next delay inside their own logic.
- `run_scheduler()` loops through task slots and runs ready tasks.
## Getting Started
1. Clone repo
2. Flash to STM32F4 with your preferred tool (ST-Link, OpenOCD, etc.)
3. Connect LCD (PA5–PA8 for data, PA0, PA1, PA10 for control)
4. Connect pushbutton to PA9 and GND
5. Power on and watch tasks rotate live on LCD
## Roadmap
- [ ] Add task state monitor to LCD
- [ ] Implement task counters
- [ ] Add UART logging
- [ ] Support dynamic task creation
- [ ] Preemptive scheduling via timer ISR
## Author
Steven Reynoso
M.S. Computer Engineering, University of Michigan - Dearborn
https://github.com/StevenReynoso