A minimal, preemptive Real-Time Operating System kernel built from scratch for ARM Cortex-M processors.
一个从零构建的、面向 ARM Cortex-M 处理器的极简抢占式实时操作系统内核。
- Priority-based preemptive scheduling — 8 priority levels (0 = highest) 基于优先级的抢占式调度 — 8 个优先级（0 = 最高）
- Round-robin for tasks at the same priority level 同优先级任务采用时间片轮转调度
- Configurable time slicing — default 10ms per task 可配置时间片 — 默认每任务 10ms
- Tick timer — 1kHz SysTick for precise timing 滴答定时器 — 1kHz SysTick 精确定时
- Create, delete, suspend, resume tasks 创建、删除、挂起、恢复任务
- Task delay (blocking sleep) 任务延时（阻塞式睡眠）
- Dynamic priority change 动态优先级调整
- Stack overflow detection (via watermark) 栈溢出检测（水位标记法）
- Up to 16 concurrent tasks 最多支持 16 个并发任务
- Mutex with priority inheritance — prevents priority inversion 互斥锁（带优先级继承）— 防止优先级反转
- Semaphore — binary and counting, with timeout 信号量 — 支持二值和计数模式，带超时
- Message Queue — typed inter-task communication, blocking send/receive 消息队列 — 类型化任务间通信，阻塞式收发
- Software timers — one-shot and periodic modes 软件定时器 — 单次和周期模式
- Memory pool — fixed-size block allocator, O(1) alloc/free 内存池 — 固定大小块分配器，O(1) 分配/释放
- ARM Cortex-M3/M4 support
- PendSV context switch (hardware-assisted)
- SysTick tick timer
- C++17 with zero-overhead abstractions
- ~2KB Flash, ~256B RAM (minimal config)
┌──────────────────────────────────────┐
│ Application Tasks │
│ (Producer, Consumer, Logger, ...) │
│ 应用任务层 │
├──────────────────────────────────────┤
│ RTOS Kernel API │
│ ┌────────┐ ┌──────┐ ┌──────────┐ │
│ │Scheduler│ │Mutex │ │ MsgQueue │ │
│ │(8-prio │ │ (PI) │ │ (FIFO) │ │
│ │ RR) │ │ │ │ │ │
│ └───┬────┘ └──┬───┘ └────┬─────┘ │
│ └─────────┼──────────┘ │
│ ┌────▼────┐ │
│ │ PendSV │ Context │
│ │ Handler │ Switch │
│ └─────────┘ │
├──────────────────────────────────────┤
│ Hardware Abstraction Layer (HAL) │
│ 硬件抽象层 │
│ SysTick (1kHz) | PendSV | WFI │
├──────────────────────────────────────┤
│ ARM Cortex-M4 (STM32F4xx) │
│ 168MHz | FPU | NVIC | SysTick │
└──────────────────────────────────────┘
rtos-task-scheduler/
├── include/
│ └── kernel.h # Main API header (C++17) / 主API头文件
├── src/
│ └── kernel.cpp # Kernel implementation / 内核实现
├── port/
│ └── arm_cortex_m/
│ ├── port.h # Hardware registers / 硬件寄存器定义
│ └── port.cpp # Context switch (PendSV ASM) / 上下文切换
├── examples/
│ ├── blink/ # LED blink (basic) / LED闪烁（基础）
│ │ └── main.cpp
│ └── multi_task/ # Producer-Consumer (advanced) / 生产者-消费者（进阶）
│ └── main.cpp
├── linker.ld # STM32F446RE linker script / 链接脚本
├── CMakeLists.txt # Build system / 构建系统
├── toolchain-arm.cmake # Cross-compilation toolchain / 交叉编译工具链
└── Makefile # Convenience build commands / 便捷构建命令
# Install ARM GCC toolchain / 安装 ARM GCC 工具链
# Windows: download from arm.com
# Linux: sudo apt install gcc-arm-none-eabi
# Install ST-Link (for flashing) / 安装 ST-Link（用于烧录）
# https://github.com/stlink-org/stlinkmkdir build && cd build
cmake -DCMAKE_TOOLCHAIN_FILE=../toolchain-arm.cmake ..
make -j4# Flash blink example / 烧录闪烁示例
st-flash write build/blink.bin 0x08000000
# Flash multi-task example / 烧录多任务示例
st-flash write build/multi_task.bin 0x08000000#include "kernel.h"
void taskBlink(void*) {
while (true) {
setLED(true);
rtos::taskDelayMs(500);
setLED(false);
rtos::taskDelayMs(500);
}
}
int main() {
rtos::kernelInit();
rtos::TaskConfig cfg;
cfg.name = "blink";
cfg.func = taskBlink;
cfg.stackSize = 256;
cfg.priority = 2;
rtos::taskCreate(cfg);
rtos::kernelStart(); // Never returns / 永不返回
}rtos::Mutex* mtx;
rtos::mutexCreate(&mtx);
void taskA(void*) {
while (true) {
rtos::mutexLock(mtx);
// Critical section - priority automatically boosted
// 临界区 — 如果有更高优先级任务在等待，优先级会自动提升
rtos::mutexUnlock(mtx);
rtos::taskDelayMs(100);
}
}struct Data { float temp; float hum; };
Data buffer[10];
rtos::MsgQueue* mq;
rtos::msgqCreate(&mq, buffer, sizeof(Data), 10);
void producer(void*) {
Data d = {25.5f, 60.0f};
rtos::msgqSend(mq, &d); // Blocks if full / 队列满时阻塞
}
void consumer(void*) {
Data d;
rtos::msgqReceive(mq, &d, 1000); // 1s timeout / 1秒超时
}void onTimer(void*) {
// Runs every 1000ms / 每1000ms执行一次
toggleLED();
}
rtos::Timer* tmr;
rtos::timerCreate(&tmr, onTimer, nullptr, 1000, rtos::TimerMode::PERIODIC);
rtos::timerStart(tmr);taskCreate(config, &id)— Create a new task / 创建新任务taskDelete(id)— Delete a task / 删除任务taskSuspend(id)— Suspend a task / 挂起任务taskResume(id)— Resume a suspended task / 恢复任务taskDelayMs(ms)— Sleep for N milliseconds / 睡眠 N 毫秒taskSetPriority(id, prio)— Change task priority / 更改任务优先级
mutexCreate(&mtx)— Create mutex / 创建互斥锁mutexLock(mtx, timeout)— Lock (with priority inheritance) / 加锁（带优先级继承）mutexUnlock(mtx)— Unlock / 解锁
semCreate(&sem, initial, max)— Create semaphore / 创建信号量semWait(sem, timeout)— Wait (decrement) / 等待（减操作）semPost(sem)— Signal (increment) / 释放（加操作）
msgqCreate(&mq, buf, size, cap)— Create queue / 创建队列msgqSend(mq, msg, timeout)— Send message / 发送消息msgqReceive(mq, msg, timeout)— Receive message / 接收消息
timerCreate(&tmr, cb, ctx, ms, mode)— Create timer / 创建定时器timerStart(tmr)— Start timer / 启动定时器timerStop(tmr)— Stop timer / 停止定时器
- STM32F4xx (tested on STM32F446RE) / STM32F4xx（在 STM32F446RE 上测试）
- ARM Cortex-M4 with FPU / 带 FPU 的 ARM Cortex-M4
- 168MHz clock / 168MHz 时钟
- ST-Link debugger / ST-Link 调试器
MIT License
Isaac — Diploma in Electronic Engineering, TAR UMT
Built with ❤️ for learning RTOS internals 用 ❤️ 构建，用于学习 RTOS 内部原理