Open-source alternatives to FreeRTOS Kernel

NuttX is a POSIX-compliant real-time operating system designed for microcontrollers ranging from 8-bit to 64-bit architectures. It provides a deterministic execution environment with a real-time task scheduler and a POSIX embedded kernel to ensure portable code execution across diverse hardware targets. The project distinguishes itself through a comprehensive hardware abstraction layer that provides standardized drivers for I2C, SPI, CAN, and USB across various semiconductor chipsets. It also features an embedded networking stack supporting TCP, UDP, IPv4, and IPv6, alongside industrial proto

RIOT is a real-time operating system designed for resource-constrained microcontrollers. It provides a kernel for managing hardware peripherals, memory, and multitasking on embedded devices, featuring a microcontroller hardware abstraction layer to unify hardware access across different chipsets. The system employs a preemptive tickless task scheduler with priority-based execution to maximize energy efficiency in battery-powered hardware. It also includes an embedded security framework consisting of cryptographic APIs and secure transport protocols to facilitate authenticated over-the-air fir

Lua RTOS for ESP32 is a real-time operating system designed for ESP32 microcontrollers that integrates a lightweight Lua interpreter to manage hardware resources and application logic. It utilizes a micro-kernel architecture to provide preemptive task scheduling, ensuring deterministic timing and reliable concurrency for embedded operations on resource-constrained hardware. The system distinguishes itself by providing a unified hardware abstraction layer that maps high-level programming commands directly to peripheral registers. This allows developers to interact with sensors, actuators, and

Tock is a secure embedded operating system and microcontroller kernel designed to isolate untrusted applications and drivers. It functions as a memory-safe process isolator that uses a combination of hardware memory protection and language-level type safety to execute mutually distrustful applications on bare metal. The system distinguishes itself through a hardware abstraction layer that decouples high-level components from specific microcontroller implementations using standardized traits. It further employs a virtualization layer to allow multiple independent software components to share a

Mbed OS is a real-time operating system designed for connected internet-of-things devices and microcontroller hardware. It provides a fundamental framework that combines a real-time operating system with an embedded security framework, a hardware abstraction layer for controlling sensors and peripherals, and a device management platform for cloud-based orchestration. The system establishes security foundations to protect connected products from unauthorized access and vulnerabilities. It further enables remote monitoring and hardware orchestration by connecting embedded devices to cloud servi

TencentOS-tiny is a real-time operating system for microcontrollers designed to manage task scheduling and resource allocation across various hardware modules. It functions as an embedded platform and modular kernel for deploying real-time software on different chip architectures. The system includes built-in protocol stacks to enable secure data transmission and connectivity between terminal IoT devices and cloud platforms. The project covers real-time task management, embedded software deployment, and microcontroller administration. It utilizes a modular microkernel architecture and a har

LiteOS is a lightweight real-time operating system kernel designed for constrained devices with limited memory and processing power. It provides a foundation for embedded IoT development, focusing on stable and predictable system resource management. The system implements a preemptive task scheduler and interrupt-driven resource management to ensure real-time responsiveness. It incorporates a tickless idle mechanism and optimized sleep-wake cycles to reduce power consumption in battery-powered hardware. The kernel includes capabilities for task synchronization via semaphores and static memor

embedded-notes is a collection of technical study guides and development notes focused on embedded Linux, Linux kernel internals, and C programming. It serves as a reference for embedded systems development and a preparation resource for technical interviews in the field. The project provides detailed documentation on writing device drivers, managing virtual memory, and understanding kernel internals. It also includes guides on IoT network protocols, such as MQTT and TCP/IP, and outlines the architectural details of chip architectures and hardware peripherals. The material covers a broad sur

ZSWatch is a real-time operating system for wearable devices featuring a touch display and Bluetooth Low Energy connectivity. It provides a comprehensive software suite that includes a Bluetooth LE communication stack, an embedded UI framework for round displays, and a complete firmware toolchain for compiling, flashing, and simulating wearable hardware. The project is distinguished by its specialized wearable capabilities, such as a graphical framework for designing reactive screens and watchfaces via a visual editor. It implements a publish-subscribe messaging system to decouple hardware se

Zephyr is a real-time operating system and cross-platform embedded framework designed for resource-constrained hardware architectures. It provides an embedded kernel that manages memory, power consumption, and hardware peripherals across multiple microcontroller architectures. The project utilizes a hardware abstraction layer to decouple high-level kernel services from physical hardware through standardized driver interfaces. It employs a device tree hardware description format and a hierarchical configuration system to optimize binaries and feature sets for specific hardware constraints. Th

Leaf is a game server framework written in Go designed for building multiplayer game backends. It provides a modular backend architecture that organizes server logic into independent modules and includes a concurrent task scheduler for managing ordered, delayed, or recurring functions. The framework features a TCP and WebSocket server that manages simultaneous connections through a single interface. It incorporates a message router capable of decoding Protobuf and JSON data to map incoming network packets to specific internal server modules. The system includes capabilities for multi-protoco

This project is an educational operating system kernel designed to demonstrate the fundamental architectural principles of memory paging and process management. It is implemented as a minimal kernel that serves as a practical reference for building a functioning system from the ground up. The implementation features a preemptive multitasking kernel that switches execution contexts between threads to share a single CPU. It includes an x86 virtual memory manager that uses paging to map virtual addresses to physical memory and isolate processes. The system covers low-level hardware interfacing

This project is an implementation of the Arduino framework for ESP32 microcontrollers, providing a core that enables firmware development using a familiar API. It functions as a microcontroller hardware abstraction layer and a firmware toolchain integration, bridging external development environments to the hardware for compilation and flashing. The system includes an embedded real-time operating system wrapper to manage multi-core execution and task scheduling, alongside a wireless communication suite for TCP/IP networking and Bluetooth Low Energy. It distinguishes itself by providing an obj

This project is a collection of technical documentation and guides designed as a computer architecture explainer. It provides educational resources on how processors and operating systems execute programs, focusing on the fetch-execute cycle and the fundamental relationship between hardware and the kernel. The documentation covers a wide range of low-level system operations, including detailed guides on the executable and linkable binary format, virtual memory management, and kernel-level operations. It specifically explores the mechanics of CPU scheduling, preemptive multitasking, and the us

This project is a freestanding kernel written in Rust that boots on x86 hardware without a standard library. It serves as a low-level system implementation focusing on the creation of a bare metal operating system. The system implements a bootable disk image toolchain that transforms source code into binaries compatible with a bootloader. It features a custom memory allocator for dynamic memory management and an x86 kernel implementation that includes paging, interrupt handling, and VGA text mode. The project covers several core capability areas, including low-level memory management through

fast-check is a property-based testing framework and random data generator designed to verify software invariants by producing a wide range of randomized input data. It functions as a test data fuzzer that executes predicates against high volumes of random inputs to uncover edge cases and critical bugs. The project is distinguished by its ability to perform input-shrinking searches, which reduce complex failing inputs to their simplest form to isolate the exact cause of failure. It provides deterministic seed replay to exactly reproduce specific test failures and includes a concurrency testin

This project is flight control autopilot software designed as a real-time operating system for managing the flight dynamics and navigation of autonomous multicopters, fixed-wing aircraft, and rovers. It serves as a multi-vehicle autopilot framework that supports various aircraft configurations, including vertical takeoff and landing platforms across industrial environments. The system includes a MAVLink communication stack for exchanging telemetry and command data between unmanned vehicles and ground control stations. It also provides a software-in-the-loop flight simulator to test autopilot

ArduinoJson is a C++ library for parsing and manipulating JSON data and MessagePack binary streams on microcontrollers with limited memory and processing power. It provides the core primitives necessary for embedded data serialization and parsing, enabling devices to exchange structured data over serial or network interfaces. The library is distinguished by its focus on microcontroller memory management, employing strategies such as pool-based allocation, string deduplication, and non-owning string views to minimize RAM usage. It further optimizes for constrained environments by allowing cons

This project is a comprehensive Java backend engineering guide and technical reference focused on high-concurrency design, distributed systems, and microservices architecture. It provides detailed strategies for decomposing monolithic applications, managing service discovery, and implementing the architectural patterns required for scalable backend environments. The repository distinguishes itself through an extensive collection of big data algorithmic references and database scaling strategies. It covers memory-efficient techniques for analyzing massive datasets, such as Top-K element extrac

CppGuide is a curated collection of educational resources and practical guides focused on C++ server development, Linux kernel internals, concurrent programming, network protocols, and security exploitation. It provides structured learning paths for backend developers, covering everything from interview preparation to building high-performance network servers and understanding operating system fundamentals. The guide distinguishes itself by offering in-depth, hands-on tutorials that walk through real-world implementations, including building a Redis-like server from scratch, designing custom

Cpp-taskflow is a C++ task-parallelism framework and task graph scheduler designed to manage and execute complex dependency graphs of parallel tasks across CPU and GPU hardware. It provides a parallel algorithm library for high-performance implementations of reductions, sorts, pipelines, and iterations. The framework distinguishes itself through its ability to offload heavy computational workloads from a task graph to graphics processors for acceleration. It also includes a task profiling tool and a performance analysis interface for visualizing task execution flow and dependency structures t

BASIC-M6502 is a BASIC language implementation for 8-bit microprocessors. It provides an execution environment that allows programs written in a high-level, English-like language to run on 6502 hardware, featuring support for mathematical functions and floating-point arithmetic. The project is designed for cross-platform hardware porting, using conditional compilation and macros to adapt a single codebase across different retrocomputing systems. It utilizes hardware abstraction layers to manage character-based input and output routines. The system includes embedded memory management with dyn

Chronicle Queue is a high-performance data handling system featuring off-heap message queues, memory-mapped file stores, and replicated message stores. It provides a binary compatible memory layout that enables different programming languages to share data without serialization overhead. The system utilizes a replicated message store to synchronize data across multiple nodes, ensuring high availability and instant failover. Its memory-mapped architecture supports deterministic replay from disk and low-latency data recording. The project implements off-heap memory management and zero-allocati

定时任务管理系统

This project is a technical reference and a collection of internal analysis notes focused on the Go language runtime and compiler. It provides a detailed breakdown of the language internals, covering memory management, garbage collection, and the execution model of the scheduler. The material distinguishes itself by providing deep dives into low-level system details, including a reference for Go assembly instructions, register usage, and system call interfacing. It specifically analyzes the internal implementation of concurrency primitives, such as the goroutine scheduling mechanism, channel

nix is a Unix system API library and Rust system programming interface that provides type-safe bindings for invoking low-level system calls. It serves as a low-level operating system wrapper and POSIX compatibility layer, allowing for kernel interactions and administrative tasks through safe wrappers around platform-specific APIs. The project provides a kernel device interface for controlling hardware devices, managing kernel modules, and configuring terminal interfaces. It differentiates itself by offering type-safe wrappers for memory mapping and zero-copy input-output operations to reduce

Bitwise is a computer architecture education kit and a comprehensive set of guides for building a custom CPU, operating system, and compiler from scratch. It serves as a CPU design tutorial and a practical framework for implementing a unique instruction set architecture. The project provides a custom instruction set architecture toolchain, including resources for creating a matching assembler and compiler. It further includes a hardware development guide for synthesizing computer components and peripheral controllers for deployment on programmable logic devices and FPGAs. The kit covers full