seL4 is the world’s first operating system kernel with a formal proof of implementation correctness and security enforcement (confidentiality, integrity, availability). It is a high-assurance, high-performance microkernel designed for security and safety-critical systems. Its minimal kernel design minimizes the attack surface, and its capability-based access control mechanism provides fine-grained control over system resources, enabling strong isolation between components. seL4 is developed and maintained by the seL4 Foundation as an open-source project.

uKOS is a multi-tasking OS suitable for small embedded µController systems. It is based on a preventive multitasking scheduler.

Embox is a highly configurable Real-Time Operating System (RTOS) designed for resource-constrained embedded systems. Its core philosophy is enabling the use of familiar Linux software and development paradigms without needing a full Linux kernel. Embox achieves this through strong POSIX compliance and a modular architecture (Mybuild system) allowing developers to select only necessary components. It supports a wide range of architectures and platforms, aiming to bring desktop-like capabilities, including networking, filesystems, GUIs (Qt, LVGL), and various scripting languages, to microcontroller environments.

The Newtron Flash File System (nffs) is an open source file system available by default with the Apache Mynewt OS.

Free, simple and tiny cooperative operating system (OS) designed for deeply embedded applications.

LibreRTOS is a portable single-stack Real Time Operating System. All tasks share the same stack, allowing a large number or tasks to be created even on architectures with low RAM, such as ATmega328P (2kB).

TNeo is a well-formed and carefully tested preemptive real-time kernel for 16- and 32-bits MCUs. It is compact and fast.

CGUI is a library that provides you with a set of C-functions to create GUI applications, i.e. windows and window controls like buttons, check-boxes, menus, input boxes etc.

IUP is a portable toolkit for building graphical user interfaces. It offers a configuration API in three basic languages: C, Lua and LED. IUP purpose is to allow a program to be executed in different systems without any modification.

F9 microkernel is a microkernel-based (L4-style) kernel to support running real-time and time-sharing applications (for example, wireless communications) for ARM Cortex-M series microprocessors with efficiency (performance + power consumption) and security (memory protection + isolated execution) in mind.

EEFS is for EEPROM File System Project (EEFS). It is a simple file system for memory devices such as EEPROM, RAM, ROM, etc. Currently it is not intended for block oriented devices such as disks and flash devices.

FatFs is a generic FAT/exFAT file system module for small embedded systems. The FatFs module is written in compliance with ANSI C (C89) and completely separated from the disk I/O layer. Therefore it is independent of the platform. It can be incorporated into small microcontrollers with limited resource, such as 8051, PIC, AVR, ARM, Z80, 78K and etc.

µGUI is a free and open source graphic library for embedded systems. It is platform-independent and can be easily ported to almost any microcontroller system. As long as the display is capable of showing graphics, µGUI is not restricted to a certain display technology. Therefore, display technologies such as LCD, TFT, E-Paper, LED or OLED are supported.

MiniGUI is a free software project. It aims to provide a fast, stable, and cross-operating-system graphics user interface (GUI) support system, which is especially fit for real-time embedded systems based-on Linux/uClinux, eCos, and other traditional RTOSes, such as VxWorks, ThreadX, uC/OS-II, and Nucleus.

Spiffs is a file system intended for SPI NOR flash devices on embedded targets.

Yaffs (Yet Another Flash File System) is an open-source file system specifically designed to be fast, robust and suitable for embedded use with NAND and NOR Flash.

Apache Mynewt is a community-driven, open-source RTOS designed for highly constrained embedded systems where power and cost are primary concerns. It emphasizes modularity and portability, enabling developers to include only the necessary components for their application. Mynewt features a preemptive real-time kernel, the high-performance Apache NimBLE Bluetooth 5 stack, secure bootloader, and flash filesystems (NFFS, FatFS). Its companion Newt build and package management tool simplifies development, configuration, and deployment across diverse hardware, facilitating fine-grained control over the final firmware image.

A Reliable Real-Time Operating System & Application Framework.

distortos is an object-oriented C++ RTOS for microcontrollers.

mbed OS is an open-source embedded operating system designed specifically for the “things” in the Internet of Things (IoT). It includes all the features you need to develop a connected product based on an ARM Cortex-M microcontroller.