Name License Description Last updated
FreeRTOS Modified GPL MSP430 ARM AVR ColdFire PIC x86 FreeRTOS is a popular real-time operating system for embedded devices, being ported to 31 microcontrollers. It is distributed under the GPL with an optional exception. 2015-Oct-16
Contiki BSD MSP430 ARM AVR 8051 Contiki is an open source operating system for the Internet of Things. Contiki connects tiny low-cost, low-power microcontrollers to the Internet. 2015-Aug-26
ChibiOS/RT Modified GPL MSP430 AVR ChibiOS is a complete development environment for embedded applications including RTOS, an HAL, peripheral drivers, support files and a development environment. 2016-Jan-23
RTEMS GPL ARM x86 MIPS PowerPC m68k RTEMS is an open source RTOS that supports open standard application programming interfaces such as POSIX. It is used in space flight, medical, networking and many more embedded devices. 2015-Sep-11
NuttX BSD ARM AVR 8051 x86 NuttX is a real-time operating system (RTOS) with an emphasis on standards compliance and small footprint. Scalable from 8-bit to 32-bit microcontroller environments, the primary governing standards in NuttX are Posix and ANSI standards. 2015-Oct-01
RT-Thread GPL x86 MIPS PowerPC RT-Thread is an open source real-time operating system for embedded devices from China. RT-Thread RTOS is a scalable real-time operating system: a tiny kernel for ARM Cortex-M0, Cortex-M3/4, or a full feature system in ARM Cortex-A8, ARM Cortex-A9 DualCor 2015-Feb-01
RTAI GPL ARM x86 PowerPC x86_64 m68k RTAI is the RealTime Application Interface for Linux - which lets you write applications with strict timing constraints for your favourite operating system. The RTAI distribution includes RTAI-Lab, a tool chain to convert block diagrams into RTAI executab 2015-Jan-28
Xenomai GPL ARM x86 PowerPC Xenomai is a real-time development framework cooperating with the Linux kernel, in order to provide a pervasive, interface-agnostic, hard real-time support to user-space applications, seamlessly integrated into the GNU/Linux environment. 2014-Sep-25
TI-RTOS Kernel Other TI-RTOS Kernel (formerly known as SYS/BIOS™) is an advanced, real-time kernel for use in a wide range of DSPs, ARMs, and microcontrollers. 2015-Aug-19
Atomthreads BSD AVR Atomthreads is a free, lightweight, portable, real-time scheduler for embedded systems. 2015-Feb-24
Erika Enterprise Modified GPL MSP430 ARM AVR Erika Enterprise is the first open-source Free RTOS that has been certified OSEK/VDX compliant!. 2015-Mar-07
Freescale MQX Other ARM ColdFire The Freescale MQX Real-Time Operating System (RTOS) provides real-time performance within a small, configurable footprint. The RTOS is tightly integrated with the latest 32-bit MCUs and MPUs from Freescale and is provided with commonly used device drivers 2015-Mar-07
Fusion Embedded RTOS Other ARM PowerPC The Fusion Embedded RTOS (Real-Time Operating System) from Unicoi Systems is a Real-Time OS designed and optimized for networking and media-centric processors. 2015-Mar-08
MARK3 BSD AVR Mark3 is a sophisticated, modern RTOS and application development platform, targeted towards a growing list of today's most compelling embedded devices. 2015-Mar-08
Nut/OS GPL AVR ColdFire Nut/OS is an intentionally simple RTOS for the ATmega128, which provides a minimum of services to run Nut/Net, the TCP/IP stack. 2014-Nov-20
RIOT Modified GPL MSP430 AVR RIOT is an operating system designed for the particular requirements of Internet of Things (IoT) scenarios. 2015-Dec-04
distortos Mozilla Public License Version 2.0 ARM Distortos is an advanced RTOS written in C++11. 2016-Feb-13
BitThunder GNU GPL version 2.0 ARM A Reliable Real-Time Operating System & Application Framework. 2015-Dec-13
DSPnano Other The DSPnano POSIX RTOS supports general purpose MCU, DSP and DSC 16 bit architectures with as little as 1K of RAM and 6K of flash. 2015-Nov-30
Unison Other Unison supports general purpose microcontrollers (MCUs), digital signal processors (DSPs), FPGAs, microprocessors (MPUs) and digital signal controllers (DSCs) 32 bit architectures with as little as 1K of RAM and 2K of flash. 2015-Nov-30
CoActionOS Other CoActionOS is a real-time, embedded operating system for the ARM Cortex-M3 architecture. 2014-Nov-14
BRTOS MIT MSP430 AVR ColdFire PIC BRTOS is a lightweight preemptive real time operating system designed for low end microcontrollers. 2014-Dec-14

RTOSs not under active development ( Not updated for more than 2 years )

Name License Description Last updated
Femto OS GPL AVR Femto OS: RTOS for small MCU's like AVR. 2012-Dec-09
BeRTOS Modified GPL AVR x86 PowerPC x86_64 BeRTOS is a real time open source operating system supplied with drivers and libraries designed for the rapid development of embedded software. 2011-Aug-08
DuinOS Other AVR DuinOS is a small multithreading real time operating system (RTOS), based on the FreeRTOS kernel, for Arduino compatible boards. 2012-Jan-08
eCos GPL ARM MIPS PowerPC eCos is a free open source real-time operating system intended for embedded applications. The highly configurable nature of eCos allows the operating system to be customised to precise application requirements, delivering the best possible run-time perfor 2013-Aug-25
FunkOS Other MSP430 AVR FunkOS is an RTOS for 8-32 bit MCUs including AVR, MSP430, and Cortex M3. Both C and C++ kernels avaiable. Key features include preemption, periodic events, device drivers, and mutex/semaphores. Includes a variety of graphics and filesystem middleware. 2013-Apr-23
Prex BSD ARM x86 Prex is an open source, royalty-free, real-time operating system for embedded systems. It is designed and implemented for resource-constrained systems that require predictable timing behavior. The highly portable code of Prex is written in 100% ANSI C bas 2009-Oct-01
scmRTOS MIT MSP430 AVR scmRTOS stands for Single-Chip Microcontroller Real-Time Operating System. 2012-Dec-01
TNKernel GPL MSP430 ColdFire TNKernel is a compact and very fast real-time kernel for the embedded 32/16/8 bits microprocessors. 2013-Jun-06
Protothreads BSD AVR 8051 Protothreads are extremely lightweight stackless threads designed for severely memory constrained systems. 2005-Apr-08