RTOS: Overview

Chen Weixiang @ Jun 19, 2016 | TAG: RTOS

This article introduces the basic knowledge of Real-Time Operating System (RTOS).

What’s RTOS?

A real-time operating system (RTOS) is an operating system (OS) intended to serve real-time application process data as it comes in, typically without buffering delays. Processing time requirements (including any OS delay) are measured in tenths of seconds or shorter.

A key characteristic of a RTOS is the level of its consistency concerning the amount of time it takes to accept and complete an application’s task; the variability is jitter. A hard real-time operating system has less jitter than a soft real-time operating system. The chief design goal is not high throughput, but rather a guarantee of a soft or hard performance category. A RTOS that can usually or generally meet a deadline is a soft real-time OS, but if it can meet a deadline deterministically it is a hard real-time OS.

A RTOS has an advanced algorithm for scheduling. Scheduler flexibility enables a wider, computer-system orchestration of process priorities, but a real-time operating system is more frequently dedicated to a narrow set of applications. Key factors in a real-time operating system are minimal interrupt latency and minimal thread switching latency; a real-time operating system is valued more for how quickly or how predictably it can respond than for the amount of work it can perform in a given period of time.

List of RTOS

The RTOS is developed and supplied by multiple suppliers in an open market. See the comparison of real-time operating systems for a comprehensive list. Here is a list of RTOS, which are used during my work.

Name License Source Model Target Status Platforms
OSE Proprietary Closed General purpose Active ARM, PowerPC, MIPS, IXP2400, TI OMAP, …
ThreadX Proprietary Available to customers ? Active ARC, ARM/Thumb, AVR32, BlackFin, 680x0-ColdFire, H8-300H, Luminary Micro Stellaris, M-CORE, MicroBlaze, PIC24-dsPIC, PIC32, MIPS, V8xx, Nios II, PowerPC, Renesas RX100, RX200, RX600, RX700, Synergy, SH, SHARC, StarCore, STM32, StrongARM, TMS320C54x, TMS320C6x, x86/x386, XScale, Xtensa/Diamond, ZSP
Micrium µC/OS-II Proprietary Available under license Embedded Active ARM7-9-11/Cortex-M1-3-4-A8/9, AVR, HC11/12/S12, ColdFire, Blackfin, MicroBlaze, NIOS, 8051, x86, Win32, H8S, M16C, M32C, MIPS, 68000, PIC24-dsPIC33-PIC32, MSP430, PowerPC, SH, StarCore, Renesas RX100-200-600-700, RL; STM32, …
Micrium µC/OS-III Proprietary Available under license Embedded Active ARM7-9-11/Cortex-M1-3-4-A8/9, AVR, HC11/12/S12, ColdFire, Blackfin, MicroBlaze, NIOS, 8051, x86, Win32, H8S, M16C, M32C, MIPS, 68000, PIC24/dsPIC33/PIC32, MSP430, PowerPC, SH, StarCore, Renesas RX100-200-600-700, RL; STM32, …

Here is a list of RTOS, which is open source:

Here is a list of RTOS, which is not open source:

  • Ardence RTX
  • BeOS
  • ChorusOS
  • DNIX
  • DMERT
  • e-Tkernel
  • HOPEN OS
  • embOS
  • INTEGRITY
  • ITRON
  • LynxOS
  • MERT
  • MicroC/OS-II
  • MQX RTOS
  • Nucleus
  • OS-9
  • OSE
  • OSEK/VDX
  • OSEKtime
  • PDOS
  • Phar Lap ETS
  • PikeOS
  • Portos
  • pSOS
  • QNX
  • RMX
  • RSX-11
  • RT-11
  • RTOS-UH
  • RTXC
  • Salvo RTOS
  • SINTRAN III
  • Symbian OS
  • ThreadX
  • VRTX
  • VxWorks
  • Windows CE
  • µnOS
  • UNIX-RTR
  • REX
  • HP-1000/RTE

References