Introduce to RealTime Application Interface for Linux

Nowadays, people is looking for RealTime solutions for their products, since their tasks have to be done very accurately. One more reason is Linux OS usually to be integrated into embedded IC ( Arm, PowerPC, … ). In term of Realtime OS, there are several wellknown Real-Time OS: QNX, VxWorks, RTAI.

VxWorks comes from WindRiver company, is the most expensive and well supported Real-Time commercial product. It has been used for many years in many famous labratory to do some real-time needed experiments like human interactions, … It costs around 4000$ per license. In additions, WindRiver has a university program which can donate to your university for several licenses for 3 years, read more.

I am not familiar with QNX so just have a look at Wikipedia:

As a microkernel-based OS, QNX is based on the idea of running most of the OS in the form of a number of small tasks, known asservers. This differs from the more traditional monolithic kernel, in which the operating system is a single very large program composed of a huge number of “parts” with special abilities. In the case of QNX, the use of a microkernel allows users (developers) to turn off any functionality they do not require without having to change the OS itself; instead, those servers are simply not run.

The system is quite small, with earlier versions fitting on a single floppy disk.

QNX Neutrino (2001) has been ported to a number of platforms and now runs on practically any modern CPU that is used in the embedded market. This includes the PowerPC, x86 family, MIPS, SH-4 and the closely related family of ARM, StrongARM and XScale CPUs.

Those two QNX and VxWorks for commercial purposes and short-time development products, but, by contrast RTAI is the best choice for one who doesn’t want to spend big money, since it supports a lot of platforms. RTAI stands for RealTime Application Interface for Linux, which lets you write applications and runs it in real time (strict timing constraints) for your Linux distributions. In fact, RTAI is not a RealTime OS, it is just a patch for your Linux distributions since Linux OS itself doesn’t have realtime feature. Like Linux OS, RTAI is totally free and having a big community which can support you during developing your system.The famous and wellknown distributor is Roberto.

RTAI Homepage:

At this moment, RTAI supports following architectures:

  • x86 (with and without FPU and TSC)
  • x86_64
  • PowerPC
  • ARM (StrongARM; ARM7: clps711x-family, Cirrus Logic EP7xxx, CS89712, PXA25x)
  • m68k (supporting both MMU and NOMMU cpus)

The latest version is RTAI 3.8 which was released in 02/16/2010.

How to get started ?

I am sure that you will get a lot of issues during playing with RTAI, so you can get supports from serveral sources:

Note: You need to add RTAI certification in your web browser to view RTAI contents, otherwise you can’t access it.

Some useful articles out there:


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