Real-time application interface (RTAI) is a
real-time
Real-time or real time describes various operations in computing or other processes that must guarantee response times within a specified time (deadline), usually a relatively short time. A real-time process is generally one that happens in defined ...
extension for the
Linux kernel, which lets users write applications with strict timing constraints for Linux. Like Linux itself the RTAI software is a community effort. RTAI provides deterministic response to interrupts,
POSIX
The Portable Operating System Interface (POSIX) is a family of standards specified by the IEEE Computer Society for maintaining compatibility between operating systems. POSIX defines both the system- and user-level application programming inter ...
-compliant and native RTAI real-time tasks. RTAI supports several architectures, including
IA-32
IA-32 (short for "Intel Architecture, 32-bit", commonly called i386) is the 32-bit version of the x86 instruction set architecture, designed by Intel and first implemented in the 80386 microprocessor in 1985. IA-32 is the first incarnation o ...
(with and without
FPU and
TSC TSC may refer to:
Organizations
* Technology Service Corporation, a US engineering company
* Terrorist Screening Center, a division of the National Security Branch of the US Federal Bureau of Investigation
* The Shopping Channel, a Canadian televi ...
),
x86-64
x86-64 (also known as x64, x86_64, AMD64, and Intel 64) is a 64-bit version of the x86 instruction set, first released in 1999. It introduced two new modes of operation, 64-bit mode and compatibility mode, along with a new 4-level paging ...
,
PowerPC,
ARM
In human anatomy, the arm refers to the upper limb in common usage, although academically the term specifically means the upper arm between the glenohumeral joint (shoulder joint) and the elbow joint. The distal part of the upper limb between th ...
(
StrongARM
The StrongARM is a family of computer microprocessors developed by Digital Equipment Corporation and manufactured in the late 1990s which implemented the ARM architecture, ARM v4 instruction set architecture. It was later acquired by Intel in ...
and
ARM7
ARM7 is a group of 32-bit RISC ARM processor cores licensed by ARM Holdings for microcontroller use. The ARM7 core family consists of ARM700, ARM710, ARM7DI, ARM710a, ARM720T, ARM740T, ARM710T, ARM7TDMI, ARM7TDMI-S, ARM7EJ-S. The ARM7TDMI a ...
: clps711x-family,
Cirrus Logic EP7xxx, CS89712, PXA25x), and
MIPS.
RTAI consists mainly of two parts: an
Adeos
ADEOS I (Advanced Earth Observing Satellite 1) was an Earth observation satellite launched by NASDA in 1996. The mission's Japanese name, Midori means "green". The mission ended in July 1997 after the satellite sustained structural damage to th ...
-based patch to the Linux kernel which introduces a hardware abstraction layer, and a broad variety of services which make lives of real-time programmers easier. RTAI versions over 3.0 use an Adeos kernel patch, slightly modified in the x86 architecture case, providing additional abstraction and much lessened dependencies on the "patched" operating system. Adeos is a kernel patch comprising an Interrupt Pipeline where different operating system domains register interrupt handlers. This way, RTAI can transparently take over interrupts while leaving the processing of all others to Linux. Use of Adeos also frees RTAI from
patent
A patent is a type of intellectual property that gives its owner the legal right to exclude others from making, using, or selling an invention for a limited period of time in exchange for publishing an enabling disclosure of the invention."A ...
restrictions caused by
RTLinux
RTLinux is a hard realtime real-time operating system (RTOS) microkernel that runs the entire Linux operating system as a fully preemptive process. The hard real-time property makes it possible to control robots, data acquisition systems, man ...
project.
RTAI-XML
RTAI-XML is a server component of RTAI, implementing a service-oriented way to design and develop real-time (RT) control applications.
This project was born to fulfill the needs of a university group, mainly focused to have a flexible platform for learning control systems design, allowing the students to test their programs remotely, over the Internet. Leaving the first wishful thinking and going to the real implementation gave rise to the alpha version of RTAI-XML, that showed the potential impact of the basic idea of a net separation of ''hard'' and ''soft'' real-time tasks in the programmation logic. What was necessary to assure that students could not crash the RT process, is now becoming a new RTAI paradigm.
RTAI-XML consists of a server component waiting for incoming calls on a box where a real-time process, the Target, is running (or ready to). A generic client program, the Host, can reach the server through the
TCP/IP network, using a standard protocol based on
XML
Extensible Markup Language (XML) is a markup language and file format for storing, transmitting, and reconstructing arbitrary data. It defines a set of rules for encoding documents in a format that is both human-readable and machine-readable ...
, and hence interact with the Target, in order to monitor the status of the RT process, to see the signals collected (or generated) by the system and also to fetch and change the RT parameters (for example, the gains of a
PID feedback ring). In other words, RTAI-XML provides a simple way towards
remoting of control applications, adding flexibility to the RTAI project, without losing the key features of an open and standard implementation.
The RTAI-XML section of this site presents the details of the implementation. The general architecture is revised, in order to focus the three key components, the Server, the ''Server-Target'' interface and the ''Server-Host'' communication. The Applications section contains some examples of control systems based on RTAI-XML and the References section contains hints and links for further readings on this topic.
See also
*
Xenomai
References
External links
*
Univ. di Padova - RTAI / Xenomai presentationRTAI-XML official website
{{Linux
Linux kernel
Real-time operating systems