Re: [gentoo-embedded] Hard Real Time Systems with Gentoo?

[Bob Paddock]

On Saturday 13 January 2007 08:10, wireless wrote:
> Bob Paddock wrote:
> > Does anyone know of any Hard Real Time Systems,
> > where deterministic response is required, that work
> > with Gentoo-Embedded?

> Um, the way you posed your question, is sure to solicit
> 'religious wars' on a few issues.

The way I posed the question was meant to result in:

"Yes, there is a RTOS that works well with Gentoo-Embedded,
and it is XYZ at http...."

How would you have asked the question?

https://www.rtai.org/ is one of the many Linux RTOS
extensions out there.  Any of them work with Gentoo?
I like Gentoo, and simply wanted to use it in a project
I have coming up, but it has 'hard' time requirements.

http://www.rtnet.org/ comes to mind, as well for the networking
aspect of things.   A Time Triggered Protocol.

> Soft real time, means that timing constraints are soft
> or guildlines for process performance metrics.

Erlang is a 'Soft' Real Time System, not what I need at the moment.

> Hard real time, means the timing constraints are hard
> or an absolute requirement.

I am aware of the issues, that is why I made the distinction,
in what I was after.

> to not be 'real time'. But think about if a missile,
> is suppose to change it's rudder in response to an
> AD input, in 150ns, does it mean that the missile   as
> as system is a failure if the rudder response is
> 151 ns or 150.002 ns?

If it is in the targeting system, it makes the difference between
hitting the target or not.  A 1 ns difference, is a large
area to transverse when your missile is traveling at Mach-6.
A missed target is a failed Missile System.

TechUpdate from the Missile Defense Agency
comes out quarterly.  MDA funds a lot of research in other
areas.   The Summer 2006 laying here beside me is
about "Phasing out Brest Cancer" using Microwaves.
"Fuzzy-logic software" on page ten might be more relevant to this
list.  Check it out at: http://www.mdatechnology.net/
Maybe someone can make a ebuild for their screen saver?

> Determinism is another funny character. Real embedded
> systems use a 'state machine' design where every
> state or transition is fully characterized and defined.
>
> ON a large complex system, it is virtually impossible to
> discover, characterize, define and test all possible states
> of a complex system.

Use the appropriate tools and languages such as Esterel.
http://www.esterel-technologies.com/

or

http://www.tttech.com/ .

> (just look at the behavior of a single
> female of any given species).

Does that fit my requirement of being Deterministic?  :-)

> Biological systems are but
> one example of a system that cannot be fully characterized
> due to many factors but genetic modification being one
> example.

Nor am I building a Biological Entity, at the moment at least.
If you want to give that a shot take a look here:
http://www.rexresearch.com/crosse/crosse.htm 

> Embedded linux anything, currently, can never be fully deterministic.

Embedded Linux can be run as a task of a fully deterministic RTOS,
built with a Finite State Machine if you like.
Any done with Gentoo-Embedded?

> Using languages such as C++ or more reaching OO languages, only
> exasperates the goal of being fully deterministic. In stead of
> the educators realizing and admitting that very few things
> actually need HRT and virtually nothing complex that we build,

I know what I'm building, as well as being well aware of the high
importance of System Design Requirements.

> <flames on>  Obviously, you'll find lots of vendors and educated
> folks ...

But will I find one that actually answered my question?  :-)

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