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-   -   LINUX hard real time or bare C ? (http://www.linuxquestions.org/questions/linux-embedded-and-single-board-computer-78/linux-hard-real-time-or-bare-c-4175430544/)

elico 10-04-2012 02:53 PM

LINUX hard real time or bare C ?
 
Hi

What is "hard real time" LINUX based code
or C based code on a bare board ?

When very fast respnse is needed I guess a c
based code on a bare board comes first, rather then
LINUX based code .

Am I right

Thanks
Elico

crosstalk 10-04-2012 07:29 PM

What RTOS you should use depends strongly on the application. If you have a specific application in mind, what is it?

If this doesn't answer your question, then please restate it. I'm having trouble understanding what you're asking.

elico 10-05-2012 03:59 AM

My question is general about real time embedded coding .

When response time is critical and should be short like in case of
an industrial machine that needs to respond fast .

In such case is it better to control that machine with a bare board
programmed with C code or is it better to use a LINUX based board ?

The term HARD REAl TIME means fast response time
vs SOFT REAL TILE means long response tle LIKE an ATM machine .

Thanks
Elico

crosstalk 10-05-2012 09:24 AM

Quote:

Originally Posted by elico (Post 4797874)
My question is general about real time embedded coding .

When response time is critical and should be short like in case of
an industrial machine that needs to respond fast .

In such case is it better to control that machine with a bare board
programmed with C code or is it better to use a LINUX based board ?

Depends on the exact application. In many industrial settings, running bare-bones may be better. Additionally, if it's a life-critical safety application, Linux is pretty much out of the question. However, Linux does provide a lot in terms of drivers and software libraries that may be useful for an embedded application.

Quote:

The term HARD REAl TIME means fast response time
vs SOFT REAL TILE means long response tle LIKE an ATM machine .
The definitions I've heard are a bit different:
Hard real-time: The system has defined deadlines; missing a single deadline is considered complete system failure.
Soft real-time: Missing the occasional deadline is acceptable.

theNbomr 10-05-2012 01:26 PM

I think the OP is trying to distinguish between Linux as a realtime OS and bare-metal C programming. Neither of these are 'hard realtime', although you may achieve hard realtime performance with bare-metal C coding.
Strictly speaking, hard realtime is about guaranteed response time, and does not mean fast/high-speed. Normally, when guaranteed response times are required (not 'should be short'), it also implies some elevated performance level, and that is probably what causes people to misunderstand the meaning. Determinism is the name of the game for real-time performance. Only if you can guarantee response times can you call a system a realtime system. Bare Linux can not do this. Very often, it is true that 'real fast is as good as real time', but there is still a distinction.
--- rod

elico 10-07-2012 04:09 AM

Many thanks for you all .
Very informative answers .

Elico

onebuck 10-07-2012 09:11 AM

Moderator Response
 
@elico

You seem to be generally splattering the forum with related content. I suggest that you try to stay with one thread instead of open a new thread that is related to the same topic you have been posting queries about.

That way we can address the topic in it's entirety. Questions are fine but when you segment, it can not be addressed fully as to the related content.

Please look at the following;
Quote:

FYI: I suggest that you look at 'How to Ask Questions the Smart Way' so in the future your queries provide information that will aid us in diagnosis of the problem or query.
&
FYI: Netiquette is a set of social conventions that facilitate interaction over networks, ranging from Usenet and mailing lists to blogs and forums.

elico 10-09-2012 01:44 AM

Thanks
i will try .

Elico


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