What are examples of RTOS

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Hello guys, 

I think we use the real-time system only when we have to do multi task within a certain time. I think the ATM machine is a real-time system because it also works for a certain time. The time to enter the password is also fixed. If you do not enter the password within a certain time then the process starts from beginning  If you do not take money for a certain amount of time then money goes back into machine. Is ATM machine work on RTOS ? 

 

 

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Last Edited: Sun. Apr 26, 2020 - 01:55 PM
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The ones I’ve seen run Windows XP. Clearly not an RTOS.
why do you keep posting strange questions under different usernames?

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Kartman wrote:
why do you keep posting strange questions under different usernames?
I agree this is VERY suspicious behaviour. Please pick ONE account from rahulk7, ansh11, sky33, etc and stick to it or I'm simply going to block them all as this looks suspiciously like trolling to me.

 

Moderator

 

(PS I shall be watching out for accounts using the ISP "Reliance Jio Infocomm "!)

Last Edited: Thu. Apr 23, 2020 - 12:14 PM
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rahulk7 wrote:
we use the real-time system only when we have to do multi task

No.

 

"Real time" and "multi task" are entirely separate things:

  • A realtime system may be single or multitask
  • A multitask system may or may not be realtime

 

rahulk7 wrote:
I think the ATM machine is a real-time system because it also works for a certain time

That's not the usual definition of real time.

 

An ATM is just a user interaction terminal - there are no critical timings or deadline.

 

I guess an old-time mainframe computer person might have said it's "real time" as opposed to "batch" - but that's a different context.

 

As Kartman says, things like this are generally using standard operating systems like Windows - not "real time" at all.

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clawson wrote:
rahulk7, ansh11, sky33, etc 

 

muke12 is another

 

This one from  fl4r3 seems to be in the same vein:  https://www.avrfreaks.net/forum/determine-model-microprocessor-only-using-hexbin-file

 

frown

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There has been some misunderstanding, personally I don't know other users. I have gone through their profiles. They have different background. My all question's are related to free RTOS. I have the hands on experience with AVR Micro. I am proficient with C programming language. I am familiar with protocols  UART, I2C, SPI  

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What has FreeRTOS got to do with ATMs? Do you really think any bank developing/operating something as secure as an ATM would be doing so with some homebrew, open source OS?

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clawson wrote:
What has FreeRTOS got to do with ATMs? Do you really think any bank developing/operating something as secure as an ATM would be doing so with some homebrew, open source OS?

I don't have knowledge on FreeRTOS. my original question has been answered  if there is permission to continuous this thread I would like to discuses some other doubts    I just gave one example I though ATM machine run RTOS program. I have a other examples I am not sure but I think they may be examples of RTOS system.

 

 

 

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rahulk7 wrote:
I though ATM machine run RTOS program.

As pointed out, your reasoning was wrong.

 

So perhaps first you should spend some time reading-up on what really constitutes a real time system?

 

It is well documented!

 

https://en.wikipedia.org/wiki/Real-time_computing

 

https://en.wikipedia.org/wiki/Real-time_operating_system

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rahulk7 wrote:
My all question's are related to free RTOS

And yet you keep posting them all on this forum - which has nothing to do with FreeRTOS !

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clawson wrote:

I agree this is VERY suspicious behaviour. Please pick ONE account from rahulk7, ansh11, sky33, etc and stick to it or I'm simply going to block them all as this looks suspiciously like trolling to me.

+1

 

rahulk7 wrote:
They have different background. My all question's are related to free RTOS.

And one of the other profiles has asked about FreeRTOS as well.  All the other users are on the same ISP and similar subnets.

 

 

rahulk7 wrote:
I don't have knowledge on FreeRTOS.

And as it has been typed:

awneil wrote:
And yet you keep posting them all on this forum - which has nothing to do with FreeRTOS !

 

a simple google search of "FreeRTOS Community" yields tremendous results such as:

 

https://forums.freertos.org/

 

I am going to be nice and simply SUGGEST you ask your questions there and STOP asking here.

 

Jim

I would rather attempt something great and fail, than attempt nothing and succeed - Fortune Cookie

 

"The critical shortage here is not stuff, but time." - Johan Ekdahl

 

"Step N is required before you can do step N+1!" - ka7ehk

 

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Atmel Studio6.2/AS7, DipTrace, Quartus, MPLAB, RSLogix user

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 I just gave one example I though ATM machine run RTOS 

 If you quickly type in 21325449238 the ATM will give you all the money you want.

When in the dark remember-the future looks brighter than ever.   I look forward to being able to predict the future!

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Anyone read "The Daily WTF" ?

Here's a cracker: https://thedailywtf.com/articles/normal-0-false-false-errord-false-en-us (scroll down to the picture of the Barclays ATM).

 

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Here you go:

 

 

This was on the Stansted airport shuttle thingy:

 

 

EDIT

 

typo

 

 

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Last Edited: Thu. Apr 23, 2020 - 11:19 PM
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I've been on a long haul flight where they had to "reboot the inflight entertainment system" to then see a whole load of Linux startup messages scroll past on the screen in the back of the next seat.

 

What I didn't wholly understand is that like Smartphones, Android TVs and Sky+ boxes it is quite possible to make a Linux with a "quiet" startup by not enabling the console. So I did kind of wonder why the system designers would have left this exposed.

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clawson wrote:
So I did kind of wonder why the system designers would have left this exposed.

Because they were "desktop" people - not "embedded" people ... ?

 

frown

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awneil wrote:
- not "embedded" people ... ?
"Not embedded people" designing the embedded entertainment system for a Boeing?

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As everyone said this forum is not suitable for the RTOS questions. I thought at some point in your long career, you must have had a chance to work on RTOS. So I asked some question. 

 

I am curious to know if anyone has really worked on RTOS. or someone who was involved in RTOS a project. If you had worked on a RTOS project, can you tell me why did you selected only RTOS for Project ?

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I have worked on embedded projects with both RTOS and also (not so RT)OS - the latter being "Linux".

 

For example for a digital satellite TV receiver/recorder we used Nucleus Plus  https://www.mentor.com/embedded-software/nucleus/ . In that we had a little over 100 tasks with about 30 different priority levels. There was about 4MB of code for the NEC MIPS R4300 RISC processor.

 

But the point is that this message board is about AVR microcontrollers. As you would almost never choose to use an RTOS for simple code (maybe up to something like a 32KB..64KB limit?) then you won't find too much discussion of RTOS here. Of course there are a few 256KB and even 384KB AVRs and unless the majority of their flash is just occupied with data items then if there really is 128..256..384KB of code then it probably is so complex that an RTOS is justified (even though it wastes CPU time and will tend to eat system resource like SRAM).

Last Edited: Fri. Apr 24, 2020 - 09:58 AM
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rahulk7 wrote:
I thought at some point in your long career, you must have had a chance to work on RTOS. So I asked some question. 

But the questions you asked were very specifically about the particular internal details of FreeRTOS - they were not general RTOS questions!

 

For any product, the place to get specific support is to go to the specific support places. That should be obvious.

 

It has been said in your other threads, and clawson just said it again: almost nothing that's suitable to do on an (8-bit) AVR is going to benefit much (if at all) from an RTOS - so, even more so, this is a particularly poor choice of forum for your questions!

 

EDIT

 

StackOverflow would probably be a better place to ask your general questions; eg,

 

https://stackoverflow.com/questions/3611322/why-would-i-consider-using-an-rtos-for-my-embedded-project

 

But note that they are very hot on questions that have already been done to death - so be sure to search thoroughly first!

 

 

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Last Edited: Fri. Apr 24, 2020 - 10:26 AM
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I've used Arduino as a RTOS for a retro encabulator and found it extremely cromulent. That's not to embiggen my efforts.

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Kartman wrote:
I've used Arduino as a RTOS for a retro encabulator and found it extremely cromulent. That's not to embiggen my efforts.
I wonder what about this post immediately put this into my mind?...

 

 

(you probably have to be of a "certain age" to appreciate this!)

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clawson wrote:
you probably have to be of a "certain age" to appreciate this!

Oh, yes!

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Did you manage to synchronise the cardinal grammeters ?

 

https://www.youtube.com/watch?v=Ac7G7xOG2Ag

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It is always good to help others that you are doing That's why your advice's and opinion matter to me

 

awneil wrote:
But the questions you asked were very specifically about the particular internal details of FreeRTOS - they were not general RTOS questions!

 

For any product, the place to get specific support is to go to the specific support places. That should be obvious.

 

I am totally agree with you I admit that I started wrongly. I started with  programming directly which was bad start. I realized it later I am aware of the fact that we all make mistakes. We all learn from our mistakes That's why I paid more attention to understanding the need of rtos. The only question in my mind was why should I use rtos only?  I found on Google,  we use it when we need a guaranteed response, in critical time. I have used the ATM and we have to press a button within time limits, so I thought it might be an example of a rtos 

 

I have another example, a system to detect number plate of running car in toll plaza, Could this be an example of rtos?  

 

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rahulk7 wrote:

I have another example, a system to detect number plate of running car in toll plaza, Could this be an example of rtos?  

 

 

Probably not. It is probably running Linux for the image recognition.

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Haven't you already answered your own question ?

rahulk7 wrote:
I found on Google,  we use it when we need a guaranteed response, in critical time

 

By critical we mean sub-millisecond, where is the critical timing involved in reading the number plate of moving cars ?

 

I think I've sussed your confusion.

With a previous employer we started a project using ThreadX (BTW: we switched to Linux midway through and never looked back). I was going to direct you to the ThreadX website; but OMG it's become Microsoft owned; and also royalty free. WTF ?)

 

Anyway reading some of the ThreadX docs, they bang on about why you need an RTOS but illustrate that point with 95% of features that are also offered by a plain non-real-time hosted operating system like linux or windows.

 

So in your examples: The ATM and Number Plate Reader; Without doubt they will use an Operating System (OS) but not necessarily an RTOS.

 

Tight, deterministic timing is probably the only reason you would choose RTOS over plain OS.

 

BTW: Do read that stackoverflow question, linked in #20; the top answer has lots of good information and extensive links.

 

Last Edited: Fri. Apr 24, 2020 - 11:59 AM
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rahulk7 wrote:
We all learn from our mistakes

But you just stubbornly refused to learn from your mistake - and just kept on posting the off-topic questions!

 

frown

 

 we use [an RTOS] when we need a guaranteed response, in critical time. 

Your still confusing "real time" with the need for an RTOS!

 

We covered this in #4 - which you have even marked as the solution to your question!

 

Not all real time systems require an Operating System

 

I have used the ATM and we have to press a button within time limits, so I thought it might be an example of a rtos 

Again, that was covered in #4

 

 

I have another example, a system to detect number plate of running car in toll plaza, Could this be an example of rtos?  

Yes, that's a real time system - with very tight timing demands!

 

It would probably also use an RTOS

 

In fact, there's probably a realtime part - to manage the camera, image capture, etc - and a "business system" part.

 

Each would have their own OS

 

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N.Winterbottom wrote:
where is the critical timing involved in reading the number plate of moving cars

actually, it is quite critical for moving cars - because you don't get many frames to use as the car passes the camera

 

these things use some pretty high-end processors, FPGAs, etc.

 

I very much doubt they'll be using FreeRTOS, though - probably something more like VX-Works ...

 

But, as I said earlier, there's probably a separate "business system" or "back office" part - which  is not really "real time"; probably runs on linux or suchlike ...

 

 

EDIT

 

For a toll booth, the timing may not be critical - as the vehicles will have to be moving slowly.

 

But for things like ANPR for speed limit enforcement, it is a real issue!

 

Possibly also for tolling applications without toll booths ...

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Last Edited: Fri. Apr 24, 2020 - 12:14 PM
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awneil wrote:

But for things like ANPR for speed limit enforcement, it is a real issue!

OK So I'm driving my Porsche flat out through the speed trap and the "fire the flash" signal is 10ms late:

(155 mile / hour) * 10 milli second = 0.692912 meter

Does that really matter ?

 

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clawson wrote:
What has FreeRTOS got to do with ATMs? Do you really think any bank developing/operating something as secure as an ATM would be doing so with some homebrew, open source OS?

To be honest, I'm always surprised to find they're running Windows. Nothing is more confidence-shattering than seeing a blue screen Windows machine at an airport, for example.

Four legs good, two legs bad, three legs stable.

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John_A_Brown wrote:

'm always surprised to find they're running Windows. Nothing is more confidence-shattering

It's a testament to the golfing skills of the Microsoft marketing director who managed to persuade bank/airline/(insert other) chief exec to base h/w they use on M$ software. A solid strike on the 9th hole probably !

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but the system needs to capture the image, do the ANPR, do the speed measurement, etc ...

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https://www.youtube.com/watch?v=Ajxs6_V8KJM

 

I watched video, I think RTOS may be used in this project for high speed application. camera response should come within a certain time. If the camera does not give the result within the time limit then the problem can occur.

 

What is your opinion? Will RTOS be suitable ?  

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camera response should come within a certain time. If the camera does not give the result within the time limit then the problem can occur. ​​​​​​ 

The camera takes the time it needs...An RTOS won't access the results any faster than it can provide results.    The line itself is not "high speed"...it's boxes moving along.    That's not to say an RTOS could not be used, but perhaps not absolutely necessary.    Is it PC based, or controlled by a little box with a mega32 in it?...Or more likely by a PLC  system.

When in the dark remember-the future looks brighter than ever.   I look forward to being able to predict the future!

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For example Airbag control system in a car. If we drive a car at a high speed accidents may happen, in such case airbag opens and saves our life

 

RTOS can give an accurate output at right time. What do you think , Is RTOS needed ?

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Most likely not. Car ECUs tend to use a superloop.

 

Airbag response in relation to the speed of the average microprocessor is slow. As is the deployment of the airbag - measured in milliseconds. 

Apart from detecting deceleration past a certain point, what else does the airbag controller have to do? Very little. It probably spends most of its time doing self checks.

 

 

 

 

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I gave four examples that I thought could be RTOS, If there is no objection, and no one feels that I have not spent my time in finding answers to questions, then someone can tell their example for RTOS ? This will help me that your example is RTOS and why mine examples are not RTOS.

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Wasn't RTOS one of the 3 musketeers?

John Samperi

Ampertronics Pty. Ltd.

www.ampertronics.com.au

* Electronic Design * Custom Products * Contract Assembly

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Maybe a broadcast studio video control system...lots of data a being pushed around, and lots of time-critical bulk events occurring.

How about an airport radar system?   Perhaps an aircraft flight control system....lots of sensors and inputs and data streams vying for real-time attention.

I usually think of RTOS for "big processing" (microcontroller on steroids)..it certainly does not have to be limited to those cases.

 

Also RTOS can arrive on the scene when implementing complex tasks like linking to cloud based resources, or developing smart mesh networks and the like. 

 

you might like this:

http://www.ti.com/lit/wp/spry238/spry238.pdf?ts=1587792804289

 

 

 

When in the dark remember-the future looks brighter than ever.   I look forward to being able to predict the future!

Last Edited: Sat. Apr 25, 2020 - 05:49 AM
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avrcandies wrote:
A realtime system may be single or multitask
 

 

avrcandies wrote:
Perhaps an aircraft flight control system....lots of sensors and inputs and data streams vying for real-time attention.

I usually think of RTOS for "big processing"

Thanks Yes this can be an example but it would be multitasking system.  Can you imagine what would the example of real time system for single task? I am looking for long time on the Internet, I have not found success yet. Maybe my Google search technique is very bad

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You don't seem to have a good idea of what a RTOS is, let alone how to use one or even how to write one. The ESP32 framework is built on freeRTOS. Why a RTOS? Does it actually need a RTOS, or did they just use freeRTOS because it was free and well supported? When you can answer those questions yourself, then you will have a better grasp of the concept. Since you and your friends are experienced in C coding along with uart, spi and i2c, this should be a straightforward task.

 

 

Why would you need a RTOS for a single task? That totally negates the need for one.

 

 

Last Edited: Sat. Apr 25, 2020 - 06:07 AM
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Kartman wrote:

Why would you need a RTOS for a single task? That totally negates the need for one.

 

I fully agree with you But as previously told that  realtime system may be single or multitask, I was just thinking what could be example for single task. May be awniel can tell clearly.  

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a realtime system is just a description for a system that has hard time constraints. Being 'realtime' doesn't mandate a RTOS.

As I mentioned, early car ecu's didn't have an OS - they used a superloop. What's a 'superloop' - you can Google that one. Nevertheless, the code was a single thread that ensured all tasks were completed within the required time by design.

 

Have you Googled avrfreaks kartman multitask?

You should find a tutorial I wrote many years ago.

 

Still - can you adequately answer what a RTOS is, what it does and how does it work?

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Maybe my Google search technique is very bad

Practice makes perfect.  Why do you worry so much about RTOS?  Remember, you can rearrange it as SORT.  SORT methods are also covered extensively in many programming languages & worth a study. 

When in the dark remember-the future looks brighter than ever.   I look forward to being able to predict the future!

Last Edited: Sat. Apr 25, 2020 - 08:21 AM
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avrcandies wrote:
Why do you worry so much about RTOS?  

Indeed!

 

You keep going on as if an RTOS were an essential part of any & all real time systems - it is not!

 

Example:

In #36,rahulk7 wrote:
RTOS can give an accurate output at right time.

No, it does not "give" that - you can do that without any operating system at all

 

Again, not all real-time systems need any operating system at all.

 

But if you do use an OS in your real time system, then it must be a real time OS !

 

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There is no such thing as a 'Real Time' system. Especially when using an 'RTOS' (whatever that might mean). The 'R' in RTOS ought to mean 'Right' as in 'now is the right time to run this task'.

 

Any small system, especially if running on a chip like an AVR, will be slower if using an RTOS than a similar system using interrupts and a while(1) loop. An RTOS has overheads.

 

A better acronym might be JITOS, as in Just In Time Operating System.

 

In fact, I have issues with the 'OS' bit as well because many RTOSes aren't an OS at all but are merely task switchers, or context switchers if you will.

 

So, instead of RTOS it should be JITTS (Just In Time Task Switcher).

 

*note, since we're on AVRfreaks I'm aiming most (all?) of my comments on systems running on AVRs and similar controllers.

#1 Hardware Problem? https://www.avrfreaks.net/forum/...

#2 Hardware Problem? Read AVR042.

#3 All grounds are not created equal

#4 Have you proved your chip is running at xxMHz?

#5 "If you think you need floating point to solve the problem then you don't understand the problem. If you really do need floating point then you have a problem you do not understand."

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This reminds me of recent interview - you visit the headhunter and they use keywords like 'RTOS','C++','ARM' etc, but they really don't know what they mean. The employer has used these terms and that's what the headhunter asks. My usual answer is along the lines of 'yes, extensively'. I then target my resume to use these terms. Only when you get to the interview do you find out what the employer really wants.

 

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Kartman wrote:

can you adequately answer what a RTOS is, what it does and how does it work?

 

I am not fully aware of this, so I have asked the question here. I spent all my time on research and whatever I understood, I explained here.

 

RTOS is system that react to input within specific time limit. It has to guarantee that it will respond within some time limit

 

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avrcandies wrote:
 Why do you worry so much about RTOS?  

Having knowledge of RTOS is plus point in the embedded world. It has more demand in Embedded world.  It would be good for me if I get hands on experience with RTOS. I am doing my best. remember I am just looking help to understand RTOS I am not asking a complete program my first attempt is to understand fundamental first  

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You asked for examples of RTOS, but it is clear you don't really know what a RTOS is. You have read my tutorial? Seems not by your response.

 

A RTOS usually consists of a number of things:

1. the means to swap tasks - this may be co-operatively or pre-emptively

2. it has to schedule what task should run at a given point in time

3. the scheduling algorithm is what defines the R in RTOS. In Windows or Linux, the scheduler is more interested in getting the work done whereas in a RTOS it is more concerned with ensuring certain tasks complete by the required time. Exactly what this time is varies. It could be nanoseconds but more commonly microseconds or milliseconds.

4. functions to support inter-process communication - semaphores, mutexes, queues etc. Again, these are not specific to a RTOS. You'll find these in Linux and Windows as well.

5. Timers to time the running of tasks.

 

Read up on freeRTOS - does it have these features?

How about ThreadX, NUTTX, RTEMS, ChibiOS and so on?

What are common features you have noted?

 

In reality, a RTOS is not that much different than managing a number of labourers to dig a hole. Having more than one labourer dig a 2ft hole is probably not going to work, but the dirt needs to be taken away. But the dirt can't be moved until it is dug up.

So we have two tasks - one digging the hole, the other moving the dirt - they are both related to each other. The RTOS manages the interaction.

 

 

 

 

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