Forums

Hard real time RTOS

Started by "M. Manca" November 28, 2012
Hi,

is there anyone using or that used in the past a hard real time OS with
LPC series of microcontrollers?
Regards,


An Engineer's Guide to the LPC2100 Series

On 28/11/2012 16:50, M. Manca wrote:
>
>
> Hi,
>
> is there anyone using or that used in the past a hard real time OS with
> LPC series of microcontrollers?
> Regards,
If I were to answer your question as literally as you have stated it I
would just say "yes", and leave it at that.

I assume however you are asking for an as yet unstated reason, so to try
and guess your next questions [I spend a lot of time on technical
support guessing things] I suggest looking at the following link for
several FreeRTOS on LPC projects:

http://www.lpcware.com/

Regards,
Richard.

+ http://www.FreeRTOS.org
Designed for microcontrollers. More than 7000 downloads per month.

+ http://www.FreeRTOS.org/trace
15 interconnected trace views. An indispensable productivity tool.
Hi
> is there anyone using or that used in the past a hard real time OS with
> LPC series of microcontrollers?

Maybe you should first define what _you_ think is a "hard real time"(*) OS.
There a plenty of RTOS around. And all of them can be named "hard real time".

So define your constraints (chip, clock, and timing) then you will get
better answers from someone who maybe had the same or similar environment.

(*) "real time" means _for me_, the reaction on an event. If your
controlling a super tanker you have minutes, if you control a small
quadro-copter maybe only a few microseconds.

--
42Bastian
+
| http://www.sciopta.com
| Fastest direct message passing kernel.
| IEC61508 certified.
+
Il 28/11/2012 18:51, 42Bastian ha scritto:
>
>
> Hi
> > is there anyone using or that used in the past a hard real time OS with
> > LPC series of microcontrollers?
>
> Maybe you should first define what _you_ think is a "hard real
> time"(*) OS.
> There a plenty of RTOS around. And all of them can be named "hard real
> time".
>
No. My definition is simple and very accurate, you can find the
difference between hard and soft RTOS in every University Course about
Calculators Systems (or similar name), in every Computer Science
dictionary and I think also with Google.

Anyway these are pretty good definitions for both:

A hard real time OS is an OS that guarantees to meet a deadline
deterministically.
A soft real time OS (usually called RTOS) usually or generally meet a
deadline.

For instance the deadline is that you need that a specific task to be
executed every 100 ms and it has to complete in less then 2ms.
An RTOS that deterministically assure these 2 deadline constraints is a
hard RTOS, if it can usually or generally meet these 2 constraints it is
a soft RTOS. So the difference is in the assurance not who is the
speedest one.

So, now I thin it is clear what I am searching for.
> So define your constraints (chip, clock, and timing) then you will get
> better answers from someone who maybe had the same or similar environment.
>
> (*) "real time" means _for me_, the reaction on an event. If your
> controlling a super tanker you have minutes, if you control a small
> quadro-copter maybe only a few microseconds.
>
> --
> 42Bastian
> +
> | http://www.sciopta.com
> | Fastest direct message passing kernel.
> | IEC61508 certified.
> +



Il 28/11/2012 18:35, FreeRTOS Info ha scritto:
>
> On 28/11/2012 16:50, M. Manca wrote:
> >
> >
> > Hi,
> >
> > is there anyone using or that used in the past a hard real time OS with
> > LPC series of microcontrollers?
> > Regards,
>
> If I were to answer your question as literally as you have stated it I
> would just say "yes", and leave it at that.
>
What hard RTOS do you use?
> I assume however you are asking for an as yet unstated reason, so to try
> and guess your next questions [I spend a lot of time on technical
> support guessing things] I suggest looking at the following link for
> several FreeRTOS on LPC projects:
>
> http://www.lpcware.com/
>
> Regards,
> Richard.
>
> + http://www.FreeRTOS.org
> Designed for microcontrollers. More than 7000 downloads per month.
>
> + http://www.FreeRTOS.org/trace
> 15 interconnected trace views. An indispensable productivity tool.



Hi

> A hard real time OS is an OS that guarantees to meet a deadline
> deterministically.
> A soft real time OS (usually called RTOS) usually or generally meet a
> deadline.

Ok. Nice definition.

> For instance the deadline is that you need that a specific task to be
> executed every 100 ms and it has to complete in less then 2ms.
> An RTOS that deterministically assure these 2 deadline constraints is a
> hard RTOS, if it can usually or generally meet these 2 constraints it is
> a soft RTOS. So the difference is in the assurance not who is the
> speedest one.
>
> So, now I thin it is clear what I am searching for.

Nope. Again. Any pre-emptive RTOS can assure such within its constraints.
And it much depends on your application for most RTOS's.

If your CPU is so slow, that it is not able to do the relevant tasks
within a certain time, it is not the fault of the RTOS.

So again, any pre-emptive RTOS (IMHO) can be called a hard one if your run
it within its constraints.

Means, you have to specify your environment first. Than you can check if a
certain RTOS can handle it.

Cheers,
--
42Bastian
+
| http://www.sciopta.com
| Fastest direct message passing kernel.
| IEC61508 certified.
+
On 28/11/2012 18:12, M. Manca wrote:
> Il 28/11/2012 18:35, FreeRTOS Info ha scritto:
>>
>> On 28/11/2012 16:50, M. Manca wrote:
>>>
>>>
>>> Hi,
>>>
>>> is there anyone using or that used in the past a hard real time OS with
>>> LPC series of microcontrollers?
>>> Regards,
>>
>> If I were to answer your question as literally as you have stated it I
>> would just say "yes", and leave it at that.
>>
> What hard RTOS do you use?

Umm. FreeRTOS? Or does that not meet your requirements as a hard real
time OS?

Are you going to continue to ask one question at a time or provide some
information that allows you to get all the information you want in one go?

Regards,
Richard.

+ http://www.FreeRTOS.org
Designed for microcontrollers. More than 7000 downloads per month.

+ http://www.FreeRTOS.org/trace
15 interconnected trace views. An indispensable productivity tool.

Il 28/11/2012 19:24, FreeRTOS Info ha scritto:
>
> On 28/11/2012 18:12, M. Manca wrote:
> >
> >
> > Il 28/11/2012 18:35, FreeRTOS Info ha scritto:
> >>
> >>
> >>
> >> On 28/11/2012 16:50, M. Manca wrote:
> >>>
> >>>
> >>> Hi,
> >>>
> >>> is there anyone using or that used in the past a hard real time OS
> with
> >>> LPC series of microcontrollers?
> >>> Regards,
> >>
> >> If I were to answer your question as literally as you have stated it I
> >> would just say "yes", and leave it at that.
> >>
> > What hard RTOS do you use?
>
> Umm. FreeRTOS? Or does that not meet your requirements as a hard real
> time OS?
>
> Are you going to continue to ask one question at a time or provide some
> information that allows you to get all the information you want in one go?
>
In my understanding FreeRTOS doesn't meet, it should be a soft RTOS
because it doesn't assure to deterministically meet deadlines.
My question is just if there is someone using a hard RTOS with LPC2xxx
or LPC1xxx families of microcontrollers, what is and why choosed that RTOS.
> Regards,
> Richard.
>
> + http://www.FreeRTOS.org
> Designed for microcontrollers. More than 7000 downloads per month.
>
> + http://www.FreeRTOS.org/trace
> 15 interconnected trace views. An indispensable productivity tool.



Il 28/11/2012 19:23, 42Bastian ha scritto:
>
>
> Hi
>
> > A hard real time OS is an OS that guarantees to meet a deadline
> > deterministically.
> > A soft real time OS (usually called RTOS) usually or generally meet a
> > deadline.
>
> Ok. Nice definition.
>
> > For instance the deadline is that you need that a specific task to be
> > executed every 100 ms and it has to complete in less then 2ms.
> > An RTOS that deterministically assure these 2 deadline constraints is a
> > hard RTOS, if it can usually or generally meet these 2 constraints it is
> > a soft RTOS. So the difference is in the assurance not who is the
> > speedest one.
> >
> > So, now I thin it is clear what I am searching for.
>
> Nope. Again. Any pre-emptive RTOS can assure such within its constraints.
> And it much depends on your application for most RTOS's.
>
No, all RTOS can't assure to meet a deadline, they normally or usually
can but not always. The main difference is how works the scheduler and
what constraint you can define for every task.
> If your CPU is so slow, that it is not able to do the relevant tasks
> within a certain time, it is not the fault of the RTOS.
>
> So again, any pre-emptive RTOS (IMHO) can be called a hard one if your run
> it within its constraints.
>
> Means, you have to specify your environment first. Than you can check if a
> certain RTOS can handle it.
>
As I said it isn't a speed problem, it is an deterministically assurance
problem.
> Cheers,
> --
> 42Bastian
> +
> | http://www.sciopta.com
> | Fastest direct message passing kernel.
> | IEC61508 certified.
> +



Hi

> In my understanding FreeRTOS doesn't meet, it should be a soft RTOS
> because it doesn't assure to deterministically meet deadlines.
> My question is just if there is someone using a hard RTOS with LPC2xxx
> or LPC1xxx families of microcontrollers, what is and why choosed that RTOS.

What you want is an RTOS with an deadline scheduler, that is one, that
modifies the priorities of tasks according their deadline (earliest
deadline first).

Most RTOSs around use a pre-emptive priority based scheduler which can be
used to mimic a DL-scheduler by the application.

Actually, I don't know of any DL-scheduler RTOS. I know OSE had one on top
of its normal scheduling some years ago.

--
42Bastian
+
| http://www.sciopta.com
| Fastest direct message passing kernel.
| IEC61508 certified.
+