Small footprint RTOS for embedded system

What is your target micro?

Google is your friend.

--
Michael N. Moran           (h) 770 516 7918
5009 Old Field Ct.         (c) 678 521 5460
Kennesaw, GA, USA 30144    http://mnmoran.org

"So often times it happens, that we live our lives in chains
  and we never even know we have the key."
"Already Gone" by Jack Tempchin (recorded by The Eagles)

The Beatles were wrong: 1 & 1 & 1 is 1

Do it yourself. Developing such RTOS is a task for one day.

I also know a lot of smart words and phrases: innovation, surge, it is what it is, java dot net, misunderestimate, strategic focus, memory leakage, priority inversion, neural network, quality management.

Vladimir Vassilevsky DSP and Mixed Signal Design Consultant

And they say sarcasm doesn't come across on USNET..

;-)

Best regards, Spehro Pefhany

--
"it's the network..."                          "The Journey is the reward"
speff@interlog.com             Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog  Info for designers:  http://www.speff.com

If you want to roll your own rtos, try to get your hands on Ric Holt, et al's, books:

pt

Search your local amazon.com for books by "labrosse", and you'll find Jean J. Labrosse's "MicroC OS II: The Real Time Kernel (With CD-ROM)", ISBN 978-1578201037. It's a classic little RTOS that has been around for years, and comes with tutorials on RTOS's and how to use them.

Here's a paper that describes its implementation in a minature remote- controlled helicopter:

s/214B.pdf =2E

Googling on "ucOS" and/or "labrosse" will find more.

Not free by any definition!

..and cleaning up after such a mess is a career for life.

--Gene

SteveM ?µÀ:

I use "samllRTOS" to meet our product requirement. It's simple and small and free. You can run it on 8051 with 4kb code memory and 128RAM. But I only have Chinese reference for "smallRTOS". If you are interested in it and couldn't get it from google, email me to send a copy of source code to you. (This RTOS is created by member of Philips China, so maybe not more English reference can be found on internet easily.)

Best wishes,

Min

small

Try

and Both offe "free" use to educate yourself about small footprint RTOS issues. Bot offer very reasonable license fees to build commercial products.

There's also

The book is not free, the RTOS is free for educational purposes, albeit not commerial use. It can be downloaded at

At the commercial price it is very close to free unless you think you can duplicate it in under a week (see VLV in this thread).

Scott

It appears to be several thousand dollars *per product*, i.e. you have to pay again for each project you use it on. While this may still be value for money (I don't know), I don't think it can be described as "very close to free".

Especially since there *are* totally, actually free alternatives (and this was what the OP asked for).

--

John Devereux

The OP question was about basic task switch with semaphores. This is not a big deal; one can develop it himself. If you are familiar with the CPU, then it takes about a day. I've done that many times; works fine for the small projects. You can also see the SST for example. However a real full blown commercial RTOS should include much more then just task switch and semaphores. There should be messaging, trace/debug facility, memory management, hardware abstraction and a large set of useful utilities and drivers such as file systems, protocol stacks and GUI. Of course, it is a big work to develop all of that. Being disappointed with mucos, I developed somewhat more advanced small RTOS of my own. Of course, it was rewritten several times and it took a while to develop; it works fine now. The best output of it was the understanding of what is really required and why the certain things should be done by certain ways. However for the bigger projects I would consider a CPU with MMU and Windows CE as an OS.

Vladimir Vassilevsky DSP and Mixed Signal Design Consultant

If you look at the actual development costs for most embedded systems, then yes, it can be described as "very close to free".

FreeRTOS and XMK are two that come to mind:

IIRC, they both impose requirements that you offer to supply source code to your customers.

--
Grant Edwards                   grante             Yow! RELATIVES!!
                                  at               
                               visi.com

... snip ...

Are you objecting? Do you consider that excessive?

--
 Chuck F (cbfalconer at maineline dot net)
   
   Try the download section.

No.

No.

Do you find my mentioning it objectionable or excessive?

I was just pointing out that they do impose that requirement. It's one thing that has to be considered when making a choice. I have customers who would rather spend a couple thousand dollars than set up and maintain a system/procedure for distributing source code to customers all over the world.

--
Grant Edwards                   grante             Yow!  Of course, you
                                  at               UNDERSTAND about the PLAIDS
                               visi.com            in the SPIN CYCLE --

FreeRTOS requires that any changes to the RTOS functions must be supplied to customers, and that the FreeRTOS code (not the application). There is no such requirement as to application code linked to the RTOS. See

"Linking FreeRTOS statically or dynamically with other modules is making a combined work based on FreeRTOS. Thus, the terms and conditions of the GNU General Public License cover the whole combination.

As a special exception, the copyright holder of FreeRTOS gives you permission to link FreeRTOS with independent modules that communicate with FreeRTOS solely through the FreeRTOS API interface, regardless of the license terms of these independent modules, and to copy and distribute the resulting combined work under terms of your choice, provided that

1. Every copy of the combined work is accompanied by a written statement that details to the recipient the version of FreeRTOS used and an offer by yourself to provide the FreeRTOS source code should the recipient request it. 2. The combined work is not itself an RTOS, scheduler, kernel or related product. 3. The combined work is not itself a library intended for linking into other software applications."

Check out MiniRTL. :):)

Karthik Balaguru

Right. I didn't mean to imply that the user's application source code had to be distributed -- I apologize is that's what it sounded like. But, distributing FreeRTOS source code imposes a cost on the user that has to be considered just as one would the licensing cost of a "non-free" RTOS that doesn't require the user to distribute any source code to the user's customers.

--
Grant Edwards                   grante             Yow! I had pancake makeup
                                  at               for brunch!
                               visi.com

You don't specify your target?

You'll find a very simple "sEOS" scheduler for LPC2xxx microcontrollers here:

(along with some half-finished documentation in Chapter 4).

Michael.