rtos features

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hello,

i am evaluating various rtos for on of our products based on arm7. i
have been looking at Nucleus, embOS, Rtxc, Threadx and MicroC os-ii.
Of the lot Threadx and embOS seem to be good. Although i believe that
the others are just as good. It seems hard to zero in one choice. I
have been searching for reviews in the newsgroups. I have found some
scattered info for nucleus and threadx (threadx apparently seems to be
better).

I am primarily looking at these features:
Scheduling, events, queues, low interrupt latencies, small mem
footprint, fast context switching, ....

I would appreciate if somebody could post their views/experiences on
these rtos'.


Thank you
Sagar

Re: rtos features

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You maybe should consider Sciopta as well :-) 100% Assembly.
Designed for low-mem to high-speed applications.
--
42Bastian
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Re: rtos features
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I have direct experience with ThreadX (in a source level license) and found
it to be solid, well debugged, and the support to be outstanding. It has
been excellent to us (we've shipped about 30 products with it).

-->Neil



Re: rtos features
Did you consider VxWorks? VxWorks has been around for a long time and
is quite stable.

Sandeep
--
http://www.EventHelix.com/EventStudio
EventStudio 2.0 - Real-time and Embedded System Design CASE Tool

Re: rtos features
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You should take a look at CMX-RTX from CMX Systems ( http://www.cmx.com ) also.
CMX-RTX has all the features you are looking for and no royalties! CMX-RTX runs
on the ARM7 and about 30 other microprocessors including DSPs.

Paul Bosselaers

Re: rtos features
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I  am very partial to MicroC/OS-II.  It offers all the features you list
including fast context switching.  It has been ported to all kinds of chips
based on ARM7 and ARM9 cores and the ports are available freely from
Micrium's web site.  Jean Labrosse published a book on the OS (available on
their web site or from Amazon) and the book includes a CD with all of the
source code.  You can have it all for about US$70.  A production license is
under $3000.

MicroC/OS-II has also been tested extensively for use in safety critical
systems.

--
Scott
ExoTech R&D, Inc.




Re: rtos features

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chips
on
is

When you say a production license is under $3000, what sort of quantities is
that for?  Do they make a distinction between a product with, say, 50 units
a year, and one with several thousand?  And do you need a seperate license
for different products (or different versions of the same product)?




Re: rtos features
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The license is $2750 for a unlimited number of copies for a single product.
Contact Jean Labrosse at Micrium for details.



Re: rtos features

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Sadly it's too expensive for me, I'll have to stick to ecos! I do a lot
of small quantity products, and while I suppose I could argue that all
my products are just variants, I can't afford to get into an argument,
so that's that.

Paul Burke



Re: rtos features
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    What about Real-Time Linux?  There's a free version available that I've
used for years in pseudo PCs but they also have versions for a variety of
uPs.

    Norm


Re: rtos features
Thanks guys for the feedback. I should have mentioned the chip specs
earlier:
it is an arm7tdmi-s with: 512 KB program flash, 32KB data flash, 32 KB
ram.

with these tiny resources, I am begining to feel that embOS
(www.segger.com) may be my choice. All other RTOSes that i had
mentioned before seemed to occupy too much space in flash or they
needed more resources in RAM.

for eg: for the features that i mentioned before, embos requires:
kernel space in flash: 6.4 KB
kernel ram usage: 51 bytes
ram per task: 32 bytes

the only apparent negative aspect to it compared with other RTOSes
like threadx seems to be the context switch time(18us vs 1.9us of
threadx) and interrupt latency (max 6us vs 1.8us of threadx). but
threadx uses more ram per task. maybe threadx stores a lot of process
info in ram and hence has to save less while switching.

Regards
Sagar

snipped-for-privacy@yahoo.com (Sagar) wrote in message
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Re: rtos features

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I doubt that these figure are true. It may represent the bare OS
without message-queues and semaphores or whatever.

Sciopta e.g. needs with full functionality 15KB flash and about 2K of
kernel-ram. 128Bytes per task.
_But_ this includes already timeout-servers, message-queues.

Ask them to give the maximum numbers.

BTW: We have Sciopta+webserver+tcp/ip+PPP running in 512K Flash/64K
RAM on a Coldfire 5282.
--
42Bastian
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Re: rtos features
On Wed, 23 Jun 2004 05:24:33 GMT, snipped-for-privacy@yahoo.com (42Bastian

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Apart for the low per task RAM for a modern processor with multiple
registers, those figures looks quite reasonable.

Essentially in a small RT kernel, you need a per task stack (in
addition to the stack needed for the actual task execution with return
addresses and HLL variable storage) that is capable of storing the
task context, which at least consists of the processor registers.
_If_ a message queue is used, some pointers to the actual message
blocks.

In the days of 8 bit processors, there were a lot of company specific
RT kernels requiring 2-4 KiBytes. With a 6809 kernel I once worked
with, in addition to the per task stacks only has 3 bytes of kernel
RAM per task, two bytes containing the saved stack pointer for not
currently running tasks and a third byte to hold some task state
information bits :-).

Paul
    

Re: rtos features
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I just wonder, why they give an odd number for the kernel-ram usage.
It seems to me that these are maybe 8bit/16bit figures.

Also, I think they don't count the registers for the per-task RAM.

This normaly include task-state, time-out values, stack-pointer etc..

--
42Bastian
Do not email to snipped-for-privacy@yahoo.com, it's a spam-only account :-)
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Re: rtos features
hello,

we got some good numbers from cmx-rtx as well. it seems to be faster
than embos and also doesnt seem to use as much ram as other rtoses.

cmx interrupt latency: 1.375us
context switch time: 3.175us

kernel ram usage: 180 to 200 bytes.

anybody have any good experiences with cmx-rtx. what kind of timer
funcitionality  do they support.

Regards
Sagar


snipped-for-privacy@yahoo.com (Sagar) wrote in message
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Re: rtos features
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At what CPU clock ? 1MHz, 10MHz, 100MHz ?

I'd not go for pure context switch-time, rather for a IPC sequence.

--
42Bastian
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Re: rtos features
the clock speed is 40 mhz. i compared these latency figures with other
rtoses running at the same clock speed.

Sagar

snipped-for-privacy@yahoo.com (42Bastian Schick) wrote in message
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Re: rtos features
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We really made good experience with the Segger Tools (embOS/emWin). We
used it on a different CPU but will need an ARM chip for a new
application for which we will choose their system again. It inlcudes a
start project and the viewer (included) is very helpful. The best way
to find out if it is suitable for your application is to download the
trial version. Just go to www.segger.com/download.html.

Mike

Re: rtos features
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We really made good experience with the Segger Tools (embOS/emWin). We
used it on a different CPU but will need an ARM chip for a new
application for which we will choose their system again. It inlcudes a
start project and the viewer (included) is very helpful. The best way
to find out if it is suitable for your application is to download the
trial version. Just go to www.segger.com/download.html.

Mike

Re: rtos features
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I've worked with Nucleus PLUS on a number of Intel and Motorola
platforms since it came out around 10 years ago.  I've been
very satisfied with it.  I particularly like the dual-level
interrupt system that permits the use of asynchronous procedure
calls to process high-priority events with interrupts enabled.

Advantages are a source license with no royalties, ala carte
selection of only the synchronization primitives you want,
portability of code, and good coverage of many processor
families, particularly ARM.

Disadvantages are that the license is getting a bit pricey
and is for one product.  Use of resources is more than some
of the tighter, less general systems.

Tom Taylor

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