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Re: I don't use an RTOS because...
On Sat, 15 Jan 2005 15:22:26 -0500, "Michael N. Moran"

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A long time ago my group was developing multitasking applications on
PDP-11 under RSX-11. Most people had good experience in designing and
writing batch and interactive time share applications. After teaching
them about multiple tasks and some of the most important OS
mechanisms, it took several months until they independently could
split the applications into tasks and design the synchronisation and
communication between them. Even after that, you had to check their
code for stupid things, such as busy loops (as a heritage of their
batch and timesharing days).

Paul
 

Re: I don't use an RTOS because...
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This sub-thread is contrasting rolling your own code
scheduler and writing your own libc versus using an
existing RTOS, and whether or not the RTOS is to be
trusted.

My experience is that at the core RTOS API's are the
same and that the structure of a pre-emptive RTOS kernel
is simple enough to be as reliable (perhaps more so) than
most large libraries such as libc.

As for having a team of inexperienced software engineers
working on a project for which they are not qualified
... that's another issue ;-)

--
Michael N. Moran           (h) 770 516 7918
5009 Old Field Ct.         (c) 678 521 5460
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Re: I don't use an RTOS because...

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99.999% of C library functions are irrelevant for small embedded systems so
what's to write?

Ian
--
Ian Bell

Re: I don't use an RTOS because...

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Agreed.

I very occasionally use sprintf if there is an LCD but
otherwise can't think of anything.

Mike Harding


Re: I don't use an RTOS because...
On Sat, 15 Jan 2005 08:32:01 +1100, Mike Harding

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[...]
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Ermmm...

strcpy?
strcmp?
strlen?
memcpy?
memset?
memcmp?
size_t?
offsetof?
ato(i|l)?
strto(l|ul)?
NULL?
assert?
ctype.h?
limits.h?
stdint.h?

sprintf is usually too large for the applications I work on.

Regards,

                               -=Dave
--
Change is inevitable, progress is not.

Re: I don't use an RTOS because...

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The above are extremely application dependent.

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There is never enough memory in a small embedded system for these to be
necessary.

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Again extremely app dependent

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This is a LIBRARY FUNCTION???

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Most definitely not.

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Nope.


Damn right it is.

Not to mention that A) most of the c library functions are so generalised
they contribute only bloat and B) it's bad enough finding bugs in you own
code without having to sort them out in the vendors Clib.

Ian

Ian
                  
--
Ian Bell

Re: I don't use an RTOS because...
On Fri, 14 Jan 2005 21:52:19 GMT, snipped-for-privacy@hotmail.com (Dave Hansen)

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Very rare that I would use any of the above.

If I want to copy memory (for example) two pointers usually do
the trick.

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It "usually" is for me too - that why I said " very occasionally"
but a number of compilers provide cut-down versions.

Mike Harding


Re: I don't use an RTOS because...
On Sat, 15 Jan 2005 14:03:14 +1100, Mike Harding

[... C Library Functions ...]

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You roll your own memcpy, but pull in sprintf for simple string
formatting?  Permit me to shake my head in amazement...

Regards,

                               -=Dave
--
Change is inevitable, progress is not.

Re: I don't use an RTOS because...
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memcpy = frequently used function, large data moves,
hand-optimization->speed optimization.

The drive for a hand-rolled sprintf is totally different; the goal
being to reduce memory footprint. If the compiler provides a cutdown
version of the function, it can make sense to use it.


Re: I don't use an RTOS because...
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Well, the moment you do 32 bit arithmetic on an 8-bitter, most likely a
library function is called...

Meindert



Re: I don't use an RTOS because...
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Yes the maths library is the most usefull part.

Re: I don't use an RTOS because...

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No,no,no,no,no not unless you absolutely *have* to do floating point
arithmetic.

Ian
--
Ian Bell

Re: I don't use an RTOS because...
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I beg to differ. The Imagecraft AVR compiler for instance produces direct
code for 8 and 16 bit operations, but calls lib routines when you use longs.

Meindert



Re: I don't use an RTOS because...

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Which is precisely why you need to think very carefully before doing so.

Ian
--
Ian Bell

Re: I don't use an RTOS because...
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As usual, the arguments come down to the "embedded system"
qualifiers. Here the qualifier is small. However, there are
*many* of us who work with embedded systems that are moderate
to quite large.

If the complexity is large, then an RTOS helps to
contain and manage that complexity, as does the
careful selection of libraries.


--
Michael N. Moran           (h) 770 516 7918
5009 Old Field Ct.         (c) 678 521 5460
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Re: I don't use an RTOS because...

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As the one who used the qualifier (deliberately) I would be inclined to use
one here and say 'an RTOS *can* help contain and manage complexity as *can*
the careful selection of libraries.

Ian (Mr. Qualifier ;-)


--
Ian Bell

Re: I don't use an RTOS because...
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And what about malloc/free ?!
It is commonly used as many discussion here show.

-

An how small is small ? Todays embedded systems range from a 6-pin PIC
up to many-megabytes telecom routers.

As for the RTOS I maintain we say all below 4K RAM is too small for
_our_ RTOS (dynamic, message passing).
--
42Bastian
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Re: I don't use an RTOS because...


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In my field we call 6-pin PICs "Supercomputers" because they
have so much more capabilities than what we use...


Re: I don't use an RTOS because...
On Mon, 17 Jan 2005 10:39:18 +0000, Guy Macon

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Out of curiosity, what are _you_ using, 1-bit serial CPUs (no joke,
they exist).

--
42Bastian
Do not email to snipped-for-privacy@yahoo.com, it's a spam-only account :-)
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Re: I don't use an RTOS because...
Reasons -
1/. Cost
2/. Size
3/. Complex of project - Do you thing toggling a lamp need a RTOS ?

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