Embeded Tutorial?

I'm looking for a tutorial that I can forward to some folks.  I know of 
three different ways of implementing software.  

In the first, you have just one real and virtual thread of control, and 
the software goes something like:

main()
{
  // setup
  ...
  while(1)
  {
    do_this();
    delay(a_while);
    do_that();
    delay(a_while_longer);
    do_the_other_thing();
    delay(even_more);
  }
}

In the second, you're too cheap to buy an RTOS, but you want to have 
multiple virtual threads of control, so you use what I was taught to call 
a task loop and what most folks seem to call a state machine:

bool this_flag, that_flag, the_other_flag;

interrupt this_isr()      {this_flag = true; /* cleanup */}
interrupt that_isr()      {that_flag = true; /* cleanup */}
interrupt the_other_isr() {the_other_flag = true; /* cleanup */}

main()
{
  // setup
  ...
  while (1)
  {
    if (this_flag)
    {
      do_this();      // resets this_flag
    }
    if (that_flag)
    {
      do_that();      // resets that_flag
    }
    if (the_other_flag)
    {
      do_the_other_thing():  // resets the_other_flag
    }
  }
}

In the third, you spring for an RTOS.  Technically you still only have 
virtual threads of control (since your processor can't really run two 
pieces of code at once), but you use semiphores and what not to create 
the same effect.

My question is:  Does anyone know a good tutorial that covers all of 
this, or at least techniques for implementing the task loop/state machine 
method?

Thanks.

-- 
Tim Wescott
Control systems and communications consulting
http://www.wescottdesign.com

Need to learn how to apply control theory in your embedded system?
"Applied Control Theory for Embedded Systems" by Tim Wescott
Elsevier/Newnes, http://www.wescottdesign.com/actfes/actfes.html

Tim Wescott wrote:

> I'm looking for a tutorial that I can forward to some folks.  I know of 
> three different ways of implementing software.  
> 
> In the first, you have just one real and virtual thread of control,

[...]

> In the second, you're too cheap to buy an RTOS, but you want to have 
> multiple virtual threads of control, so you use what I was taught to call 
> a task loop and what most folks seem to call a state machine

[...]

> In the third, you spring for an RTOS.

[...]

> My question is:  Does anyone know a good tutorial that covers all of 
> this, or at least techniques for implementing the task loop/state machine 
> method?

I don't know if there is a book with the necessary depth and breadth. 
May be you can write one? It will certainly be useful.

Jack Ganssle's "Art of designing embedded systems" has a chapter where 
he talks about interrupts and state machines.


Vladimir Vassilevsky
DSP and Mixed Signal Design Consultant
http://www.abvolt.com

On Feb 10, 4:03 pm, Tim Wescott <t...@seemywebsite.com> wrote:
> I'm looking for a tutorial that I can forward to some folks.  I know of
> three different ways of implementing software.

The rule of embedded software is that there is no real rule.  I just
finished an implementation with a mix of your case 1 and case 2:

>
> In the first, you have just one real and virtual thread of control, and
> the software goes something like:
>

While counting down / timing
  Data converter
  Update display
  Check for buttons
     Change state
     Finish tasks

When counter/timer expires, switch to:

>
> In the second, you're too cheap to buy an RTOS, but you want to have
> multiple virtual threads of control, so you use what I was taught to call
> a task loop and what most folks seem to call a state machine:
>

Button Change Interrupt Service Routine

While no Button Change
   Shutdown data converter
   Shutdown display
   Power down / sleep
   < wake up from interrupt >
   Update display
   Do data conversion
   Back to task loop

--------------------------------------------------

I can't say for sure if my software is a task loop or an interrupt
loop.
So, rules are made to be broken.

Tim Wescott wrote:

<snip>
> 
> My question is:  Does anyone know a good tutorial that covers all of 
> this, or at least techniques for implementing the task loop/state machine 
> method?

Believe it or not, LaBrosse's book covers each topic you cited with
example (pseudo) code and is quite tutorial in its approach in my
opinion.

Michael

"Tim Wescott"
> I'm looking for a tutorial that I can forward to some folks.  I know of
> three different ways of implementing software.
[..]
> In the third, you spring for an RTOS.  Technically you still only have
> virtual threads of control (since your processor can't really run two
> pieces of code at once), but you use semiphores and what not to create
> the same effect.
>
> My question is:  Does anyone know a good tutorial that covers all of
> this, or at least techniques for implementing the task loop/state machine
> method?

There is a book called "Patterns for time triggered embedded systems".

"... in the case of many embedded systems, the time triggered approach
has many advantages. Indeed, within industrial sectors where safety is
an obvious concern, such as the aerospace industry and increasingly
the automotive industry, time triggered techniques are widely used
because it is accepted both by the system developers and their
certification authorities, that they help improve reliability and
safety."

http://www.le.ac.uk/engineering/mjp9/pttes.html

"Lanarcam" <lanarcam1@yahoo.fr> a &#4294967295;crit dans le message news:
47b02654$0$27988$426a74cc@news.free.fr...
> "Tim Wescott"
>
> http://www.le.ac.uk/engineering/mjp9/pttes.html
>
And there is this free downloadable course

http://www.le.ac.uk/engineering/mjp9/pes1ohp_a4.pdf

On Feb 10, 7:03=A0pm, Tim Wescott <t...@seemywebsite.com> wrote:
> I'm looking for a tutorial that I can forward to some folks. =A0I know of
> three different ways of implementing software. =A0
>
> In the first, you have just one real and virtual thread of control, and
> the software goes something like:
>
> main()
> {
> =A0 // setup
> =A0 ...
> =A0 while(1)
> =A0 {
> =A0 =A0 do_this();
> =A0 =A0 delay(a_while);
> =A0 =A0 do_that();
> =A0 =A0 delay(a_while_longer);
> =A0 =A0 do_the_other_thing();
> =A0 =A0 delay(even_more);
> =A0 }
>
> }
>
> In the second, you're too cheap to buy an RTOS, but you want to have
> multiple virtual threads of control, so you use what I was taught to call
> a task loop and what most folks seem to call a state machine:
>
> bool this_flag, that_flag, the_other_flag;
>
> interrupt this_isr() =A0 =A0 =A0{this_flag =3D true; /* cleanup */}
> interrupt that_isr() =A0 =A0 =A0{that_flag =3D true; /* cleanup */}
> interrupt the_other_isr() {the_other_flag =3D true; /* cleanup */}
>
> main()
> {
> =A0 // setup
> =A0 ...
> =A0 while (1)
> =A0 {
> =A0 =A0 if (this_flag)
> =A0 =A0 {
> =A0 =A0 =A0 do_this(); =A0 =A0 =A0// resets this_flag
> =A0 =A0 }
> =A0 =A0 if (that_flag)
> =A0 =A0 {
> =A0 =A0 =A0 do_that(); =A0 =A0 =A0// resets that_flag
> =A0 =A0 }
> =A0 =A0 if (the_other_flag)
> =A0 =A0 {
> =A0 =A0 =A0 do_the_other_thing(): =A0// resets the_other_flag
> =A0 =A0 }
> =A0 }
>
> }
>
> In the third, you spring for an RTOS. =A0Technically you still only have
> virtual threads of control (since your processor can't really run two
> pieces of code at once), but you use semiphores and what not to create
> the same effect.
>
> My question is: =A0Does anyone know a good tutorial that covers all of
> this, or at least techniques for implementing the task loop/state machine
> method?
>
> Thanks.
>
> --
> Tim Wescott
> Control systems and communications consultinghttp://www.wescottdesign.com
>
> Need to learn how to apply control theory in your embedded system?
> "Applied Control Theory for Embedded Systems" by Tim Wescott
> Elsevier/Newnes,http://www.wescottdesign.com/actfes/actfes.html

The following article about hierarchical state machine design might
interest you:

http://www.eventhelix.com/RealtimeMantra/HierarchicalStateMachine.htm

You will also find a lot of articles about Real-time and embedded
programming at:

http://www.eventhelix.com/RealtimeMantra/

--
EventStudio 4.0 - http://www.Eventhelix.com/Eventstudio/
Sequence diagram based embedded system design tool

msg wrote:
> Tim Wescott wrote:
> 
> <snip>
>>
>> My question is:  Does anyone know a good tutorial that covers all of 
>> this, or at least techniques for implementing the task loop/state 
>> machine method?
> 
> Believe it or not, LaBrosse's book covers each topic you cited with
> example (pseudo) code and is quite tutorial in its approach in my
> opinion.
> 
> Michael

I don't have Labross's book, although I've skimmed it and watched 
someone use it to port mucus to a brand new chapter.  I don't care how 
good the programmer* is -- any time someone can prop a book up by their 
monitor, just type in code, and have it all work, it's a good book.

So I'll take that quite seriously.

* Well, he's a good programmer, too.

-- 

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

Do you need to implement control loops in software?
"Applied Control Theory for Embedded Systems" gives you just what it says.
See details at http://www.wescottdesign.com/actfes/actfes.html

Lanarcam schrieb:
> http://www.le.ac.uk/engineering/mjp9/pes1ohp_a4.pdf

That's very interesting! I'll keep this as a generic tutorial in case I
meet someone who is interested in such a course. It supplemented my
knowledge on Embedded stuffs as well :)

cheers,
Matthias
-- 
Matthias Arndt <marndt@asmsoftware.de>
PGP-Key: http://www.final-memory.org/files/marndt.asc   ICQ: 40358321
>>> Jabber: simonsunnyboy@jabber.ccc.de <<<

msg wrote:
> Tim Wescott wrote:
> 
> <snip>
>>
>> My question is:  Does anyone know a good tutorial that covers all of 
>> this, or at least techniques for implementing the task loop/state 
>> machine method?
> 
> Believe it or not, LaBrosse's book covers each topic you cited with
> example (pseudo) code and is quite tutorial in its approach in my
> opinion.

Considering that Jean LaBrosse appears to have 4 books in print:

http://www.amazon.com/s/ref=nb_ss_b/002-3183383-0799266?url=search-alias%3Dstripbooks&field-keywords=LaBrosse%2C+jean&x=0&y=0

Could you tell us to which one you are referring?


Thanks.

-- 
_____________________
Christopher R. Carlen
crobc@bogus-remove-me.sbcglobal.net
SuSE 9.1 Linux 2.6.5