Re: When exactly do you choose to use a RTOS (instead of a non-OS approach)?

From	Les Cargill <lcargill99@comcast.com>
Newsgroups	comp.arch.embedded
Subject	Re: When exactly do you choose to use a RTOS (instead of a non-OS approach)?
Date	2018-01-05 21:29 -0600
Organization	A noiseless patient Spider
Message-ID	<p2pfkf$7or$1@dont-email.me> (permalink)
References	(6 earlier) <p2j5mn$bev$2@dont-email.me> <p2jqj6$9jq$1@dont-email.me> <p2kotf$cu9$1@dont-email.me> <p2lve0$tuv$1@dont-email.me> <%jH3C.197195$nS6.171613@fx23.am4>

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Tom Gardner wrote:
> On 04/01/18 19:31, rickman wrote:
>> rickman wrote on 1/4/2018 3:33 AM:
>>> Les Cargill wrote on 1/3/2018 6:59 PM:
>>>> rickman wrote:
>>>>> Les Cargill wrote on 1/3/2018 7:07 AM:
>>>>>> rickman wrote:
>>>>>>> Ed Prochak wrote on 12/19/2017 11:19 AM:
>>>>>>>> On Saturday, December 16, 2017 at 12:56:31 PM UTC-5, Les Cargill 
>>>>>>>> wrote:
>>>>>>>>> Mike Perkins wrote:
>>>>>>>>>> On 09/12/2017 16:05, pozz wrote:
>>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>> I use it where I have a number of 'tasks' which then interact 
>>>>>>>>>> with each
>>>>>>>>>> other.
>>>>>>>>>>
>>>>>>>>>> If your system is a pure state machine then there is no need 
>>>>>>>>>> for an
>>>>>>>>>> RTOS.
>>>>>>>>>>
>>>>>>>>>
>>>>>>>>> Indeed. Indeed.
>>>>>>>>
>>>>>>>> If it is just one state machine. Then yes, indeed.
>>>>>>>> ed
>>>>>>>
>>>>>>> It can always be one state machine.  The only issue is how 
>>>>>>> complex the
>>>>>>> combined state machine is.
>>>>>>>
>>>>>>
>>>>>> It's always a case of "how long should a man's legs be?" Lincoln
>>>>>> is alleged to have said "long enough to touch the ground."
>>>>>>
>>>>>>> Actually the issue is not how many state machines you have.  It 
>>>>>>> is the
>>>>>>> timing requirements of the various state machines.  If your 
>>>>>>> timing is lax,
>>>>>>> sequential operation of multiple machines is easy.  But this 
>>>>>>> often becomes
>>>>>>> a huge discussion with everyone talking past each other.
>>>>>>>
>>>>>>
>>>>>> They should use state machines to keep track then :)
>>>>>>
>>>>>> If your system can be decomposed as roughly events cross
>>>>>> state, you have a snowball's chance of "understanding" it.
>>>>>
>>>>> Sorry, I don't know what this means "roughly events cross state".
>>>>>
>>>>>
>>>>
>>>> You are in state A. Event 42 occurs. Lookup.... ah, here -
>>>> if we get event 42 whilst in state A, we move to state B
>>>> and send message m.
>>>
>>> So what makes that so hard to understand?
>>
>> To be more explicit, I think every FSM I've ever coded was along the 
>> lines of a
>> case statement on the state with IF conditions on all the interesting 
>> inputs.  I
>> find this structure to be self documenting if the signal names are 
>> chosen well.
>>
>> Why is this structure hard to understand?
> 
> I've seen a commercial case where that type of structure was
> mutated by people under pressure to:
>   - have a single state machine for all different customers
>   - make the minimum change
>   - do it fast
>   - where the original designers had left
>   - a custom domain specific language, ugh
> 
> The result was an unholy unmaintainable mess, with
> if-then-elses nested up to 10 (ten!) deep.
> 

Eh, doing it totally, totally wrong. With all due respect - you really
need a configuration system managed well within the code itself, and
customer specializations are but different settings.

On one product, the "model number' was nothing more than a name
that pointed to a hard table of defaults for the configuration,
and further config changes were possible. If the support
people requested it, we'd grow a model number when they got too painful.

That being said - OO and configuration go together like chalk and cheese
:)

> Completely insane, of course.
> 


Well, yeah. You can make anything disgusting
if you work hard enough :)

> My preference is for a dispatch table based on event+state,
> since that forces you to consider all possibilities. 

Yup yup. And you can generate a test vector for it with combinators.
Then testing essentially becomes compressing the output - tedious, but
... rewarding.

If the tested FSM is properly tested, then all remaining
defects are 1) either tweak/tone of unrealistic expectations or
2) hardware bugs.

> The
> dispatch table can be either a 2D array of function pointers,
> or inherent in an OOP inheritance hierarchy where the
> hierarchy is a direct mirror of the state hierarchy.


There's something to be said for the 2d approach. It's
more canonical ( and more normal ) for one.

-- 
Les Cargill

Thread

Re: When exactly do you choose to use a RTOS (instead of a non-OS approach)? Mike Perkins <spam@spam.com> - 2017-12-10 14:56 +0000
  Re: When exactly do you choose to use a RTOS (instead of a non-OS approach)? Les Cargill <lcargill99@comcast.com> - 2017-12-16 11:58 -0600
    Re: When exactly do you choose to use a RTOS (instead of a non-OS approach)? Ed Prochak <edprochak@gmail.com> - 2017-12-19 08:19 -0800
      Re: When exactly do you choose to use a RTOS (instead of a non-OS approach)? rickman <gnuarm@gmail.com> - 2017-12-19 11:51 -0500
        Re: When exactly do you choose to use a RTOS (instead of a non-OS approach)? Ed Prochak <edprochak@gmail.com> - 2018-01-02 14:58 -0800
        Re: When exactly do you choose to use a RTOS (instead of a non-OS approach)? Les Cargill <lcargill99@comcast.com> - 2018-01-03 06:07 -0600
          Re: When exactly do you choose to use a RTOS (instead of a non-OS approach)? rickman <gnuarm.deletethisbit@gmail.com> - 2018-01-03 12:59 -0500
            Re: When exactly do you choose to use a RTOS (instead of a non-OS approach)? Les Cargill <lcargill99@comcast.com> - 2018-01-03 17:59 -0600
              Re: When exactly do you choose to use a RTOS (instead of a non-OS approach)? rickman <gnuarm.deletethisbit@gmail.com> - 2018-01-04 03:33 -0500
                Re: When exactly do you choose to use a RTOS (instead of a non-OS approach)? rickman <gnuarm.deletethisbit@gmail.com> - 2018-01-04 14:31 -0500
                Re: When exactly do you choose to use a RTOS (instead of a non-OS approach)? Rob Gaddi <rgaddi@highlandtechnology.invalid> - 2018-01-04 11:56 -0800
                Re: When exactly do you choose to use a RTOS (instead of a non-OS approach)? Les Cargill <lcargill99@comcast.com> - 2018-01-04 21:46 -0600
                Re: When exactly do you choose to use a RTOS (instead of a non-OS approach)? Paul Rubin <no.email@nospam.invalid> - 2018-01-04 16:46 -0800
                Re: When exactly do you choose to use a RTOS (instead of a non-OS approach)? Les Cargill <lcargill99@comcast.com> - 2018-01-04 21:47 -0600
                Re: When exactly do you choose to use a RTOS (instead of a non-OS approach)? rickman <gnuarm.deletethisbit@gmail.com> - 2018-01-06 18:55 -0500
                Re: When exactly do you choose to use a RTOS (instead of a non-OS approach)? Tom Gardner <spamjunk@blueyonder.co.uk> - 2018-01-07 00:54 +0000
                Re: When exactly do you choose to use a RTOS (instead of a non-OS approach)? Paul Rubin <no.email@nospam.invalid> - 2018-01-07 13:41 -0800
                Re: When exactly do you choose to use a RTOS (instead of a non-OS approach)? Tom Gardner <spamjunk@blueyonder.co.uk> - 2018-01-07 23:32 +0000
                Re: When exactly do you choose to use a RTOS (instead of a non-OS approach)? rickman <gnuarm.deletethisbit@gmail.com> - 2018-01-10 10:33 -0500
                Re: When exactly do you choose to use a RTOS (instead of a non-OS approach)? Tom Gardner <spamjunk@blueyonder.co.uk> - 2018-01-10 16:29 +0000
                Re: When exactly do you choose to use a RTOS (instead of a non-OS approach)? upsidedown@downunder.com - 2018-01-08 08:11 +0200
                Re: When exactly do you choose to use a RTOS (instead of a non-OS approach)? Paul Rubin <no.email@nospam.invalid> - 2018-01-07 23:05 -0800
                Re: When exactly do you choose to use a RTOS (instead of a non-OS approach)? upsidedown@downunder.com - 2018-01-08 10:06 +0200
                Re: When exactly do you choose to use a RTOS (instead of a non-OS approach)? David Brown <david.brown@hesbynett.no> - 2018-01-08 10:27 +0100
                Re: When exactly do you choose to use a RTOS (instead of a non-OS approach)? Paul Rubin <no.email@nospam.invalid> - 2018-01-08 09:56 -0800
                Re: When exactly do you choose to use a RTOS (instead of a non-OS approach)? Tom Gardner <spamjunk@blueyonder.co.uk> - 2018-01-08 18:39 +0000
                Re: When exactly do you choose to use a RTOS (instead of a non-OS approach)? Paul Rubin <no.email@nospam.invalid> - 2018-01-08 12:20 -0800
                Re: When exactly do you choose to use a RTOS (instead of a non-OS approach)? Tom Gardner <spamjunk@blueyonder.co.uk> - 2018-01-08 22:11 +0000
                Re: When exactly do you choose to use a RTOS (instead of a non-OS approach)? David Brown <david.brown@hesbynett.no> - 2018-01-08 22:26 +0100
                Re: When exactly do you choose to use a RTOS (instead of a non-OS approach)? Tom Gardner <spamjunk@blueyonder.co.uk> - 2018-01-08 22:23 +0000
                Re: When exactly do you choose to use a RTOS (instead of a non-OS approach)? Paul Rubin <no.email@nospam.invalid> - 2018-01-08 14:44 -0800
                Re: When exactly do you choose to use a RTOS (instead of a non-OS approach)? Tom Gardner <spamjunk@blueyonder.co.uk> - 2018-01-08 23:06 +0000
                Re: When exactly do you choose to use a RTOS (instead of a non-OS approach)? Tom Gardner <spamjunk@blueyonder.co.uk> - 2018-01-08 10:02 +0000
                Re: When exactly do you choose to use a RTOS (instead of a non-OS approach)? Les Cargill <lcargill99@comcast.com> - 2018-01-08 17:34 -0600
                Re: When exactly do you choose to use a RTOS (instead of a non-OS approach)? rickman <gnuarm.deletethisbit@gmail.com> - 2018-01-06 22:29 -0500
                Re: When exactly do you choose to use a RTOS (instead of a non-OS approach)? Paul Rubin <no.email@nospam.invalid> - 2018-01-07 00:46 -0800
                Re: When exactly do you choose to use a RTOS (instead of a non-OS approach)? Les Cargill <lcargill99@comcast.com> - 2018-01-04 21:44 -0600
                Re: When exactly do you choose to use a RTOS (instead of a non-OS approach)? Tom Gardner <spamjunk@blueyonder.co.uk> - 2018-01-05 09:12 +0000
                Re: When exactly do you choose to use a RTOS (instead of a non-OS approach)? Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> - 2018-01-05 21:40 -0500
                Re: When exactly do you choose to use a RTOS (instead of a non-OS approach)? Les Cargill <lcargill99@comcast.com> - 2018-01-05 21:29 -0600
                Re: When exactly do you choose to use a RTOS (instead of a non-OS approach)? Tom Gardner <spamjunk@blueyonder.co.uk> - 2018-01-06 09:10 +0000
                Re: When exactly do you choose to use a RTOS (instead of a non-OS approach)? Les Cargill <lcargill99@comcast.com> - 2018-01-06 16:35 -0600
                Re: When exactly do you choose to use a RTOS (instead of a non-OS approach)? Tom Gardner <spamjunk@blueyonder.co.uk> - 2018-01-07 01:04 +0000
                Re: When exactly do you choose to use a RTOS (instead of a non-OS approach)? Tom Gardner <spamjunk@blueyonder.co.uk> - 2018-01-06 09:17 +0000
                Re: When exactly do you choose to use a RTOS (instead of a non-OS approach)? Les Cargill <lcargill99@comcast.com> - 2018-01-06 16:37 -0600
                Re: When exactly do you choose to use a RTOS (instead of a non-OS approach)? Tom Gardner <spamjunk@blueyonder.co.uk> - 2018-01-07 01:11 +0000
                Re: When exactly do you choose to use a RTOS (instead of a non-OS approach)? Paul Rubin <no.email@nospam.invalid> - 2018-01-06 17:31 -0800
                Re: When exactly do you choose to use a RTOS (instead of a non-OS approach)? Tom Gardner <spamjunk@blueyonder.co.uk> - 2018-01-07 01:52 +0000
                Re: When exactly do you choose to use a RTOS (instead of a non-OS approach)? Paul Rubin <no.email@nospam.invalid> - 2018-01-07 00:39 -0800
                Re: When exactly do you choose to use a RTOS (instead of a non-OS approach)? Tom Gardner <spamjunk@blueyonder.co.uk> - 2018-01-07 09:55 +0000
                Re: When exactly do you choose to use a RTOS (instead of a non-OS approach)? Paul Rubin <no.email@nospam.invalid> - 2018-01-07 10:43 -0800
                Re: When exactly do you choose to use a RTOS (instead of a non-OS approach)? Tom Gardner <spamjunk@blueyonder.co.uk> - 2018-01-07 19:35 +0000
                Re: When exactly do you choose to use a RTOS (instead of a non-OS approach)? rickman <gnuarm.deletethisbit@gmail.com> - 2018-01-06 19:06 -0500
                Re: When exactly do you choose to use a RTOS (instead of a non-OS approach)? Paul Rubin <no.email@nospam.invalid> - 2018-01-06 16:58 -0800
                Re: When exactly do you choose to use a RTOS (instead of a non-OS approach)? rickman <gnuarm.deletethisbit@gmail.com> - 2018-01-06 22:37 -0500
                Re: When exactly do you choose to use a RTOS (instead of a non-OS approach)? Paul Rubin <no.email@nospam.invalid> - 2018-01-07 00:58 -0800
                Re: When exactly do you choose to use a RTOS (instead of a non-OS approach)? rickman <gnuarm.deletethisbit@gmail.com> - 2018-01-07 09:32 -0500
                Re: When exactly do you choose to use a RTOS (instead of a non-OS approach)? Paul Rubin <no.email@nospam.invalid> - 2018-01-07 10:53 -0800
                Re: When exactly do you choose to use a RTOS (instead of a non-OS approach)? rickman <gnuarm.deletethisbit@gmail.com> - 2018-01-10 11:40 -0500
                Re: When exactly do you choose to use a RTOS (instead of a non-OS approach)? Tom Gardner <spamjunk@blueyonder.co.uk> - 2018-01-07 01:14 +0000
                Re: When exactly do you choose to use a RTOS (instead of a non-OS approach)? rickman <gnuarm.deletethisbit@gmail.com> - 2018-01-06 18:57 -0500
                Re: When exactly do you choose to use a RTOS (instead of a non-OS approach)? Tom Gardner <spamjunk@blueyonder.co.uk> - 2018-01-07 01:17 +0000
                Re: When exactly do you choose to use a RTOS (instead of a non-OS approach)? rickman <gnuarm.deletethisbit@gmail.com> - 2018-01-06 22:40 -0500
                Re: When exactly do you choose to use a RTOS (instead of a non-OS approach)? Tom Gardner <spamjunk@blueyonder.co.uk> - 2018-01-07 09:59 +0000

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