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Re: Do you use FSMs or HSMs?

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Il 06/02/2017 15:56, QL ha scritto:
> Let me start with the full disclosure: I'm the author of the book
> "Practical UML Statecharts in C/C++, 2nd Edition" and I run a company
> called Quantum Leaps that makes open-source state machine software
> frameworks and a free state machine modeling tool. The company website
> is:
>
> http://www.state-machine.com

Yes, I know your book and your QP/C implementation, mainly your QEP 
processor (the implementation of state machines).

I think it's the only well-designed HSM implementation in C.


> So, yes, I also strongly believe that hierarchical state machines (a.k.a.
> UML statecharts) combined with event-driven programming are the best way
> to go when it comes to developing real-time embedded software.
>
> From my two decades of experience, however, I see that the biggest
> obstacle in adopting state machines is the required paradigm shift from
> sequential programming based on blocking (like blocking on a semaphore or
> a time delay in a traditional RTOS or a "superloop") and the event-driven
> programming based on run-to-completion event processing without blocking
> (like in a state machine).

Yes, I agree with you. I always try to reduce all my project to a fully 
event-driven machine, but it's very difficult.

Many parts of the project can be represented and implemented in a simple 
and efficient way with an HSM. However for me it's difficult to 
implement other parts with an HSM with an event-driven only paradigm.

Example. If the engine must be off when an interlock is open, I put the 
following code in the superloop:
    if (interlock_is_open()) engine_off();
In this way I am *sure* this happens. With an event-driven approach, I 
have to create two different signals: INTERLOCK_OPEN, INTERLOCK_CLOSED. 
I have to be sure the INTERLOCK_OPEN signal is processed and lead to the 
switching off of the engine.

I usually tend to avoid blocking tasks. When I face it, I try to split 
it in sub-tasks... a state-machine. However it's difficult for 
communication protocols (I2C, RS485, ...) and/or third-parties libraries 
(GUI).


> Anyway, if you are seriously interested in (hierarchical) state machines
> for embedded real-time systems I would recommend to start with the key
> concepts:
>
> http://www.state-machine.com/doc/concepts.html
>
>
> You might also wish to try the free state machine modeling tool called QM,
> which allows you to draw hierarchical state machine diagrams and
> automatically generate production-quality C or C++ code from them:
>
> http://www.state-machine.com/qm

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Do you use FSMs or HSMs? pozz <pozzugno@gmail.com> - 2017-02-06 10:43 +0100
  Re: Do you use FSMs or HSMs? Don Y <blockedofcourse@foo.invalid> - 2017-02-06 03:20 -0700
  Re: Do you use FSMs or HSMs? Dave Nadler <drn@nadler.com> - 2017-02-06 06:38 -0800
  Re: Do you use FSMs or HSMs? "QL" <80499@EmbeddedRelated> - 2017-02-06 08:56 -0600
    Re: Do you use FSMs or HSMs? Don Y <blockedofcourse@foo.invalid> - 2017-02-06 12:13 -0700
    Re: Do you use FSMs or HSMs? jim.brakefield@ieee.org - 2017-02-06 16:52 -0800
      Re: Do you use FSMs or HSMs? Don Y <blockedofcourse@foo.invalid> - 2017-02-06 18:11 -0700
      Re: Do you use FSMs or HSMs? Les Cargill <lcargill99@comcast.com> - 2017-02-06 23:32 -0600
    Re: Do you use FSMs or HSMs? pozz <pozzugno@gmail.com> - 2017-02-07 10:39 +0100
  Re: Do you use FSMs or HSMs? John Speth <johnspeth@yahoo.com> - 2017-02-06 09:17 -0800
    Re: Do you use FSMs or HSMs? Tom Gardner <spamjunk@blueyonder.co.uk> - 2017-02-06 18:03 +0000
      Re: Do you use FSMs or HSMs? Don Y <blockedofcourse@foo.invalid> - 2017-02-06 11:56 -0700
        Re: Do you use FSMs or HSMs? Tom Gardner <spamjunk@blueyonder.co.uk> - 2017-02-06 20:34 +0000
          Re: Do you use FSMs or HSMs? Don Y <blockedofcourse@foo.invalid> - 2017-02-06 14:19 -0700
            Re: Do you use FSMs or HSMs? Tom Gardner <spamjunk@blueyonder.co.uk> - 2017-02-06 22:12 +0000
              Re: Do you use FSMs or HSMs? Don Y <blockedofcourse@foo.invalid> - 2017-02-06 15:29 -0700
              Re: Do you use FSMs or HSMs? Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> - 2017-02-08 12:15 -0500
                Re: Do you use FSMs or HSMs? Tom Gardner <spamjunk@blueyonder.co.uk> - 2017-02-08 23:52 +0000
                Re: Do you use FSMs or HSMs? Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> - 2017-02-08 19:59 -0500
              Re: Do you use FSMs or HSMs? Steve Watt <steve.removethis@Watt.COM> - 2017-02-17 00:30 +0000
                Re: Do you use FSMs or HSMs? Tom Gardner <spamjunk@blueyonder.co.uk> - 2017-02-17 00:44 +0000
            Re: Do you use FSMs or HSMs? Clifford Heath <no.spam@please.net> - 2017-02-07 10:12 +1100
              Re: Do you use FSMs or HSMs? Les Cargill <lcargill99@comcast.com> - 2017-02-06 23:36 -0600
                Re: Do you use FSMs or HSMs? George Neuner <gneuner2@comcast.net> - 2017-02-07 03:15 -0500
                Re: Do you use FSMs or HSMs? Les Cargill <lcargill99@comcast.com> - 2017-02-10 17:41 -0600
                Re: Do you use FSMs or HSMs? Clifford Heath <no.spam@please.net> - 2017-02-07 19:56 +1100
                Re: Do you use FSMs or HSMs? Paul Rubin <no.email@nospam.invalid> - 2017-02-07 01:30 -0800
                Re: Do you use FSMs or HSMs? Clifford Heath <no.spam@please.net> - 2017-02-07 20:42 +1100
                Re: Do you use FSMs or HSMs? Paul Rubin <no.email@nospam.invalid> - 2017-02-07 02:46 -0800
                Re: Do you use FSMs or HSMs? Clifford Heath <no.spam@please.net> - 2017-02-08 00:27 +1100
  Re: Do you use FSMs or HSMs? Paul Rubin <no.email@nospam.invalid> - 2017-02-06 18:35 -0800
    Re: Do you use FSMs or HSMs? Don Y <blockedofcourse@foo.invalid> - 2017-02-06 21:50 -0700
    Re: Do you use FSMs or HSMs? Les Cargill <lcargill99@comcast.com> - 2017-02-06 23:39 -0600
      Re: Do you use FSMs or HSMs? Paul Rubin <no.email@nospam.invalid> - 2017-02-06 23:20 -0800
        Re: Do you use FSMs or HSMs? Les Cargill <lcargill99@comcast.com> - 2017-02-10 17:47 -0600
          Re: Do you use FSMs or HSMs? Paul Rubin <no.email@nospam.invalid> - 2017-02-10 16:11 -0800
            Re: Do you use FSMs or HSMs? Les Cargill <lcargill99@comcast.com> - 2017-02-11 15:43 -0600
  Re: Do you use FSMs or HSMs? Les Cargill <lcargill99@comcast.com> - 2017-02-06 23:24 -0600

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