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Re: Design pattern: refresh-based or event-based?

From pozz <pozzugno@gmail.com>
Newsgroups comp.arch.embedded
Subject Re: Design pattern: refresh-based or event-based?
Date 2015-07-22 07:01 +0200
Organization A noiseless patient Spider
Message-ID <mon7vk$8at$1@dont-email.me> (permalink)
References <moku8e$6sf$1@dont-email.me> <d16su5FufvjU1@mid.dfncis.de>

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Il 21/07/2015 14:40, Hans-Bernhard Bröker ha scritto:
> Am 21.07.2015 um 10:02 schrieb pozz:
>
>> Refresh-based is very simple: every 20ms, 100ms, 500ms or 1s a refresh
>> function is called. This function redraws *everything* on the dashboard
>> based on the current values collected on the bus.
>
>> The thing I don't like with this approach is that it could be time
>> consuming.If the values change slowly, most probably only 1-5 values
>  > really change since the last refresh. Why do I redraw everything?
>
> Well, you did post this to c.a.embedded, where we usually assume that
> some degree of real-time constraint will be in place.  In the case of
> your display update that means the system almost certainly _must_ be
> able to handle the case where everything _does_ change, anyway, and
> without breaking the timing constraints.  So if you must be able to do
> it sometimes, it may well be better to just do it all the time, if only
> to reduce the variation of CPU load caused by it, and to increase
> overall predictability of the system's behaviour.

I got your point, but HMIs are't usually hard real-time systems. I could 
accept a short delay in opening a new screen (completely redraw of the 
display, think of opening an application on Windows), but I'd prefer to 
have a responsive interface after this time.

If I don't have a powerful graphical CPU, one solution to improve 
responsiveness could be to update on the display only the values that 
really change. Mostly if most of them change very slowly.


> The fact that it's a lot easier to do it that way comes an additional
> bonus.

Indeed many times I use a refresh-based mechanism.

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Design pattern: refresh-based or event-based? pozz <pozzugno@gmail.com> - 2015-07-21 10:02 +0200
  Re: Design pattern: refresh-based or event-based? upsidedown@downunder.com - 2015-07-21 11:37 +0300
    Re: Design pattern: refresh-based or event-based? pozz <pozzugno@gmail.com> - 2015-07-21 11:00 +0200
      Re: Design pattern: refresh-based or event-based? Dimiter_Popoff <dp@tgi-sci.com> - 2015-07-22 01:34 +0300
        Re: Design pattern: refresh-based or event-based? pozz <pozzugno@gmail.com> - 2015-07-22 06:57 +0200
          Re: Design pattern: refresh-based or event-based? Paul Rubin <no.email@nospam.invalid> - 2015-07-21 23:02 -0700
            Re: Design pattern: refresh-based or event-based? pozz <pozzugno@gmail.com> - 2015-07-22 09:17 +0200
              Re: Design pattern: refresh-based or event-based? Paul Rubin <no.email@nospam.invalid> - 2015-07-22 00:23 -0700
        Re: Design pattern: refresh-based or event-based? upsidedown@downunder.com - 2015-07-22 10:02 +0300
          Re: Design pattern: refresh-based or event-based? Dimiter_Popoff <dp@tgi-sci.com> - 2015-07-22 19:48 +0300
            Re: Design pattern: refresh-based or event-based? pozz <pozzugno@gmail.com> - 2015-07-23 09:04 +0200
              Re: Design pattern: refresh-based or event-based? Dimiter_Popoff <dp@tgi-sci.com> - 2015-07-23 10:29 +0300
                Re: Design pattern: refresh-based or event-based? raimond.dragomir@gmail.com - 2015-07-31 02:34 -0700
  Re: Design pattern: refresh-based or event-based? Don Y <this@is.not.me.com> - 2015-07-21 03:16 -0700
  Re: Design pattern: refresh-based or event-based? Hans-Bernhard Bröker <HBBroeker@t-online.de> - 2015-07-21 14:40 +0200
    Re: Design pattern: refresh-based or event-based? pozz <pozzugno@gmail.com> - 2015-07-22 07:01 +0200
      Re: Design pattern: refresh-based or event-based? Stefan Reuther <stefan.news@arcor.de> - 2015-07-22 18:30 +0200
        Re: Design pattern: refresh-based or event-based? Paul Rubin <no.email@nospam.invalid> - 2015-07-22 10:55 -0700
  Re: Design pattern: refresh-based or event-based? Paul Rubin <no.email@nospam.invalid> - 2015-07-21 08:26 -0700
    Re: Design pattern: refresh-based or event-based? pozz <pozzugno@gmail.com> - 2015-07-22 07:04 +0200
      Re: Design pattern: refresh-based or event-based? Paul Rubin <no.email@nospam.invalid> - 2015-07-21 23:13 -0700
        Re: Design pattern: refresh-based or event-based? pozz <pozzugno@gmail.com> - 2015-07-22 09:24 +0200
          Re: Design pattern: refresh-based or event-based? Paul Rubin <no.email@nospam.invalid> - 2015-07-22 08:26 -0700
            Re: Design pattern: refresh-based or event-based? pozz <pozzugno@gmail.com> - 2015-07-23 09:00 +0200
  Re: Design pattern: refresh-based or event-based? hamilton <hamilton@nothere.com> - 2015-07-21 14:07 -0600
    Re: Design pattern: refresh-based or event-based? Don Y <this@is.not.me.com> - 2015-07-21 13:12 -0700
  Re: Design pattern: refresh-based or event-based? Andrew Smallshaw <andrews@sdf.lonestar.org> - 2015-07-22 00:19 +0000
    Re: Design pattern: refresh-based or event-based? Paul Rubin <no.email@nospam.invalid> - 2015-07-21 18:09 -0700
      Re: Design pattern: refresh-based or event-based? Andrew Smallshaw <andrews@sdf.lonestar.org> - 2015-07-22 21:18 +0000
        Re: Design pattern: refresh-based or event-based? Paul Rubin <no.email@nospam.invalid> - 2015-07-22 23:17 -0700
    Re: Design pattern: refresh-based or event-based? pozz <pozzugno@gmail.com> - 2015-07-22 07:20 +0200
    Re: Design pattern: refresh-based or event-based? upsidedown@downunder.com - 2015-07-22 10:53 +0300
  Re: Design pattern: refresh-based or event-based? pozz <pozzugno@gmail.com> - 2015-07-22 07:32 +0200

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