Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > comp.arch.embedded > #13863

Re: Counting 2ms long pulses on several input pins

Show all headers | View raw

Hi Arlett,

On 9/24/2013 11:30 AM, Arlet Ottens wrote:
> On 09/24/2013 08:13 PM, Don Y wrote:
>
>> Chances are, the limitations of your debounce algorithm (along
>> with most other algorithms in your design) aren't spelled out
>> in simple terms in a place where someone wanting to modify the
>> hardware/software/specification can quickly review them for the
>> downside consequences of any proposed changes.
>>
>> This leads to those annoying pointy-head conversations where
>> you have to tell your boss/client that this "simple" change is
>> going to take a week to implement/test:  "Huh?  Why can't we just
>> use this different switch??  Why can't we just change the cam
>> dwell to 7 degrees from 10??  etc."
>>
>> Then, as their frustration mounts, trying to reassure them that
>> there was a *reason* you "crippled" (in their eyes) the algorithm
>> in this way.  So, they should, in a perverse sense, be HAPPY that
>> it will take a week! (otherwise, it would imply you were using
>> an inappropriate algorithm).
>
> Instead of 'crippled', I'd use the term 'simplified'. It's a 3 line
> piece of code, driven by a constant timer, with only 1 parameter: the
> timer interval. It's hard to imagine any modification would require a week.

The "modification" would be fixing it to handle real world
constraints.

E.g., what if you have to debounce the *trailing* edge of the
signal as well?  Or, if the signal bounces for its *entire*
"operated" period (i.e., it never "settles" before the cam
has "passed" completely)?  Or if each switch operates at
different rates (some fast and some slow).  Or if "where" (in
the cam cycle) the output is generated needs to be tweeked?
Or, if the profile of the cam is altered (e.g., inverted so
what was a trailing edge now becomes the leading edge) -- for
example, to convert a very low dwell angle signal to the
complementary high dwell signal (cuz little blips on cams
wear down and become even smaller/narrower; while short
"notches" have lots more room to "grow into")

Or if the algorithm doesn't initialize favorably ("As soon as
we turn the power on, it reports a leading edge of a cam even
though the mechanism hasn't started moving, yet"!)

> In fact, a more complicated algorithm is more likely to be misunderstood
> and messed up later.

A more complicated algorithm is more likely to be implemented
correctly *once* and copied thereafter.  Then, tweeked in
well defined ways ("to generate signal on switch *release*,
insert statement HERE")

E.g., for keyboards/keypads, I implement up/down encoders:
X has been depressed; X has been released

Back to comp.arch.embedded | Previous | Next — Previous in thread | Next in thread | Find similar | Unroll thread

Thread

Counting 2ms long pulses on several input pins pozz <pozzugno@gmail.com> - 2013-09-23 23:42 +0200
  Re: Counting 2ms long pulses on several input pins mike <ham789@netzero.net> - 2013-09-23 15:00 -0700
  Re: Counting 2ms long pulses on several input pins Don Y <this@isnotme.com> - 2013-09-23 16:12 -0700
  Re: Counting 2ms long pulses on several input pins Paul Rubin <no.email@nospam.invalid> - 2013-09-23 18:45 -0700
    Re: Counting 2ms long pulses on several input pins Arlet Ottens <usenet+5@c-scape.nl> - 2013-09-24 08:06 +0200
      Re: Counting 2ms long pulses on several input pins Don Y <this@isnotme.com> - 2013-09-24 00:37 -0700
        Re: Counting 2ms long pulses on several input pins Arlet Ottens <usenet+5@c-scape.nl> - 2013-09-24 10:24 +0200
          Re: Counting 2ms long pulses on several input pins Paul Rubin <no.email@nospam.invalid> - 2013-09-24 02:05 -0700
            Re: Counting 2ms long pulses on several input pins Arlet Ottens <usenet+5@c-scape.nl> - 2013-09-24 11:01 +0200
          Re: Counting 2ms long pulses on several input pins Don Y <this@isnotme.com> - 2013-09-24 09:55 -0700
            Re: Counting 2ms long pulses on several input pins Tom Gardner <spamjunk@blueyonder.co.uk> - 2013-09-24 18:13 +0100
              Re: Counting 2ms long pulses on several input pins Don Y <this@isnotme.com> - 2013-09-24 11:03 -0700
            Re: Counting 2ms long pulses on several input pins Arlet Ottens <usenet+5@c-scape.nl> - 2013-09-24 19:38 +0200
              Re: Counting 2ms long pulses on several input pins Don Y <this@isnotme.com> - 2013-09-24 11:13 -0700
                Re: Counting 2ms long pulses on several input pins Arlet Ottens <usenet+5@c-scape.nl> - 2013-09-24 20:30 +0200
                Re: Counting 2ms long pulses on several input pins Paul E Bennett <Paul_E.Bennett@topmail.co.uk> - 2013-09-24 21:20 +0100
                Re: Counting 2ms long pulses on several input pins Don Y <this@isnotme.com> - 2013-09-24 16:08 -0700
    Re: Counting 2ms long pulses on several input pins Don Y <this@isnotme.com> - 2013-09-24 00:34 -0700
  Re: Counting 2ms long pulses on several input pins Andrew Smallshaw <andrews@sdf.lonestar.org> - 2013-09-24 04:31 +0000
  Re: Counting 2ms long pulses on several input pins Paul E Bennett <Paul_E.Bennett@topmail.co.uk> - 2013-09-24 11:15 +0100
    Re: Counting 2ms long pulses on several input pins Paul <paul@pcserviceselectronics.co.uk> - 2013-09-24 15:51 +0100
  Re: Counting 2ms long pulses on several input pins pozz <pozzugno@gmail.com> - 2013-09-25 00:33 +0200
    Re: Counting 2ms long pulses on several input pins Don Y <this@isnotme.com> - 2013-09-24 16:36 -0700
      Re: Counting 2ms long pulses on several input pins pozz <pozzugno@gmail.com> - 2013-09-25 07:39 +0200
        Re: Counting 2ms long pulses on several input pins Don Y <this@isnotme.com> - 2013-09-24 23:37 -0700
          Re: Counting 2ms long pulses on several input pins pozz <pozzugno@gmail.com> - 2013-09-27 15:54 +0200
            Re: Counting 2ms long pulses on several input pins Don Y <this@isnotme.com> - 2013-09-27 12:35 -0700
    Re: Counting 2ms long pulses on several input pins mike <ham789@netzero.net> - 2013-09-24 16:43 -0700
  Re: Counting 2ms long pulses on several input pins j.m.granville@gmail.com - 2013-09-24 17:32 -0700
    Re: Counting 2ms long pulses on several input pins Tauno Voipio <tauno.voipio@notused.fi.invalid> - 2013-09-25 09:52 +0300
      Re: Counting 2ms long pulses on several input pins Don Y <this@isnotme.com> - 2013-09-25 00:09 -0700
        Re: Counting 2ms long pulses on several input pins j.m.granville@gmail.com - 2013-09-25 16:53 -0700

csiph-web