RE: [ts-7000] Re: only DIO 1,3,5,7 works

[salva g <>]

ok, but can you have a look to this,

http://www.serasidis.gr/circuits/lcd_keys/lcd_keys.htm

do you think it could be impplemented in the TS7800?
i think that if we go line by line put them low-to-high and then, read the switches pressed(of 4), next line and so on...and very very fast!, we could have it
or (probably) am i wrong?

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To:
From:
Date: Tue, 29 Sep 2009 18:12:24 -0400
Subject: Re: [ts-7000] Re: only DIO 1,3,5,7 works

 

salva g wrote:

  ...and could be pressed any switches i want at the same time? or only one?

No, think of it as a 4x4 grid, sorta like this.

  1  2  3  4
  |  |  |  |
--+--+--+--+-- A
  |  |  |  |
--+--+--+--+-- B
  |  |  |  |
--+--+--+--+-- C
  |  |  |  |
--+--+--+--+-- D
  |  |  |  |


Where ever there is a + is a button, ----'s (A-D) are the output wires (four of them) and |  | (1-4) are the input wires (four of them)

Now, if line A is high and you press say A3 and B3 then the B line effectively becomes high as well.  If you pressed A3, B3 and B1 down then your program would "see" A3 and A1 as being pressed. Now if the B line is pulled low you've just created a short which is why it's always a good idea to put current limit resistors in series with any output.

You can block this interaction by using diodes, if you want more info I'd look up "matrix keypad schematic" or something like that online.  It's neat to note that most keyboards for your computer work in a similar way.

--
Jason Stahls

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