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'[OT] 4x4 Hex Keypad'
1999\09\06@232804 by netquake

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Hello!

I have an hex keypad with 16 pins (one for each key) and 1 common.
Can I use this type of keypad in a project that requires a 4x4 matrix
keypad (8 lines/pins)(row/column selection)?
How can I do that?

Sorry for my ignorance.

And thank you for your time.
Special thanks to those people that always find the time and
knowledge to answer my questions. I owe them...
------------------------------------
netQ <spam_OUTnetquakeTakeThisOuTspaminnocent.com>
http://virtuaweb.com/picprog
"Home of amateur PIC programmers..."

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1999\09\07@010037 by paulb

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German wrote:

> I have a hex keypad with 16 pins (one for each key) and 1 common.
> Can I use this type of keypad in a project that requires a 4x4 matrix
> keypad (8 lines/pins)(row/column selection)?

 Yes, but you aren't going to like the answer!  You'll need four 4066
chips and two octal SIL resistor packs for pull-downs.  Each key and
pull-down controls one "switch" which makes the matching matrix closure.

 This *is* very useful if you need for example, to control a remote
control (IR) sender to control some device for four functions, and there
is a cute trick using a pocket calculator as a dirt-cheap item counter.

 The message for your application however is - you need a matrix
keyboard and they are usually inexpensive and common.  Note that some
keyboards (real old Touch-Tone telephone pads) have a common with rows
and columns.  In that case of course, you don't need to use the common
and it would do the job.
--
 Cheers,
       Paul B.

1999\09\07@012901 by Tony Nixon

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Maybe a 74C150 16 line to 1 line multiplexer.

--
Best regards

Tony

http://www.picnpoke.com
Email .....salesKILLspamspam@spam@picnpoke.com

1999\09\07@024309 by Tony Nixon

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"Paul B. Webster VK2BZC" wrote:
>
> Hello Tony.
>
> > Maybe a 74C150 16 line to 1 line multiplexer.
>
>   Now how would you use that?
>

I could be wrong (it's been a long day) but I thought you could set a 4
bit code to sample any one of the 16 inputs. There are inverted, but
that doesn't matter. If a key is pressed on the input line that
corresponds to the 4 bit data, then the output state will be opposite of
the key state. 6 lines from a PIC including the strobe.

--
Best regards

Tony

http://www.picnpoke.com
Email salesspamKILLspampicnpoke.com

1999\09\07@124739 by Andre Abelian

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No you can't
I do not think it is economical to reserve 16 I/O  for keypad.


Andre



> I have an hex keypad with 16 pins (one for each key) and 1 common.
> Can I use this type of keypad in a project that requires a 4x4 matrix
> keypad (8 lines/pins)(row/column selection)?
> How can I do that?
>

1999\09\24@055841 by bill

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No easy way to make it work with that project as-is, but could conceivably
read such a keypad with a 16c7x series pic using some resistors and an a/d
input.  Simultaneous keypresses would confuse it though, and false readings
would be possible when the voltage is changing, depending on what resistor
values are chosen and how much capacitance is present.  This would have
to be dealt with in software.  Not the prettiest solution, but it does have the
advantage of consuming only one pin on the pic.

> I have an hex keypad with 16 pins (one for each key) and 1 common.
> Can I use this type of keypad in a project that requires a 4x4 matrix
> keypad (8 lines/pins)(row/column selection)?
> How can I do that?

---
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                                       William Kitchen
                                       .....billKILLspamspam.....iglobal.net

The future is ours to create.

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