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Author Topic: Keypad to Decimal Decoder  (Read 1203 times)
NT2F
Member

Posts: 7




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« on: December 16, 2010, 09:25:54 AM »

I am looking for a way to take the simple output from a keypad matrix and convert it to decimal. Don't mean to be obvious but I'm not sure I can put it into words properly.

The keypad output is derived from:

    1        2         3   -  Row 1
   4        5         6   -  Row 2
   7        8         9   -  Row 3
   *        0         #   -  Row 4
Col-1   Col-2   Col-3

When the "2" button is pressed then Col-2 and Row-1 are "ON" so this would give me a binary output that might look like:

   0         1         0         1          0          0          0
Col-1   Col-2   Col-3   Row-1   Row-2   Row-3   Row-4

So what I want to do is take the output from, for example, a 3x4 keypad and activate one of 12 outputs depending on the specific key pressed.

I suspect the best approach is to use a BCD-to-Digital decoder, but since the keypad output is not really BCD then I'm at a loss of how to proceed.

I did this logic stuff - truth tables and circuit design - over 30 years ago (has it really been that long?) but since then my career has taken me in other directions.

I suspect this is an easy question for some of you out there. As they say, "Use It or Loose It," and I have definitely lost it.

Any thoughts would be greatly appreciated.

73 - Jiim/NT2F

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WB6RXG
Member

Posts: 73




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« Reply #1 on: December 16, 2010, 02:06:33 PM »

Take a look at a 74922.  I think it's exactly what you are looking for.

73,
Stuart
WB6RXG
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WB6RXG
Member

Posts: 73




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« Reply #2 on: December 16, 2010, 02:10:05 PM »

I forgot to add that it's output is BCD which you can then put through a BCD to Decimal decoder.

73,
Stuart
WB6RXG
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NT2F
Member

Posts: 7




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« Reply #3 on: December 16, 2010, 03:17:50 PM »

Stuart

That's It!

Many thanks my friend and 73.

Jim/NT2F
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