4X4 keypad read

Brian_B · 2007-09-23 14:24

Hi all,
·I'm trying to read from a 4X4 keypad , it apears that the out pins are floating . Should I be using pull up or pull down resistors on the outputs ! If so what value ?

▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
Thank's Brian

www.truckwiz.com

·"Imagination is more important than knowledge..." ·· Albert Einstein

http://www.diycalculator.com/subroutines.shtml· My favorite website ( Bet you can't guess why)

deSilva · 2007-09-23 14:44

Brian Beckius said...
Should I be using pull up or pull down resistors on the outputs ! If so what value ?

(1) Hmmm, all the world takes 10k - so you should also... Funny question...
(2) up or down - well this depends on the active state of your key presses... That's something only you can know!
(3) Your code

       if ina[noparse][[/noparse]12] == 1
         number := 10 + index
       if ina[noparse][[/noparse]13] == 1
         number := 20 + index
       if ina[noparse][[/noparse]14] == 1
        number := 30 + index
       if ina[noparse][[/noparse]15] == 1
        number := 40 + index

can be simplified to

  IF INA [noparse][[/noparse]15..12]
     number := INA[noparse][[/noparse]15..12]*10 + index

Skogsgurra · 2007-09-23 14:50

Hello!

Did you really mean to say "out pins are floating"?

If that is so, you may have to look at the dira register and set output bits high.

(No, I didn't check your code. I am sure deSilva did)

▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔

Brian_B · 2007-09-23 15:03

I'm using 4 outputs to select the row of 4 keys . The program makes one output high and then checks to see if a key is pressed , Then it makes the next output high and checks the keys again . Rigth now when I run the program all the leds randomly go off and on with no keys being pressed.

▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
Thank's Brian

www.truckwiz.com

·"Imagination is more important than knowledge..." ·· Albert Einstein

http://www.diycalculator.com/subroutines.shtml· My favorite website ( Bet you can't guess why)

Skogsgurra · 2007-09-23 15:41

OK, a multiplexed keyboard. I asked if it is the output pins you were referring to. You do not need any pull-ups (or -downs) on the Prop outputs. They are not open collector.

▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔

Lawson · 2007-09-23 16:14

Do you have a pull-down resistor on the input pins of the Propeller? (needs to be a pull down 'cause the rows are driven high) If you don't have something like a pull-down resistor to define the default (off) state of an input it will float to some random value.

my log($1) cents,
Marty

▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
Lunch cures all problems! have you had lunch?

deSilva · 2007-09-23 16:40

Well, before it becomes absolutely confusing here:

(A) Please connect 10k resistors from GND to pins 12 to 15 of your Propeller ("pull down")
(B) The code

      dira[noparse][[/noparse] 8..11]~~
...
  someloop
....
      outa[noparse][[/noparse] 8..11]~
      outa[noparse][[/noparse] index]~~

is no good at all for a simple matrix, as two pressed keys make a shortcut!
Do

     OUTA[noparse][[/noparse] 8..11] ~~
....
  some loop
....
      DIRA[noparse][[/noparse] 8..11]~
      DIRA[noparse][[/noparse] index]~~

instead.

Then it should work!

Skogsgurra · 2007-09-23 17:01

came to think of that old story about the oldest profession - the one that ends in "and who created chaos?"

▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔

Brian_B · 2007-09-23 18:31

Sorry for the confusion , I somtimes forget that you guys arn't sitting here looking over my shoulder . deSilva , Works perfect ! Thank's

▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
Thank's Brian

www.truckwiz.com

·"Imagination is more important than knowledge..." ·· Albert Einstein

http://www.diycalculator.com/subroutines.shtml· My favorite website ( Bet you can't guess why)

4X4 keypad read

Comments