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'LCD and Keypad at the same Port'
1998\03\26@173953 by Wolfgang SchŠdle

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Hello All !

Is it possible to connect an LCD (in 4bit mode) and an Keypad (4x4) at the
same Port of an PIC. If yes, how has the Hardware to be ??

Thanks a lot for answers :-)

                               spam_OUTschaedleTakeThisOuTspamswol.de
 \ olle /                .....schaedleKILLspamspam@spam@usa.net
   \/\/olfgang    DB6TE @ DB0CZ

1998\03\26@205427 by Adi

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Hi!

Yes and no... To drive the LCD you need to use a pin for enable. You
can't use that pin for scanning the keypad. So... Here's what I've
done:

LCD --> PIC --> Keypad
DB7     RB3     Row4
DB6     RB2     Row3
DB5     RB1     Row2
DB4     RB0     Row1
R/W     RB4     Col1
RS      RB5     Col2
       RB6     Col3
       RB7     Col4
E       RAx

As you can see I used one port and one additional pin for E... The
software initializes PortB all high and all outputs. When driving the
LCD display make sure to keep RB6 and RB7 high! For scanning the
keyboard I make RB0 to RB3 inputs and pull RB4 to RB7 low one after
the other to scan the keyboard. Oh ja, you need pull-ups on RB0 to
RB3 (either external or enable internal if 16F84) and you need diodes
in the lines connecting the keys to RB0 to RB3 to prevent
interference between the LCD and keys...

Hope this helps...

Regards,
Adi

{Quote hidden}

1998\03\27@084717 by WF AUTOMACAO

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=?iso-8859-1?Q?Wolfgang_Sch=E4dle?= wrote:
>
> Hello All !
>
> Is it possible to connect an LCD (in 4bit mode) and an Keypad (4x4) at the
> same Port of an PIC. If yes, how has the Hardware to be ??
>
> Thanks a lot for answers :-)
>
>                                 EraseMEschaedlespam_OUTspamTakeThisOuTswol.de
>   \ olle /                schaedlespamspam_OUTusa.net
>     \/\/olfgang    DB6TE @ DB0CZ

EVERYDAY PRATICAL ELECTRONICS MAGAZINE NOVEMBER/1997  PAGE 782

has a schematic using the LCD DATA BUS to connect as a KEYBOARD!

mIGUEL.

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