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lcd and switch multiplexing with 18f452 portb

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zeroskj1988

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i am using pic18f452.inmy project,i have to multiplex LCD(jhd539,16X4) and switches. i am using lcd in 4 bit mode
i directly connected switch and data line of lcd to portb<1-4>.when am working with pgm there is random variations.my doubt is whether there is any problem in multiplexing directly. pls help me
thanks in advance
 

It would be better to see the schematic.
 

It is not advisable to connect datalines and keypad to same port pins directly.
 

zeroskj1988 said:
i am using pic18f452.inmy project,i have to multiplex LCD(jhd539,16X4) and switches. i am using lcd in 4 bit mode
i directly connected switch and data line of lcd to portb<1-4>.when am working with pgm there is random variations.my doubt is whether there is any problem in multiplexing directly. pls help me
thanks in advance
Click to expand...

You can easily connect the switches and LCD on the same lines. See the attached schematic. the pull up resistors are 4K7 and pull doen are 1K.

27_1312788180.gif


Cheers

Ravi
 
thank u sir
i using schematic similar to your,except the pull up resistor
but i am getting response that some keys pressed even if am not pressed it
 

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