[SOLVED] [MOVED] 4x4 Keypad hardware problem

[Isuru Senarath]

HI all
I connected my keypad to AT89S52 as shown in below figure, but I did not get required output.
Out put at LCD will be something like this
If I press this sequence> I will get this
Keypad > LCD
1, 2, 3, A > 1, 2, 3, A
4, 5, 6, B > 1, 2, 3, A
7, 8, 9, C > 1, 2, 3, A
*, 0, #, D > 1, 2, 3, A

What is wrong with my connection?

 

[ud23]

Re: 4x4 Keypad hardware problem

**broken link removed**

i don't understand your connection by pic u attached see above link it surly help you to rectify your problem

Out put at LCD will be something like this
If I press this sequence> I will get this
Keypad > LCD
1, 2, 3, A > 1, 2, 3, A
4, 5, 6, B > 1, 2, 3, A
7, 8, 9, C > 1, 2, 3, A
*, 0, #, D > 1, 2, 3, A

what do you mean by this ?

 

[Isuru Senarath]

Re: 4x4 Keypad hardware problem

If I press 1 in keypad, LCD will display 1 correct
If I press 2 in keypad, LCD will display 2 ''
If I press 3 in keypad, LCD will display 3 ''
If I press A in keypad, LCD will display A ''

but
If I press 4 in keypad, LCD will display 1 incorrect
If I press 5 in keypad, LCD will display 2 ''
If I press 6 in keypad, LCD will display 3 ''
If I press B in keypad, LCD will display A ''

 

[Isuru Senarath]

Re: 4x4 Keypad hardware problem

This is my schematic diagram

 

[ud23]

Re: 4x4 Keypad hardware problem

This is my schematic diagramView attachment 75061

you are using port 0 so you need to have pull up resistor.
And if your getting in correct answer in lcd mean some wrong with your key pad scanning routine. i am assuming your code is working but have incorrect display. please post your code.

 

[Isuru Senarath]

Re: 4x4 Keypad hardware problem

See attachment. I attach protues file also.View attachment My program.rar

 

[praba_J]

Re: 4x4 Keypad hardware problem

i go through with your proteus file.. but it is working correctly.. for me the results are
1,2,3,A
4,5,6,B
7,8,9, (space)
Y,0,N,special char)
i think it's ok..

 

[rohitkhanna]

Re: 4x4 Keypad hardware problem

you are using port 0 so you need to have pull up resistor.
And if your getting in correct answer in lcd mean some wrong with your key pad scanning routine. i am assuming your code is working but have incorrect display. please post your code.

I agree. First thing to do is put in the pull-ups. Without that, your results will be ambigous.