4×4 keypad with 8255

[Nicolai]

Hi guys, 

I'm new to this forum.

I am currently doing my final year school project and i'm finding a difficulty with interfacing a 4×4 matrix keypad with and 8255 port expander (using port C) and all is connected to an 8051 microcontroller. 

I'm using C language and everything is working on a simulator (Proteus) but on the hardware side i'm only able to write text on an LCD (ex: Enter Value:) but not from the keypad.

Can anyone help me out pls? 
Any tips and ideas on what to look out for, pull up/down resistors etc etc

Thanks.

[boy2013]

Maybe I can help you Hi can you email me the project
Email me [email protected]

see you later..

[AJISH ALFRED]

Hi Nicolai,

Ya, that might be due to the absence of pullup/pulldown resistors. Could you please post your circuit also. Also tell me whether you are checking for a high value or low value to detect a key pressed. 

[Author]

Posts