Need guidance on 4x4 keypad interface

[jianhuachews]

Hi guys.

Ok i have been googling and looking up in the forums for days but i still am very unsure about keypad interfacing. I want to design a 4x4 keypad decoder in FPGA using vhdl, and then display it on the 7 segment led of my nexys 2 spartan 3e board.

When pressed, ie: 5, on the keypad, the 7 segment should show a 5.

I understand that a 4x4 keypad has 4 inputs and 4 outputs (row and column) but how do i go about scanning which keys are actually detected? I've seen this term called like "de-bounce" but i totally has no idea what it really does. Also, how do i know which 2 pins of the keypad are for which push buttons?

I'm really confused on what i should do. Do i need a block diagram to implement this so that it'll be easier for me to understand?

 

[sanju_]

hi
debounce ---> look tutorials Cosmiac - Debounce - Configurable Space Microsystems Innovations & Applications Center
7 segment ---> **broken link removed**
this only for reference
https://www.edaboard.com/threads/210619/

 

[bajgik]

interfacing keypad with microcontroller: **broken link removed**

 

[jianhuachews]

Lets say i have a row - R0,R1,R2,R3 and column - C0,C1,C2,C3 (to scan which keys are pressed) and i tie all the rows to high impedance, '1', while columns, i have it running using shift register (ie; 0111, 1011, 1101, 1110).

I was told that i will need a ring counter too but the thing is im lost, after reading up on ring counter. Ring counter works entirely like a shift register isn't it?

can anyone correct me if i'm wrong? anyone, enlighten me please....

--Edit with block diagram uploaded.






*YellowCircled - Column
*RedCircled - Ring Counter

 

[jianhuachews]

ok i supposed the ring counter in the block diagram are used for my 4-digit 7 segment. Does it sound right, anyone?