Interrupt driven keypad circuit design idea

mkr · Joined: 08 Aug 2006 Posts: 49

Hello Everybody,
I am designing a keypad detection circuit. The keypad is 4X4 matrix. 4 rows and 4 coloumn are
connected to the MCU (dsPIC30F6014a) by a typical diode and resistor circuit. I want to use interrupt to detect
any key press event so that the software does not need to scan the keypad always.

I am planning to use an OR/AND gate to accept the key press and tie the gate output to the
external interrupt of the MCU. The gate should have 4 or 5 wide input.

Do any one know of an OR/AND gate with above spec. Is there an better idea then using an gate circuit.

Your suggestion greatly appreciated.
_________________
Thanks

mkr

treitmey · Joined: 23 Jan 2004 Posts: 1094 Location: Appleton,WI USA

I use this circuit. It works great. It has a cap(hardware) debounce.
OK, I cant post the link directly,... it won't come up

goto
http://www.edn.com
do a search for interrupt keypad.

MCS-51 interrupt keypad should be a pick.

Then look at the "pdf friendly" version at the top.
((because they broke the links to the schematic view))