How to sequentially read 4x4 keypads

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JaNi

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Hi

I have 4X4 keypad
can i connect it to port in such a way that
the key i pressed is calculated form the input and the output

e.g

input is R1 and out put is C1

if i or the nibles(R and C) i get 0001 which is equlat to
the binary of 1 and so on up to 16
 

Key Pad

sorry dear
i know these things.
i want that the bit pattern which i get
by applying simple operation on nibles or if
needed rearanging the order of the connections
is the same as that of perticular key and keys are form 1 to F.
 

Re: Key Pad

The 74C922 or 923 does just that. It scans the keyboard matrix and puts up a Data Valid signal when a key is pressed. You can use this data valid to create an interrupt on your MCU and read the key through 4-5 bits. So the only thing u need from the MCU is 4-5 portpins and an interrupt. Ive used this before and although the 74C923 aint cheap ($10) it does the job perfectly and makes your MCU program really easy and very stable. It SAVES time and then $10 aint allot IMHO.
 

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