4x4 keypad interface using MM74C922N encoder

hey guys! i am building a security coded safe as a project for school, my problem is the output of the encoder, when i press 1 it gives a binary output of 0000,2=0001,3=0010,A=0011,4,5&6 are correct then B=0111 then the rest are a digit ahead. I am using a PIC16F873A.I need to display a three digit number on three seven segments(common anode) pic basic pro ,please help

Khullekani said:

hey guys! i am building a security coded safe as a project for school, my problem is the output of the encoder, when i press 1 it gives a binary output of 0000,2=0001,3=0010,A=0011,4,5&6 are correct then B=0111 then the rest are a digit ahead. I am using a PIC16F873A.I need to display a three digit number on three seven segments(common anode) pic basic pro ,please help

Click to expand...

hi,
The keypad for a 4*4 when using a 74C922 is connected do the A,B,C,D, binary code output is as shown in image #1.
Key '0' when pressed sets A,B,C,D low, the DAVL is set Low. Use the DAVL line to generate an Interrupt in the PIC, then read the A,B,C,D lines.

Image #2, shows OE pin of the 74C922 connected via an inverter from /DAVL.
If you are not multiplexing the ABCD pins, then the inverter is not required, just connect the OE pin high.

So for Key #0, its 0000 an key#1 its 0001...


NOTE: by OR'ing the ABCD code with 30h [0x30] you will have the ASCII value ie 30h ['0'] and 31h ['1'] for the example given

Is it any sample coding to free running of it? =)