Display Keypad Data to LED

In this lesson we are like to design, how to scan keypad 4 x 4, and then display it to LED.

Step 1st
Build the circuit as shown in figure 2.8.2. As you seen on figure 2.2.8. P3.0 trough P3.7 is connected to keypad 4 x 4 and to drive LEDs, it's connected to P2.0 trough P2.7.

Step 2nd
In this step, you must tipe the assembly program to scan your keypad data, we assume that you have already known the editor, we used RIDE-51 to edit the program. ( Download File : exp281.zip )

;In this lesson we'll scan keypad and get data out to LED
;and convert it into binary data
row1 bit P2.4
row2 bit P2.5
row3 bit P2.6
row4 bit P2.7
col1 bit P2.0
col2 bit P2.1
col3 bit P2.2
col4 bit P2.3
;
keydata   equ 70h
keybounc  equ 71h
keyport   equ P2
     org 0h
start: call keypad4x4    ;calling subroutine keypad4x4
     Mov A,keydata     ;A = keydata
     Cjne A,#0FFh,send ;
     sjmp start        ;LOOPING FOREVER
send:  CPL A             ;A = NOT A
     Mov P0,A          ;P0 = A
     Sjmp start        ;LOOPING FOREVER PART 2
;
delay: mov R0,#0
delay1:mov R2,#50
     djnz R2,$
     djnz R0,delay1
     ret
;
;====================================
; subroutine scan keypad 4x4
;====================================
Keypad4x4:
     mov keybounc,#50    ;keybounc = 50        
     mov keyport,#0FFh   ;keyport=P2= FF
     clr col1            ;col1= P3.0 = 0
Detect:jb row1,key1        ;jump to key1 if row1=1
     djnz keybounc,Detect
     mov keydata,#00h    ;Keydata =00h
     ret
;
key1: jb row2,key2         ;jump to Key2 if row2=1
    djnz keybounc,key1
    mov keydata,#04h     ;Keydata = 04h
    ret
;
key2: jb row3,key3         ; idem
    djnz keybounc,key2
    mov keydata,#08h
    ret
;
key3: jb row4,key4         ; idem
    djnz keybounc,key3
    mov keydata,#0Ch
    ret
;
key4: setb col1
    clr col2
    jb row1,key5
    djnz keybounc,key4
    mov keydata,#01h
    ret
;
key5: jb row2,key6
    djnz keybounc,key5
    mov keydata,#05h
    ret
;
key6: jb row3,key7
    djnz keybounc,key6
    mov keydata,#09h
    ret
;
key7: jb row4,key8
    djnz keybounc,key7
    mov keydata,#0Dh
    ret
;
key8: setb col2
    clr col3
    jb row1,key9
    djnz keybounc,key8
    mov keydata,#02h
    ret
;
key9: jb row2,keyA
    djnz keybounc,key9
    mov keydata,#06h
    ret
;
keyA: jb row3,keyB
    djnz keybounc,keyA
    mov keydata,#0Ah
    ret
;
keyB: jb row4,keyC
    djnz keybounc,keyB
    mov keydata,#0Eh
    ret
;
keyC: setb col3
    clr col4
    jb row1,keyD
    djnz keybounc,keyC
    mov keydata,#03h
    ret
;
keyD: jb row2,keyE
    djnz keybounc,keyD
    mov keydata,#07h
    ret
;
keyE: jb row3,keyF
    djnz keybounc,keyE
    mov keydata,#0Bh
    ret
;
keyF: jb row4,Nokey
    djnz keybounc,keyF
    mov keydata,#0Fh
    ret
Nokey:mov keydata,#0FFh  
    ret
;================================
;The end of Keypad 4x4 subroutine
;================================
end

Step 3rd
Safe your assembly program above, and name it with key1.asm (for example) Compile the program that you have been save by using RIDE-51, see the software instruction.


Step 4th
Download your hex file ( key1.hex ) into the microcontroller by using Microcontroller Laros ATMEL ISP software, see the instruction.After download this hex file you'll see the action of Keypad 4 x 4( of course if your cable connection and your program are corrected )