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Display Keypad Data to LED

30 September 2008


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.
<!–
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google_ad_slot = “5263478057”;
google_ad_width = 180;
google_ad_height = 90;
//–>

<script type="text/javascript"
src=”http://pagead2.googlesyndication.com/pagead/show_ads.js”&gt;

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 )

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