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Display Keypad 4 x 4 with LCD Character 2 x16

30 September 2008


After doing lesson 2.8.1. you can see that how easy to scan keypad and read data out to LED. In this lesson it’s look like lesson 2.8.2. but the data will read out with LCD Character 2 x16.

Figure 2.8.3.Keypad Connection to Microcontroller

Step 1st
Build the circuit as shown in figure 2.8.3. As you seen on figure 2.8.2 P3.0 trough P3.7 is connected to keypad 4 x 4 and LCD Character 2×16 to read keypad data, connected to P0.0 trough P0.7., P2.0 and P2.1 connected to RS and EN each.

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 : exp282.zip)

;the following experiment is used to scan 
;keypad 4x4 and result of scan will be released
;to LCD Character
row1 bit P3.4
row2 bit P3.5
row3 bit P3.6
row4 bit P3.7
col1 bit P3.0
col2 bit P3.1
col3 bit P3.2
col4 bit P3.3
;
keydata equ 70h
keybounc equ 71h
keyport equ P3
org 0h
start: call keypad4x4 ;calling subroutine keypad4x4
Mov A,keydata ;A = keydata
Cjne A,#0FFh,WrLCD;
sjmp start ;LOOPING FOREVER PART 1
;
WrLCD: Mov R1,#80h ;Pick DDRAM 1st row and 1st col
call write_inst
Mov R1,A
call write_data ;write data
Sjmp start ;LOOPING FOREVER PART 2
;
Init_lcd:
mov r1,#00000001b ;Display clear
acall write_inst ;
mov r1,#00111000b ;Function set,
;Data 8 bit,2 line font 5x7
acall write_inst ;
mov r1,#00001100b ;Display on,
;cursor off,cursor blink off
acall write_inst
mov r1,#00000110b ;Entry mode, Set increment
acall write_inst
ret
;
Write_inst:
clr P2.0 ; RS = P2.0 = 0, write mode instruction
mov P0,R1 ; D7 s/d D0 = P0 = R1
setb P2.1 ; EN = 1 = P2.1
call delay; call delay time
clr P2.1 ; EN = 0 = P2.1
ret
;
Write_data:
setb P2.0 ; RS = P2.0 = 1, write mode data
mov P0,R1 ; D7 s/d D0 = P0 = R1
setb P2.1 ; EN = 1 = P2.1
call delay; call delay time
clr p2.1 ; EN = 0 = P2.1
ret
;
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 key2.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 ( key2.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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