Display Keypad 4 x 4 with LCD Character 2 x16

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 2x16 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 )