2.2.2. Running LED Right or Left when you’ re push the button

In this lesson, we will command the LED to run right or left by swichting the button, for example run the LED to the right when pushing swicht on P2.0 and run the LED to the left when pushing swicht on P2.1.

Figure 2.2.2. Diagram Skematik Input Data

Step 1st
Build the circuit as shown in figure 2.2.2. As you seen on figure 2.2.2. P2.0 trough P2.7 is connected to swicht push button each and LED’s Katode is connected to P0.0 trough P0.7. Remember, that all we want to do with this lesson is make a LED start running to the left or right, by pushing the button P2.0 or P2.1.

Step 2nd
In this step, you must tipe the assembly program to make your LED on when you push the swicht, we assume that you have already known the editor, we used MIDE-51 to edit the program. ( Download File : exp222.zip )

        org 0h
CekP20: JB P2.0,CekP21 ; checking P2.0 while get push
call RLeft     ; if so, call Rotate Left subrutine
sjmp CekP20    ; jump forever to CekP20 
CekP21: JB P2.1,CekP20 ; checking P2.1 while get push
call RRight    ; if so, call Rotate Right
sjmp CekP20    ; jump forever to CekP2.0
;===============================================        
;this subroutine is used to move LED to the left.
;================================================
RLeft:  mov A,#11111110b;send data to Acc
RLeft1: mov P0,A        ;send data to P0
call delay      ;call delay time
JB P2.0,RLeft2  ;checking P2.0 while get push
sjmp EndRLeft   ;if so, finish Rotate Left
RLeft2: RL A
sjmp RLeft1
EndRLeft:
ret

;=================================================        
;this subroutine is used to move LED to the right.
;=================================================
RRight: mov A,#01111111b
RRight1:mov P0,A
call delay
JB P2.0,RRight2
sjmp EndRRight
RRight2:RL A
sjmp RRight1
EndRRight:
ret
;=============================================
;subroutine delay created to rise delay time
;=============================================
delay: mov R1,#255
del1:  mov R2,#255
del2:  djnz R2,del2
djnz R1,del1
ret
end

Step 3rd
Safe your assembly program above, and name it with SW2.asm (for example) Compile the program that you have been save by using MIDE-51, see the software instruction.

Step 4th
Download your hex file ( SW2.hex ) into the microcontroller by using Microcontroller ATMEL ISP software, see the instruction.After download this hex file you’ll see the action of the LED ( of course if your cable connection and your program are corrected ).