[51] How to interface ADC0808 with 8051 and LCD using assembly language

ijp · Dec 30, 2014

Hi I am really stuggling in displaying a random value,which i inputed manually in a port and then converted it to ASCII digit, on an LCD. The code doesn't give me any error when i simulate it, it just moves the cursor to the 3 positions i want to put the digits in, but does not show anything on the LCD. Here is my code:
Can anyone please tell me what am i missing?
Thank you. ;-)

Code ASM - [expand]
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LCD_data equ P2    ;LCD Data port
LCD_rs   equ P0.2  ;LCD Register Select
LCD_rw   equ P0.1  ;LCD Read/Write
LCD_en   equ P0.0  ;LCD Enable
RAM_ADDR EQU 40H
ASCI_RSULT EQU 50H
COUNT EQU 3
ORG 0000h ; power up and reset vector 
AJMP START 
ORG 0060h
 START: 
CONVERSION:
        MOV P0,#0FFH
        MOV P2,#0FFH                ;make the ports inputs by writing all 1's to it, PORT 2 IS USED FOR LCD ;DATA PINS
        CLR PSW.3
        CLR PSW.4                     ;select bank 0
   
        MOV A,#00000000b
        MOV P2,A                    ;PORT 2 is used for the LCD data pins. 
        MOV P0,#11110001b           ;PUTTING A RANDOM BINARY VALUE IN PORT0
          MOV R0,#RAM_ADDR     ;save DEC digits in these RAM locations
        MOV A,P0         ;read data from port 0
        MOV B,#10            ;B=0A hex(10dec)
        DIV AB               ;divide by 10
        MOV @R0,B            ;save lower digit
        INC R0
        MOV B,#10
        DIV AB               ;divide by 10 once more
        MOV @R0,B            ;save the next digit
        INC R0
        MOV @R0,A            ;save the last digit
;Now we convert the DEC digit to displayable ASCII digits
        MOV R0,#RAM_ADDR     ;address of DEC data
        MOV R1,#ASCI_RSULT   ;address of ascii data
        MOV R2,#3
        MOV R7,#3
BACK2: MOV A,@R0             ;get dec digit
       ORL A,#30H            ;make it an ASCII digit
       MOV @R1,A
       INC R0                ;next digit
       INC R1                ;next
       DJNZ R2,BACK2         ;repeat until the last one
 ;conversion done
INIT:
       
         clr  LCD_rs         ;Selected command register
         clr   LCD_rw         ;We are writing in instruction register
         setb  LCD_en         ;Enable H->L
         acall long_delay
         lcall LCD_init
         
          mov   LCD_data,#80H  ;position cursor
         clr   LCD_rs         ;Selected instruction register
         clr   LCD_en
         acall delay
         setb  LCD_en         ;Enable H->L
         acall delay
repeat:
          mov a,r0
         dec a
         mov r0,a
         mov a,@r0
         acall LCD_senddata
         djnz r7,repeat
STAY:    SJMP STAY
LCD_senddata:
         mov   LCD_data,A    ;Move the command to LCD port
         setb  LCD_rs        ;Selected data register
         clr   LCD_en
         acall delay
         setb  LCD_en         ;Enable H->L
         acall delay
         ret        
 LCD_init:
         mov   LCD_data,#0FH  ;Display on, Curson blinking command
         clr   LCD_rs         ;Selected instruction register
         clr   LCD_en
         acall delay
         setb  LCD_en         ;Enable H->L
         acall delay
         mov   LCD_data,#38H  ;Function Set 2-line mode (even for 16x1!)
         clr   LCD_rs         ;Selected instruction register
         clr   LCD_en
         acall delay
         setb  LCD_en         ;Enable H->L
         acall delay
         ret
delay:
    mov  r2, #01h
wait_0:
   mov  r3, #0FFh   ;reg2 and reg3
wait_1:
   djnz r3, wait_1
   djnz r2, wait_0
   ret
long_delay:
   mov  r2, #1fh   ;initialise counters
wait_2:
   mov  r3, #0ffh   ;reg2 and reg3
wait_3:
   mov  r4, #0ffh   ;reg2 and reg3
wait_4:
   djnz r4, wait_4
   djnz r3, wait_3
   djnz r2, wait_2
   ret       
END

milan.rajik · Dec 30, 2014

https://www.dnatechindia.com/Tutorial/8051-Tutorial/Interfacing-ADC0808-To-8051.html

ijp · Dec 31, 2014

not really. At the moment I am not using an ADC, I am just putting a random value for example P0 has 11110001, and I converted this to ascii -241, stored this value in RAM location 42h,41h and 40h respectively and I am trying to display this taking from the RAM to the LCD screen, but it does not display anything on the screen,however the curser position is moving in the place where i want to display the digits. But no digit is displayed.
Can you please have a look at the code, i really need to get this solved as soon as possible

thank you

milan.rajik · Dec 31, 2014

You are making P2 input type. You should make it output type by clearing P2 or writing 0x00 to P2 initially as it is used for LCD data.

Code C - [expand]
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MOV P2,#0FFH

P0 is used for LCD Control. Does the P0 has pull-up resistors ?

Strobing the LCD is making the EN pin high say for 100 us and then making it low. You are doing the reverse. You are making it low and then high.

Read the book "8051 Microcontroller and Embedded System using Assembly and C" by Muhammad Ali Mazidi. It has lcd 8 bit asm and c example codes.

LCD initialization routine is sending commands 0x38, 0x0E, 0x01, 0x06. Then you send row and coloum command like 0x80 and then send lcd data. You use RS bit to decide whether you are sending command or data. You place data or command on P2 and then make en pin high for 100 us and then low.

Debasis Swain · Dec 31, 2014

Hi,Dear
You are just making some mistakes, so i am editing your code.
so, pls check the following

Code ASM - [expand]
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LCD_data equ P2    ;LCD Data port
LCD_rs   equ P0.2  ;LCD Register Select
LCD_rw   equ P0.1  ;LCD Read/Write
LCD_en   equ P0.0  ;LCD Enable
RAM_ADDR EQU 40H
ASCI_RSULT EQU 50H
COUNT EQU 3
ORG 0000h ; power up and reset vector 
SJMP START 
ORG 0060h
 START: 
CONVERSION:
        MOV P0,#0FFH
        MOV P2,#0FFH                ;make the ports inputs by writing all 1's to it, PORT 2 IS USED FOR LCD ;DATA PINS
        CLR PSW.3
        CLR PSW.4                     ;select bank 0
   
        MOV A,#00000000b
        MOV P2,A                    ;PORT 2 is used for the LCD data pins. 
        MOV P0,#11110001b           ;PUTTING A RANDOM BINARY VALUE IN PORT0
          MOV R0,#RAM_ADDR     ;save DEC digits in these RAM locations
        MOV A,P0         ;read data from port 0
        MOV B,#10            ;B=0A hex(10dec)
        DIV AB               ;divide by 10
        MOV @R0,B            ;save lower digit
        INC R0
        MOV B,#10
        DIV AB               ;divide by 10 once more
        MOV @R0,B            ;save the next digit
        INC R0
        MOV @R0,A            ;save the last digit
;Now we convert the DEC digit to displayable ASCII digits
        MOV R0,#RAM_ADDR     ;address of DEC data
        MOV R1,#ASCI_RSULT   ;address of ascii data
        MOV R2,#3
        MOV R7,#3
        
BACK2: clr      a
          MOV A,@R0             ;get dec digit
       ORL A,#30H            ;make it an ASCII digit
       MOV @R1,A
       INC R0                ;next digit
       INC R1                ;next
       DJNZ R2,BACK2         ;repeat until the last one
 ;conversion done
INIT:
       
         ;clr  LCD_rs         ;Selected command register
         clr   LCD_rw         ;We are writing in instruction register
         ;setb  LCD_en         ;Enable H->L
         acall long_delay
         lcall LCD_init
         
          mov   LCD_data,#80H  ;position cursor
         clr   LCD_rs         ;Selected instruction register
         setb   LCD_en
         acall delay
         clr  LCD_en         ;Enable H->L
         acall delay
repeat: clr     a
                dec     r1
          ;mov a,r1
         ;dec a
         ;mov r0,a
         mov a,@r1
         acall LCD_senddata
         djnz r7,repeat
STAY:    SJMP STAY
LCD_senddata:
         mov   LCD_data,A    ;Move the command to LCD port
         setb  LCD_rs        ;Selected data register
         SETB   LCD_en
         acall delay
                CLR     LCD_en
                  ;Enable H->L
         ;acall delay
         ret        
 LCD_init:
         mov   LCD_data,#0EH  ;Display on, Curson blinking command
         clr   LCD_rs         ;Selected instruction register
         setb   LCD_en
         acall delay
         clr  LCD_en         ;Enable H->L
         acall delay
         mov   LCD_data,#38H  ;Function Set 2-line mode (even for 16x1!)
         clr   LCD_rs         ;Selected instruction register
         setb   LCD_en
         acall delay
         clr  LCD_en         ;Enable H->L
         acall delay
                
         mov   LCD_data,#06H  ;Function Set 2-line mode (even for 16x1!)
         clr   LCD_rs         ;Selected instruction register
         setb   LCD_en
         acall delay
         clr  LCD_en         ;Enable H->L
         acall delay
         ret
delay:
    mov  r2, #01h
wait_0:
   mov  r3, #0FFh   ;reg2 and reg3
wait_1:
   djnz r3, wait_1
   djnz r2, wait_0
   ret
long_delay:
   mov  r2, #1fh   ;initialise counters
wait_2:
   mov  r3, #0ffh   ;reg2 and reg3
wait_3:
   mov  r4, #0ffh   ;reg2 and reg3
wait_4:
   djnz r4, wait_4
   djnz r3, wait_3
   djnz r2, wait_2
   ret       
END

ijp · Dec 31, 2014

Thanks a lot for the code but when i run the code, it gives me- 000 on the LCD screen whereas i should be getting 241 on the screem as P0 has 11110001 on it. Please can you post the correct code for me? thank you

- - - Updated - - -

Here is a code i wrote again but I still get 000 in the LCD screen instead of 241

can you please help fix it?

Code ASM - [expand]
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LCD_data equ P2    ;LCD Data port
LCD_rs   equ P3.7  ;LCD Register Select
LCD_rw   equ P3.6  ;LCD Read/Write
LCD_en   equ P3.5  ;LCD Enable
RAM_ADDR EQU 40H
ASCI_RSULT EQU 50H
COUNT EQU 3
ORG 0000h ; power up and reset vector 
AJMP START 
ORG 0060h
 START: 
CONVERSION:
        MOV P0,#0FFH
        MOV P2,#0FFH                ;make the ports inputs by writing all 1's to it, PORT 2 IS USED FOR LCD ;DATA PINS
        CLR PSW.3
        CLR PSW.4                     ;select bank 0
   
        MOV A,#00000000b
        MOV P2,A                    ;PORT 2 is used for the LCD data pins. 
        MOV P0,#11110001b           ;PUTTING A RANDOM BINARY VALUE IN PORT0
          MOV R0,#RAM_ADDR     ;save DEC digits in these RAM locations
        MOV A,P0         ;read data from port 0
        MOV B,#10            ;B=0A hex(10dec)
        DIV AB               ;divide by 10
        MOV @R0,B            ;save lower digit
        INC R0
        MOV B,#10
        DIV AB               ;divide by 10 once more
        MOV @R0,B            ;save the next digit
        INC R0
        MOV @R0,A            ;save the last digit
;Now we convert the DEC digit to displayable ASCII digits
        MOV R0,#RAM_ADDR     ;address of DEC data
        MOV R1,#ASCI_RSULT   ;address of ascii data
        MOV R2,#3
        MOV R7,#3
BACK2: MOV A,@R0             ;get dec digit
       ORL A,#30H            ;make it an ASCII digit
       MOV @R1,A
       INC R0                ;next digit
       INC R1                ;next
       DJNZ R2,BACK2         ;repeat until the last one
 ;conversion done
INIT:
       
        
         clr   LCD_rw         ;We are writing in instruction register
         acall long_delay
         lcall LCD_init
         
          mov   LCD_data,#80H  ;position cursor
         clr   LCD_rs         ;Selected instruction register
         setb   LCD_en
         acall delay
         clr  LCD_en         ;Enable H->L
         acall delay
         
repeat:   clr a
          
         dec r0
         mov a,@r0
         acall LCD_senddata
         djnz r7,repeat
STAY:    SJMP STAY
LCD_senddata:
         mov   LCD_data,a    ;Move the command to LCD port
         setb  LCD_rs        ;Selected data register
         setb   LCD_en
         acall delay
         clr  LCD_en         ;Enable H->L
         acall delay
         ret        
 LCD_init:
         mov   LCD_data,#0FH  ;Display on, Curson blinking command
         clr   LCD_rs         ;Selected instruction register
         setb   LCD_en
         acall delay
         clr  LCD_en         ;Enable H->L
         acall delay
         mov   LCD_data,#38H  ;Function Set 2-line mode (even for 16x1!)
         clr   LCD_rs         ;Selected instruction register
         setb   LCD_en
         acall delay
         clr  LCD_en         ;Enable H->L
         acall delay
          mov   LCD_data,#06H  
         clr   LCD_rs         ;Selected instruction register
         setb   LCD_en
         acall delay
         clr  LCD_en         ;Enable H->L
         acall delay
         
         ret
delay:
    mov  r2, #50
wait_0:
   mov  r3, #0FFh   ;reg2 and reg3
wait_1:
   djnz r3, wait_1
   djnz r2, wait_0
   ret
long_delay:
    mov  r2, #01h   ;initialise counters
 wait_2:
    mov  r3, #07fh   ;reg2 and reg3
 wait_3:
    mov  r4, #0ffh   ;reg2 and reg3
 wait_4:
    djnz r4, wait_4
    djnz r3, wait_3
    djnz r2, wait_2
    ret
END

ud23 · Jan 1, 2015

Code:

repeat:   clr a
          
         dec r0
         mov a,@r0
         acall LCD_senddata
         djnz r7,repeat
STAY:    SJMP STAY

I guess you are storing the ASCII value in R1 and reading the data from R0 and displaying it on LCD

Debasis Swain · Jan 1, 2015

You are just making some error in place of displayed the ascii value, you are using R0 in place of R1 so, check it, also remember that clear the accumulator in place of using the A at pointer. I'm giving the code in before reply so, try to using that code for output

ijp · Jan 1, 2015

Hi everyone,
i have fixed the code by clearing the accumulator before using it as a pointer and also using R1 to read the data from and displaying it, but i am getting 000 in the LCD display instead of 241, i have also debugged the code and checked that R1 HAS, 2 4 1 in it when i use
this code part, i dnt know why i am still not getting it

I need more help..
CODE:

Code ASM - [expand]
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repeat:   clr a
          
         dec r1
         mov a,@r1
         acall LCD_senddata
         djnz r7,repeat
STAY:    SJMP STAY

ud23 · Jan 1, 2015

Code:

repeat: clr     a
          dec     r1
         
         mov a,@r1
         acall LCD_senddata
         djnz r7,repeat
          STAY:    SJMP STAY
 LCD_senddata:
         mov   LCD_data,A    ;Move the command to LCD port
         setb  LCD_rs        ;Selected data register
         SETB   LCD_en
         acall delay
         CLR     LCD_en   ;Enable H->L
        acall delay
         ret

as answered earlier

ijp · Jan 1, 2015

Yes, I did the same thing as you wrote on the code above, but I am still not getting the right result. If you look at my full code in my previous post, you can see that I have already done the correction but i am still not getting the result.

ud23 · Jan 1, 2015

zip your full code here i look at it or you can use this working lcd referance codes below.

https://www.projectsof8051.com/downloads/asmcodes/8051-liquid-crystal-display.html
https://www.pjrc.com/tech/8051/board5/lcd_example.asm

ijp · Jan 1, 2015

Here is my full code, it just displays 000 in the lcd. Please compile it and help me out in finding the mistake.
CODE:

Code:

LCD_data equ P2    ;LCD Data port
LCD_rs   equ P3.7  ;LCD Register Select
LCD_rw   equ P3.6  ;LCD Read/Write
LCD_en   equ P3.5  ;LCD Enable
RAM_ADDR EQU 40H
ASCI_RSULT EQU 50H
COUNT EQU 3
ORG 0000h ; power up and reset vector 
AJMP START 
ORG 0060h
 START: 
CONVERSION:
        MOV P0,#0FFH
        MOV P2,#0FFH                ;make the ports inputs by writing all 1's to it, PORT 2 IS USED FOR LCD ;DATA PINS
        CLR PSW.3
        CLR PSW.4                     ;select bank 0
   
        MOV A,#00000000b
        MOV P2,A                    ;PORT 2 is used for the LCD data pins. 
        MOV P0,#11110001b           ;PUTTING A RANDOM BINARY VALUE IN PORT0
          MOV R0,#RAM_ADDR     ;save DEC digits in these RAM locations
        MOV A,P0         ;read data from port 0
        MOV B,#10            ;B=0A hex(10dec)
        DIV AB               ;divide by 10
        MOV @R0,B            ;save lower digit
        INC R0
        MOV B,#10
        DIV AB               ;divide by 10 once more
        MOV @R0,B            ;save the next digit
        INC R0
        MOV @R0,A            ;save the last digit
;Now we convert the DEC digit to displayable ASCII digits
        MOV R0,#RAM_ADDR     ;address of DEC data
        MOV R1,#ASCI_RSULT   ;address of ascii data
        MOV R2,#3
        MOV R7,#3
BACK2: MOV A,@R0             ;get dec digit
       ORL A,#30H            ;make it an ASCII digit
       MOV @R1,A
       INC R0                ;next digit
       INC R1                ;next
       DJNZ R2,BACK2         ;repeat until the last one
 ;conversion done
INIT:
       
        
         clr   LCD_rw         ;We are writing in instruction register
         acall long_delay
         lcall LCD_init
         
          mov   LCD_data,#80H  ;position cursor
         clr   LCD_rs         ;Selected instruction register
         setb   LCD_en
         acall delay
         clr  LCD_en         ;Enable H->L
         acall delay
         
repeat:   clr a
          
         dec r1
         mov a,@r1
         acall LCD_senddata
         djnz r7,repeat
STAY:    SJMP STAY
LCD_senddata:
         mov   LCD_data,a    ;Move the command to LCD port
         setb  LCD_rs        ;Selected data register
         setb   LCD_en
         acall delay
         clr  LCD_en         ;Enable H->L
         acall delay
         ret        
 LCD_init:
         mov   LCD_data,#0FH  ;Display on, Curson blinking command
         clr   LCD_rs         ;Selected instruction register
         setb   LCD_en
         acall delay
         clr  LCD_en         ;Enable H->L
         acall delay
         mov   LCD_data,#38H  ;Function Set 2-line mode (even for 16x1!)
         clr   LCD_rs         ;Selected instruction register
         setb   LCD_en
         acall delay
         clr  LCD_en         ;Enable H->L
         acall delay
          mov   LCD_data,#06H  
         clr   LCD_rs         ;Selected instruction register
         setb   LCD_en
         acall delay
         clr  LCD_en         ;Enable H->L
         acall delay
         
         ret
delay:
    mov  r2, #50
wait_0:
   mov  r3, #0FFh   ;reg2 and reg3
wait_1:
   djnz r3, wait_1
   djnz r2, wait_0
   ret
long_delay:
    mov  r2, #01h   ;initialise counters
 wait_2:
    mov  r3, #07fh   ;reg2 and reg3
 wait_3:
    mov  r4, #0ffh   ;reg2 and reg3
 wait_4:
    djnz r4, wait_4
    djnz r3, wait_3
    djnz r2, wait_2
    ret
END

Debasis Swain · Jan 2, 2015

I have already test the code which that i have post before. So, test your code which is edited my me and reply

- - - Updated - - -

just test reply-5, and reply

ijp · Jan 2, 2015

I have tested the code you edited for me in the reply 5, but that code does not work. It is also giving me 000 on the LCD screen

Can you please have a look and test the code again, because it actually does not work for me. I am really tensed.
Thank you.

ud23 · Jan 3, 2015

Code ASM - [expand]
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;====================================================================
; Main.asm file generated by New Project wizard
;
; Created:   Sat Jan 3 2015
; Processor: AT89C51
; Compiler:  ASEM-51 (Proteus)
;====================================================================
 
$NOMOD51
$INCLUDE (8051.MCU)
 
 
 
    RS EQU P3.7
        EN EQU P3.6
        ;WR EQU P2.5
 
        ORG 0000H
        LJMP MAIN
 
MSG1:   DB 'lcd display',0H
MSG2:   DB 'assembly level programing',0H
 
 
;********************
DELAY_SET:
;********************
        MOV R2,#5
L1:     MOV TH1,# HIGH(-50000)
        MOV TL1,# LOW(-50000)
        SETB TR1
        JNB TF1,$
        CLR TF1
        CLR TR1
        DJNZ R2,L1
        RET
 
 
 
;********************
DELAY:
;********************
        MOV TH0,# HIGH(-50000)
        MOV TL0,# LOW(-50000)
        SETB TR0
        JNB TF0,$
        CLR TF0
        CLR TR0
        RET
 
 
 
;********************
WRITE_CMD:
;********************
        CLR RS
        MOV P2,A
        SETB EN
        CLR EN
        LCALL DELAY
        RET
 
 
 
;********************
WRITE_CHAR:
;********************
        SETB RS
        MOV P2,A
        SETB EN
        CLR EN
        LCALL DELAY
        RET
 
 
 
;********************
INITIALIZE_LCD:
;********************
        MOV A,#38H              ;FUNCTION SET
        LCALL WRITE_CMD
        MOV A,#0CH              ;DISPLAY ON/OFF AND CURSOR
        LCALL WRITE_CMD
        MOV A,#06H              ;CHARACTER ENTRY MODE
        LCALL WRITE_CMD
        RET
 
 
;********************
GOTO_ADDRESS:
;********************
        ADD A,#80H
        LCALL WRITE_CMD
        RET
 
        
;********************
WRITE_STRING:
;********************
        MOV R1,#0
RPT:    MOV A,R1
        MOVC A,@A+DPTR
        JZ EXIT
        LCALL WRITE_CHAR
        INC R1
        LJMP RPT
EXIT:   RET
 
 
 
;********************
CLEAR_LCD:
;********************
        MOV A,#01H
        LCALL WRITE_CMD
        RET
 
 
 
;********************
MAIN:
;********************
        MOV TMOD,#11H
        LCALL INITIALIZE_LCD
       
       
L2:     
   
     mov     a, #250        ; value to convert
     acall   hextoascii      ; convert value
        
 
        MOV A,#00H
        LCALL GOTO_ADDRESS
        MOV a,r0
    LCALL WRITE_CHAR
        ;LCALL DELAY_SET
         MOV A,#01H
        LCALL GOTO_ADDRESS
        MOV a,r1
    LCALL WRITE_CHAR
        ;LCALL DELAY_SET
         MOV A,#02H
        LCALL GOTO_ADDRESS
        MOV a,r2
    LCALL WRITE_CHAR
        LCALL DELAY_SET
        
LJMP L2
 
hextoascii:
 
mov r0,#30h
mov r1,#30h
mov r2,#30h
        
 
clr c
mov b,#100
div ab
orl a,r0
mov r0,a
clr c   
mov a,b
mov b,#10
div ab
orl a,r1
mov r1,a        
mov a,b
orl a,r2
mov r2,a
        
ret
        
        
END

Hello i have tested your code and got same result 000 as u mentioned in your early post and after debugging I think your ram read value is wrong or your code not storing the value in RAM i guess due to less time i just build the code display random value in lcd attached here you can see and add your new RAM value logic and test this.I will update on RAM value soon when i will back.

ud23 · Jan 3, 2015

https://what-when-how.com/8051-microcontroller/8051-data-memory-space/

you can look above link for reference

Debasis Swain · Jan 3, 2015

I have already test the code with hardware and getting the output.So, pls check the hardware connection what you are use.

ijp · Jan 3, 2015

So are you saying that my code that i posted in my previous post 15, is correct? Because I think my ram address is correct and R1 is storing the right values. Please confirm me again if my code posted in post 15 is working? I still get 000 on lcd

Debasis Swain · Jan 4, 2015

just one thing do that,just copy my reply-5 code don't change any thing and according to that code connect your rs,rw,and en pins with lcd without your adc interface, and reply

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