Interfacing 16×2 LCD with 8051

admin May 22, 2017 32 Comments

LCD display is an inevitable part in almost all embedded projects and this article is about interfacing a 16×2 LCD with 8051 microcontroller. Many guys find it hard to interface LCD module with the 8051 but the fact is that if you learn it properly, its a very easy job and by knowing it you can easily design embedded projects like digital voltmeter / ammeter, digital clock, home automation displays, status indicator display, digital code locks, digital speedometer/ odometer, display for music players etc etc. Thoroughly going through this article will make you able to display any text (including the extended characters) on any part of the 16×2 display screen. In order to understand the interfacing first you have to know about the 16×2 LCD module.

16×2 LCD module.

16×2 LCD module is a very common type of LCD module that is used in 8051 based embedded projects. It consists of 16 rows and 2 columns of 5×7 or 5×8 LCD dot matrices. The module were are talking about here is type number JHD162A which is a very popular one . It is available in a 16 pin package with back light ,contrast adjustment function and each dot matrix has 5×8 dot resolution. The pin numbers, their name and corresponding functions are shown in the table  below.

Pin No: Name  Function
1 VSS This pin must be connected to the ground
2 VCC  Positive supply voltage pin (5V DC)
3 VEE Contrast adjustment
4 RS Register selection
5 R/W Read or write
6 E  Enable
7 DB0  Data
8 DB1  Data
9 DB2  Data
10 DB3  Data
11 DB4  Data
12 DB5  Data
13 DB6  Data
14 DB7  Data
15 LED+  Back light LED+
16 LED-  Back light LED-

VEE pin is meant for adjusting the contrast of the LCD display and the contrast can be adjusted by varying the voltage at this pin. This is done by connecting one end of a POT to the Vcc (5V), other end to the Ground and connecting the center terminal (wiper) of of the POT to the VEE pin. See the circuit diagram for better understanding.

The JHD162A has two built in registers namely data register and command register.  Data register is for placing the data to be displayed , and the command register is to place the commands. The 16×2 LCD module has a set of commands each meant for doing a particular job with the display. We will discuss in detail about the commands later. High logic at the RS pin will select the data register and  Low logic at the RS pin will select the command register. If we make the RS pin high and the put a data in the 8 bit data line (DB0 to DB7) , the LCD module will recognize it as a data to be displayed .  If we make RS pin low and put a data on the data line, the module will recognize it as a command.

R/W pin is meant for selecting between read and write modes. High level at this pin enables read mode and low level at this pin enables write mode.

E pin is for enabling the module. A high to low transition at this pin will enable the module.

DB0 to DB7 are the data pins. The data to be displayed and the command  instructions are  placed on these pins.

LED+ is the anode of the back light LED and this pin must be connected to Vcc through a suitable series current limiting resistor. LED- is the cathode of the back light LED and this pin must be connected to ground.

16×2 LCD module commands.

16×2 LCD module has a set of preset command instructions. Each command will make the module to do a particular task. The commonly used commands and their function are given in  the  table below.

Command                       Function
0F LCD ON, Cursor ON, Cursor blinking ON
01 Clear screen
02 Return home
04 Decrement cursor
06 Increment cursor
0E Display ON ,Cursor blinking OFF
80 Force cursor to the beginning of  1st line
C0 Force cursor to the beginning of 2nd line
38 Use 2 lines and 5×7 matrix
83 Cursor line 1 position 3
3C Activate second line
08 Display OFF, Cursor OFF
C1 Jump to second line, position1
OC Display ON, Cursor OFF
C1 Jump to second line, position1
C2 Jump to second line, position2

LCD initialization.

The steps that has to be done for initializing the LCD display is given below and these steps are common for almost all applications.

  • Send 38H to the 8 bit data line for initialization
  • Send 0FH for making LCD ON, cursor ON and cursor blinking ON.
  • Send 06H for incrementing cursor position.
  • Send 01H for clearing the display and return the cursor.

Sending data to the LCD.

The steps for sending data to the LCD module is given below. I have already said that the LCD module has pins namely RS, R/W and E. It is the logic state of these pins that make the module to determine whether a given data input  is a command or data to be displayed.

  • Make R/W low.
  • Make RS=0 if data byte is a command and make RS=1 if the data byte is a data to be displayed.
  • Place data byte on the data register.
  • Pulse E from high to low.
  • Repeat above steps for sending another data.

Circuit diagram.

interface LCD with 8051

Interfacing 16×2 LCD module to 8051

The circuit diagram given above shows how to interface a 16×2 LCD module with AT89S1 microcontroller. Capacitor C3, resistor R3 and push button switch S1 forms the reset circuitry. Ceramic capacitors C1,C2 and crystal X1 is related to the clock circuitry which produces the system clock frequency. P1.0 to P1.7 pins of the microcontroller is connected to the DB0 to DB7 pins of the module respectively and through this route the data goes to the LCD module.  P3.3, P3.4 and P3.5 are connected to the E, R/W, RS pins of the microcontroller and through this route the control signals are transffered to the LCD module. Resistor R1 limits the current through the back light LED and so do the back light intensity. POT R2 is used for adjusting the contrast of the display. Program for interfacing LCD to 8051 microcontroller is shown below.

Program.

MOV A,#38H // Use 2 lines and 5x7 matrix
ACALL CMND
MOV A,#0FH // LCD ON, cursor ON, cursor blinking ON
ACALL CMND
MOV A,#01H //Clear screen
ACALL CMND
MOV A,#06H //Increment cursor
ACALL CMND
MOV A,#82H //Cursor line one , position 2
ACALL CMND
MOV A,#3CH //Activate second line
ACALL CMND
MOV A,#49D
ACALL DISP
MOV A,#54D
ACALL DISP
MOV A,#88D
ACALL DISP
MOV A,#50D
ACALL DISP
MOV A,#32D
ACALL DISP
MOV A,#76D
ACALL DISP
MOV A,#67D
ACALL DISP
MOV A,#68D
ACALL DISP

MOV A,#0C1H //Jump to second line, position 1
ACALL CMND

MOV A,#67D
ACALL DISP
MOV A,#73D
ACALL DISP
MOV A,#82D
ACALL DISP
MOV A,#67D
ACALL DISP
MOV A,#85D
ACALL DISP
MOV A,#73D
ACALL DISP
MOV A,#84D
ACALL DISP
MOV A,#83D
ACALL DISP
MOV A,#84D
ACALL DISP
MOV A,#79D
ACALL DISP
MOV A,#68D
ACALL DISP
MOV A,#65D
ACALL DISP
MOV A,#89D
ACALL DISP

HERE: SJMP HERE

CMND: MOV P1,A
CLR P3.5
CLR P3.4
SETB P3.3
CLR P3.3
ACALL DELY
RET

DISP:MOV P1,A
SETB P3.5
CLR P3.4
SETB P3.3
CLR P3.3
ACALL DELY
RET

DELY: CLR P3.3
CLR P3.5
SETB P3.4
MOV P1,#0FFh
SETB P3.3
MOV A,P1
JB ACC.7,DELY

CLR P3.3
CLR P3.4
RET

END

Subroutine CMND sets the logic of the RS, R/W, E pins of the LCD module so that the module recognizes the input data ( given to DB0 to DB7) as a command.

Subroutine DISP sets the logic of the RS, R/W, E pins of the module so that the module recognizes the input data as a data to be displayed .

Interfacing LCD Module to 8051 in 4 Bit Mode (using only 4 pins of a port)

The microcontroller like 8051 has only limited number of  GPIO pins (GPIO – general purpose input output). So to design complex projects we need sufficient number of I/O pins . An LCD module can be interfaced with a microcontroller either in 8 bit mode (as seen above) or in 4 bit mode. 8 bit mode is the conventional mode which uses 8 data lines and RS, R/W, E pins for functioning. However 4 bit mode uses only 4 data lines along with the control pins. This will saves the number of GPIO pins needed for other purpose. 

Objectives

  • Interface an LCD with 8051 in 4 bit mode
  • Use a single port of the microcontroller for both data and control lines of the LCD.
Interfacing - 8051 to 16x2 LCD Module in 4 Bit Mode

LCD Module to 8051 – 4 Bit Mode

As shown in the circuit diagram, port 0 of the controller is used for interfacing it with LCD module. In 4 bit mode only 4 lines D4-D7, along with RS, R/W and E pins are used. This will save us 4 pins of our controller which we might employ it for other purpose. Here we only need to write to the LCD module. So the R/W pin can be ground it as shown in the schematic diagram. In this way the total number of pins can be reduced to 6. In 4 Bit mode the data bytes are split into two four bits and are transferred in the form of  a nibble. The data transmission to a LCD is performed by assigning logic states to the control pins RS and E. The reset circuit, oscillator circuit and power supply need to be provided for the proper working of the circuit.

Program – Interface LCD Module to 8051 – 4 Bit Mode

RS EQU P0.4
EN EQU P0.5
PORT EQU P0
U EQU 30H
L EQU 31H
ORG 000H

MOV DPTR,#INIT_COMMANDS
ACALL LCD_CMD
MOV DPTR,#LINE1
ACALL LCD_CMD
MOV DPTR,#TEXT1
ACALL LCD_DISP
MOV DPTR,#LINE2
ACALL LCD_CMD
MOV DPTR,#TEXT2
ACALL LCD_DISP
SJMP $


SPLITER: MOV L,A 
ANL L,#00FH 
SWAP A 
ANL A,#00FH 
MOV U,A 
RET

MOVE: ANL PORT,#0F0H 
ORL PORT,A
SETB EN 
ACALL DELAY 
CLR EN 
ACALL DELAY 
RET


LCD_CMD: CLR A
MOVC A,@A+DPTR
JZ EXIT2
INC DPTR 
CLR RS
ACALL SPLITER
MOV A,U
ACALL MOVE
MOV A,L
ACALL MOVE
SJMP LCD_CMD 
EXIT2: RET 
 
 
 
LCD_DATA: SETB RS
ACALL SPLITER
MOV A,U
ACALL MOVE
MOV A,L
ACALL MOVE 
RET

LCD_DISP: CLR A
MOVC A,@A+DPTR
JZ EXIT1
INC DPTR 
ACALL LCD_DATA 
SJMP LCD_DISP 
EXIT1: RET 
 
 


DELAY: MOV R7, #10H
L2: MOV R6,#0FH
L1: DJNZ R6, L1
DJNZ R7, L2
RET

INIT_COMMANDS: DB 20H,28H,0CH,01H,06H,80H,0 
LINE1: DB 01H,06H,06H,80H,0
LINE2: DB 0C0H,0 
CLEAR: DB 01H,0

TEXT1: DB " CircuitsToday ",0 
TEXT2: DB "4bit Using 1Port",0

END

Important aspects of the program

        The programming part is done in assembly language instead of embedded C. As mentioned earlier the 8 bit data is break into two 4 bit data and send to LCD. A subroutine called “SPLITTER” is used in the program  for  slicing 8 bit data into nibbles. It uses two memory location ‘U’ and ‘L’  for storing the upper and lower nibbles. The subroutine named “MOVE” is used to put the upper and lower nibbles into the data pins of the LCD by making a high to low pulse at the E pin of the LCD module. If we need to send a command, “LCD_CMD” is used. In this subroutine the RS pin of the LCD is cleared in order to notify the LCD that the byte at its data pin is a command. And subroutine  labeled “LCD_DISP” is used for sending data. Here the RS pin is set which will notify the LCD that the byte arrived is a data for displaying. The necessary commands for the LCD initialization are defined at the end part of the program. Along with that the text to be displayed is also defined there with a label “TEXT1”. “LINE1” AND “LINE2” labels contains the commands for selecting the 1st and 2nd rows of the LCD respectively.

Comments
  • Alex
    March 20, 2017

    El retardo es demasiado corto

  • Dinesh Devireddy
    November 2, 2016

    Good Explanation

  • mufaddal
    April 27, 2016

    i have made a pass door lock but when i write the correct pass 12345 it shows wrong pass 🙁 help me reply soon

  • rahulraje
    March 7, 2016

    outstanding…work…

  • ajay
    April 30, 2015

    pls share the alp for lcd interfacing to 8051

  • ijaz
    April 22, 2015

    hi……..
    anybody can send me programing for interfacing light sensor part number TSL45313cl with micro-controller 8051 to give output at 16x2LCD
    thanks in advance………….

  • jiya
    April 11, 2015

    explain how to display all English alphabets in lcd interfaced with AT89S51

  • Fajar
    November 4, 2014

    There is nothing appearing on lcd.Please help!

    • Simranjit Singh
      April 19, 2016

      you need to initialize the lcd first ..

  • Mihir
    October 7, 2014

    Thankyou for taking the efforts!
    It works!

  • keith formosa
    January 14, 2014

    hi nothing is appearing on my lcd, circuit is ok and program is copied from yours.

  • swapnil
    January 13, 2014

    can anybudy send me program for resistance colour code calculator using microcontroller please send asm program

  • Benjamin
    November 17, 2013

    Could you explain me how DELY subroutine produces the delay?

    DELY:
    MOV P1,#0FFh
    MOV A,P1
    JB ACC.7,DELY <——
    RET;
    I mean, when the condition will be met if the program write a full-ones word at P1 every time?

    Sorry for the question.

  • jojo
    August 19, 2013

    @ Vivek,

    It means, if bit 7 of accumulator is SET (that is 1), then jump to the delay routing labelled DELY. I hope you understood 🙂 Any more doubts ?

  • vivek dixit
    August 18, 2013

    what is this “JB ACC.7,DELY”? plz reply soon

    • Gowtham pavanaskar
      May 24, 2014

      If the 7th bit of the accumulator is 1,then it jumps to DELY.Else it executes the next instruction

  • kp
    June 27, 2013

    esta muy completa a informacion!! muchas gracias

  • MAHESH
    March 2, 2013

    hi.
    can anybody send me circuit and programming of sms based home appliance control system?

  • Payal Patel
    November 4, 2012

    Nice explanation…

  • September 27, 2012

    #include
    #include”delay1sec.h”
    #define lcd_dat P1
    sbit rs=P3^0;
    sbit rw=P3^1;
    sbit en=P3^2;

    void write_lcd(char);
    void cmd_lcd(char);
    void disp_lcd(char);
    void init_lcd();
    void str_lcd(char *s);
    void int_lcd(unsigned int);
    void float_lcd(float);

    void write_lcd(char dat)
    {
    lcd_dat=dat;
    rw=0;
    en=1; //for latching one byte info
    en=0; //clear for latching next info
    delay_ms(2);
    }

    void cmd_lcd(char cmd)
    {
    rs=0; //set cmd register
    write_lcd(cmd);
    }

    void disp_lcd(char c)
    {
    rs=1; //set data register
    write_lcd(c);
    }
    void init_lcd()
    {
    cmd_lcd(0x02); //return cursor home
    cmd_lcd(0x38); //8bit mode of operation
    cmd_lcd(0x0e); //display on cur off
    cmd_lcd(0x01); //clr DDRAM (display data ram)
    cmd_lcd(0x06); //shift cursor right after each character displayed
    cmd_lcd(0x80); //begin disp from line 1 pos 0
    }

    void str_lcd(char *s)
    {
    while(*s)
    disp_lcd(*s++);
    }
    /*
    main()
    {
    init_lcd();
    str_lcd(“******”);
    cmd_lcd(0xc0);
    str_lcd(“*****”);
    while(1);
    }

    */

    main()
    {
    unsigned char i;
    init_lcd();

    for(i=0;i<16;i++)

    {
    cmd_lcd(0x80+i);
    str_lcd("WELCOME");
    delay_ms(500);
    cmd_lcd(0x01);
    cmd_lcd(0x80);

    }

    }

    • vinay
      April 29, 2013

      i want lcd program in asm

    • riddhi
      October 6, 2013

      Anybody can send me the programing for lcd interfacing with microcontroller and xbee s2

    • keith formosa
      January 14, 2014

      Hi I constructed the circuit exactly as it is on my simulator and just copied the program and nothing is appearing on the LCD

  • vivek
    September 26, 2012

    Sir,
    please try to think this circuit by IC ULN2003 at the place of transistors.

  • vinod
    August 9, 2012

    nice work,but please write the programe in embedded c

  • mg
    June 28, 2012

    nice post

  • June 3, 2012

    nice work dude 🙂

  • rowan walters
    June 3, 2012

    absolutely loved this

    • jojo
      June 3, 2012

      Thank you Rowan. Please try it. Comment if you come across any doubts.

      • Laxman
        November 23, 2012

        Real wonderful work………..

      • p
        September 10, 2014

        Pls provide alp programs for LCD interfacing

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