Interfacing LCD module with 8051 microcontroller

INTERFACING 16X2 LCD WITH AT89C51 CONTROLLER *Praneeth (Dept. of research and development in embedded systems) In this paper, we will have a brief discussion on how to interface 16x2 LCD module with AT89c51, which is an 8051 family microcontroller. We use LCD display for the displaying messages in a more interactive way to operate the system or displaying data or errors. If you understanding the working of 16x2 LCD, then you can easily interface LCD module with AT89c51 or with any microcontroller.

The main aim of this paper is to provide more relevant information related to the subject with exact information which you can understand easily. And I will provide the code in c language which is working fine without any errors.

Brief note on 16X2 LCD: 16x2 liquid crystal display which will display 32 characters at a time in two rows i.e., 16 characters in first row and another 16 characters in second row.

Each character in display is of size 5x7 pixel matrix. This matric differs for different 16x2 LCD modules. If consider JHD162A, this matrix works on 5x8 pixel matrix arrangement.

There are 16 pins in LCD module, every pin has a specific operational specifications. The pin configuration of LCD is discussed below.

S.NO.

NAME

FUNCTION

1

VSS

Ground pin

2 3

VCC VEE

Power supply pin of 5V Used for adjusting contrast commonly attached to the potentiometer

4 RS

RS is register select pin used to write display data to the LCD. This pin should be high when writing the data to LCD, During the initialization and for other commands this pin should be low.

5

R/W

Reading and writing data to the LCD for reading the data R/W pin should be high(R/W=1), to write data to the LCD R/W pin should be low(R/W=0).

6

E

Enable pin is for starting or enabling the module. A high to low pulse of about 450 ns pulse is given to this pin.

DB0-DB7

DB0-DB7 pins are data pins for giving data like characters, numbers, strings or command data which is meant to be displayed.

LED+ LED-

Back light of the LCD which should be connected to VCC Back light of the LCD which should be connected to ground

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8 9

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Form the above information you can get a brief idea how to display a character. For displaying a character you should enable the enable pin (E) by giving a pulse of 450 ns. After enabling the enable pin ( E ) you should select the register select pin ( RS ) in write mode ( RS=1 ). After selecting register select pin in write mode you have to configure R/W to write mode that is R/W should be low( R/W=0 ).

Follow these steps to display a character data: EN=1; Enable pin should be high.

RS=1; register select pin should be high.

R/W=0; R/W pin should low.

Follow these steps to send commands to LCD: EN=1; Enable pin should be high.

RS=0; register select pin should be low.

R/W=0; R/W pin should low.

Commands: There are some preset commands which will do a specific task in the LCD. These commands are very important for displaying data in LCD. The lists of commands are given below.

COMMAND

FUNCTION

0X0F

For switching ON LCD and blinking cursor.

0X01

Clearing screen

0X02

Return home

0X04

Decrement cursor

0X06

Increment cursor

0X0E

Display ON and also cursor ON

0X80

Force cursor to beginning of the first line

0xC0

Force cursor to beginning of second line

0X38

Use two lines and 5x7 matrix

0X83

Cursor line 1, position 3

0X3C

Activate second line

0XC3

Jump to second line position 3

0XC1

Jump to second line position 1

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INTERFACING 16X2 LCD WITH 8051 MICROCONTROLLER: COMPONENTS REQUIRED: 1.

2.

3.

4.

AT89C51 Microcontroller.

16x2 LCD Display.

5V Power supply.

Connecting wires.

SCHEMATIC:

Programming LCD to 8051:   

STEP 1: Initialization of LCD. STEP 2: Sending commands to LCD. STEP 3: Writing the data to LCD.

INITIALIZATION OF LCD: To initialize LCD to the 8051 the following instruction and commands are to be embed in to the functions.    

0x38 is used 8-bit data initialization.

0x0c for making LCD display on and cursor off.

0x01 for clearing the display of the LCD. 0x80 for positioning the cursor at first line.

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SENDING COMMANDS TO LCD:    

E=1; enable pin should be high.

RS=0; Register select should be low for sending commands.

Placing the data on data register.

R/W=0; Read/Write pin should low for writing the data.

SENDING THE DATA TO LCD:    

E=1; Enable pin should be high.

RS=1; Register select pin should be high.

Placing data on data register.

R/W=0; Read/Write pin should low for writing the data.

CODE: #include <REGX51.H> sbit rs=P1^0;

//register select pin is connected to pin 0 of port 1

sbit rw=P1^1; // Read/Write pin is connected to pin 1 of port 1 sbit en=P1^2; // enable pin is connected to pin 2 of port 1 void delay(unsigned int x)

// to provide delay

{ int a; while(x--) { for(a=0;a<1275;a++); } } // termination of delay funtion void lcd_cmd(unsigned char y) // Funtion for LCD commands. { P2=y; rs=0; rw=0; en=1; delay(10); en=0; } // termination of lcd_cmd funtion

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void lcd_data(unsigned char z) // Funtion for LCD data { P2=z; rs=1; rw=0; en=1; delay(10); en=0; } // termination of lcd_data function void lcd_init()

// commans to initialize the LCD module.

{ lcd_cmd(0x38); lcd_cmd(0x80); lcd_cmd(0x0e); lcd_cmd(0x06); } // termination of lcd_init function void lcd_string(unsigned char *p) // Funtion to display strings on LCD. { while(*p) { lcd_data(*p++); } } // termination of lcd_string funtion void main() { lcd_init(); lcd_string("Interfacing LCD"); lcd_cmd(0xc3); lcd_string("With 8051"); }// termination of main program

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For more information and documents contact:

Praneeth.vandanapu@yahoo.com

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