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8051

Interfacing LCD with 8051

By ⋅ January 9, 2010 ⋅ Post a comment
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LCD is tongue of embedded system. With help of LCD, embedded system can communicate their status to external world. Two types of LCD modules are available; text and graphical. In this tutorial we will cover text based modules. LCD module JHD162A is used as example here, however same instructions would also apply for controller HD44780 which is one of most commonly used module. This tutorial is divided into following sections:
  • Interfacing hardware
  • Controlling with software
  • Source code

1.Interfacing Hardware:

Let’s start with connecting the LCD hardware with microcontroller (P89v51). The following table lists all pins of LCD module (JHD162A) along with their description.

Pin No Name Description
1 Vss Ground
2 Vdd +5V
3 Vee Contrast Adjustment -2V to -5V
4 RS Register Select
5 RW 1 -Read , 0- Write
6 E Enable Strobe
7 D0 Data Line
8 D1 Data Line
9 D2 Data Line
10 D3 Data Line
11 D4 Data Line
12 D5 Data Line
13 D6 Data Line
14 D7 Data Line
15 LED+ Backlit LED +V  Vdd (Optional signal)
16 LED- Backlit LED –V  Vss (Optional signal)

LCD Pin Description (JHD162A)

1.1 Connecting Supplies:

Vss (Pin 1) is connected to board ground.

Vdd (Pin 2) is connected to + 5V supply.

Vee (Pin 3) is connected using a variable resistance for adjusting contrast.

LED- (Pin 16) is connected to GND

LED+ (Pin 15) is connected to Vdd

1.2 Connecting control and data signals:

Control signal RS, RW and E are connected to IO Port pins.  For data lines we can have two configurations 8 bit mode and 4 bit mode. In 8 bit mode all lines D0-D7 are connected to IO port pins of microcontroller. In 4 bit mode only D4-D7 are connected to IO port pins. The example code available in source section(at bottom of this article) uses the 4 bit mode as default, however 8 bit mode is also supported.

Following images show both 8 bit and 4 bit configuration for interfacing LCD with P89v51 microcontroller.

Interfacing 8051 with LCD using 4Bit Interface Interfacing 8051 with LCD using 8 Bit Interface

2. Writing software:

The LCD module is an intelligent component. We communicate to LCD module by sending commands from microcontroller. To write data to LCD module separate sequence is followed for 4 bit and 8 bit mode.

Writing command for 8 Bit mode:

  • Write 8 bit data on D0-D7
  • Generate strobe by taking EN from high to low

Writing command for 4 Bit mode:

  • Write 4 bit data (upper nibble) on D4-D7
  • Generate strobe by taking EN from high to low
  • Write 4 bit data (lower nibble) on D4-D7
  • Generate strobe by taking EN from high to low

The following table lists commands supported by LCD module:

LCD Commands: 

Instruction RS RW D7 D6 D5 D4 D3 D2 D1 D0 Description
NOP 0 0 0 0 0 0 0 0 0 0 No Operation
Clear Display 0 0 0 0 0 0 0 0 0 1 Clear Display and Address counter = 0
Cursor Home 0 0 0 0 0 0 0 0 1 x Address counter = 0
Entry mode set 0 0 0 0 0 0 0 1 I/D S Set cursor direction(I/D) and auto display shift (S)
Display Control 0 0 0 0 0 0 1 D C B Turn display (D) and cursor (C) ON/OFF. Set cursor blinking(B)
Cursor/ Display shift 0 0 0 0 0 1 S R/L x x Shift display/cursor (S), specify direction (R/L)
Function set 0 0 0 0 1 DL N F x x Set Interface data width (DL), number of display lines (N), character font (F)
Set CGRAM Address 0 0 0 1             Set CGRAM address (D0-D5), CGRAM data is sent after this command
Set DDRAM Address 0 0 1               Set DDRAM address (D0-D6), DDRAM data is sent after this command
Busy Flag and Address 0 1 BF               Read busy flag (BF) and address counter(D0-D6)
Write Data 1 0                 Write data (D0-D7) into DDRAM/CGRAM
Read Data 1 1                 Read data (D0-D7) from DDRAM/CGRAM

Legends used in table:-

I/D:     1- Increment, 0- Decrement

S:         1- Auto Display shift, 0 – No display shift

D:        1- Display ON, 0 – Display OFF

C:        1- Cursor ON, 0- Cursor OFF

B:        1- Cursor blinking ON, 0 – Cursor blinking OFF

S:         1- Display Shift, 0 –Cursor move

R/L:    1- Shift right, 0- Shift left

DL:     1- 8 bit interface, 0- 4 bit interface

N:        1- 2 lines, 0- 1 line

F:        1- 5X10 dots font, 0- 5X7 dots font

BF:      Busy Flag

LCD Controller (JHD162A, HD44780) Commands

All LCD functions are actually a combination of above mentioned commands. We will use some example functions to understand how to use commands to build higher level functionality.

2.1 LCD Initialization: To initialize LCD a typical sequence of commands is followed. We also configure all LCD related parameters such as data interface width, display characteristics etc. in this function.

Initialization sequence:

  1. Wait for power supplies to stabilize. Wait for approx 2-3 ms
  2. Write 0×30 to LCD
  3. wait for 50ms
  4. Write 0×30 to LCD
  5. wait for 10ms
  6. Write 0×30 to LCD
  7. wait for 1ms
  8. Set data interface width (Write 0×30 for 8 bit or 0×20 for 4 bit) to LCD
  9. wait for 50ms
  10. Set display lines and font dots
  11. Set Display OFF, Cursor and blinking off (Write 0x0B)
  12. Set Display ON, Cursor and blinking off (Write 0x0F)
  13. Set Cursor move direction (I/D) and display shift (S)
  14. Clear display (Write 0×01)
  15. Wait 50ms

2.2 Moving Cursor to Home: To move cursor to home position without clearing the screen we will use following commands

  1. Write 0×03
  2. Wait for approx 2ms

Similarly many functions can be implemented using LCD commands. LCD Library available from source code section (bottom of this article) provides following functions using C.

Function Description
Utility functions
InitializeLCD Initialize LCD hardware
ClearScreen Clears LCD screen
MoveCursorToHome Moves cursor to home position
Cursor functions
SetCursorPos Sets cursor position
SetCursorState Sets cursor state (Blink,ON/OFF)
SetCursorBlink Sets cursor in blinking state
SetCursorNoBlink Disables cursor blinking
SetCursorOn Cursor enabled
SetCursorOff Cursor disabled
Writing functions
WriteCharAtPos Writes character at defined position
WriteStringAtPos Writes string at defined position
Custom character/font functions
CreateCustomCharacter Creates user defined character

 LCD Library functions

2.3 Detailed function description:

 

InitializeLCD
Prototype void InitializeLCD();
Input parameters None
Output None
Description Initializes LCD hardware. Configures data interface(4bit or 8 bit). Clears the display and places cursor at home with blinking mode

 

ClearScreen
Prototype void ClearScreen();
Input parameters None
Output None
Description Clear screen and moves cursor to home. This function takes approx 1.6 ms to complete.

 

MoveCursorToHome
Prototype void MoveCursorToHome();
Input parameters None
Output None
Description Moves the cursor to home position

 

SetCursorPos
Prototype void SetCursorPos(unsigned char row, unsigned char col);
Input parameters row:  row number (first row = 0 and so on)col: Column number (first column = 0 and so on)
Output None
Description Sets the cursor position to specified row and column position

 

SetCursorState
Prototype void SetCursorState(unsigned char isBlinking, unsigned char isOn);
Input parameters isBlinking:  0 – no blinking, 1- blinkingisOn: 0 – cursor OFF, 1- cursor ON
Output None
Description Changes cursor state (Blinking and On/Off)

 

SetCursorBlink
Prototype void SetCursorBlink();
Input parameters None
Output None
Description Sets cursor blinking

 

SetCursorNoBlink
Prototype void SetCursorNoBlink();
Input parameters None
Output None
Description Disables cursor blinking

 

SetCursorOn
Prototype void SetCursorOn();
Input parameters None
Output None
Description Enables cursor

 

SetCursorOff
Prototype void SetCursorOff();
Input parameters None
Output None
Description Disables cursor

 

WriteCharAtPos
Prototype void WriteCharAtPos(unsigned char row, unsigned char col, char ch);
Input parameters row: row position, First row =0 and so oncol: column position, First column = 0 and so onch: character to be written
Output None
Description Writes a single character ch at specified row and column position

 

WriteStringAtPos
Prototype void WriteStringAtPos(unsigned char row, unsigned char col, char *str);
Input parameters row: row position, First row =0 and so oncol: column position, First column = 0 and so onstr: string to be written
Output None
Description Writes character string at specified row and column position

 

CreateCustomCharacter
Prototype void CreateCustomChar(unsigned char charIndex, unsigned char *charBitmap);
Input parameters charIndex: character index in CGRAM (0 to 7 are reserved for user defined characters)charBitmap: Bitmap corresponding to the custom character. Character bitmap consists of 5X8 pixels. Bitmap is stored in 8 bytes. 5 LSBs of each byte store the pixel information.Pixel layout of custom character:charBitmap[0] *     *     *       1    2    3     4      5

charBitmap[1] *     *       *     6    7    8     9     10

charBitmap[2] *     *       *    11   12   13   14   15

charBitmap[3] *     *       *    16   17   18   19   20

charBitmap[4] *     *       *    21   22   23   24   25

charBitmap[5] *     *       *    26   27   28   29   30

charBitmap[6] *     *       *    31   32   33   34   35

charBitmap[7] *     *       *    36   37   38   39   40

Source Code:

Microcontroller: P89V51RD2

LCD Controller: JHD162A

Compiler: SDCC

Source: LCD Source code

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  3. Using SDCC (Open source compiler)for 8051 Development

Discussion

10 Responses to “Interfacing LCD with 8051”

  1. great tutorial

    Posted by z_is_a | February 10, 2010, 1:37 pm

  2. its good

    Posted by christopher | November 12, 2010, 6:40 am

  3. the code is giving lot of errors with 89v51reg.h

    Posted by Ankit Garg | July 18, 2011, 1:19 pm

  4. i have a question here….do i need 10k puller when interface with p0 with lcd..because i see sum connection there have puller…i dnt understand about it.

    Posted by sivan | August 9, 2011, 8:27 pm

  5. SuperB Thanks

    Posted by Adeel | October 27, 2011, 1:53 am

  6. i have an issue symbols are comming while i try to display the fonts..could you help me..

    Posted by Elavarasu | February 28, 2012, 7:41 am

  7. h0w can I burn a written prgrm into 8051

    Posted by Daniel | June 11, 2012, 10:40 pm

  8. Hi Daniel,
    Refer to tools article which describes all tools including flashing/burning tools.
    http://embeddedtutorial.com/2009/12/setting-up-8051-development-environment-with-free-tools/
    Hope this helps

    Posted by Parveen Kumar | June 16, 2012, 10:29 am

  9. Hi Elavarasu,

    If you are seeing symbols instead of proper fonts that means improper initialization. Try increasing delays in init.

    Posted by Parveen Kumar | June 16, 2012, 10:30 am

  10. Hi Ankit
    The code posted in http://embeddedtutorial.com/category/source-code/ section is compiled with SDCC compiler. It might not work as it is with other compilers. Also don’t forget to tell SDCC that you are compiling for 8051, as it supports multiple CPUs

    Posted by Parveen Kumar | June 16, 2012, 10:32 am

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