AVR 4 Bit LCD Interfacing Tutorial

The mikroC PRO for AVR provides a library for communication with Lcds (with HD44780 compliant controllers) through the 4-bit interface. An example of Lcd connections is given on the schematic at the bottom of this page.

For LCD Basics: Character LCD Basics 

Lcd Library

External dependencies of Lcd Library

The following variables must be defined in all projects using Lcd Library :	Description :	Example :
extern sfr sbit LCD_RS:	Register Select line.	sbit LCD_RS at PORTD2_bit;
extern sfr sbit LCD_EN:	Enable line.	sbit LCD_EN at PORTD3_bit;
extern sfr sbit LCD_D7;	Data 7 line.	sbit LCD_D7 at PORTD4_bit;
extern sfr sbit LCD_D6;	Data 6 line.	sbit LCD_D6 at PORTD5_bit;
extern sfr sbit LCD_D5;	Data 5 line.	sbit LCD_D5 at PORTD6_bit;
extern sfr sbit LCD_D4;	Data 4 line.	sbit LCD_D4 at PORTD7_bit;
extern sfr sbit LCD_RS_Direction;	Register Select direction pin.	sbit LCD_RS_Direction at DDD2_bit;
extern sfr sbit LCD_EN_Direction;	Enable direction pin.	sbit LCD_EN_Direction at DDD3_bit;
extern sfr sbit LCD_D7_Direction;	Data 7 direction pin.	sbit LCD_D7_Direction at DDD4_bit;
extern sfr sbit LCD_D6_Direction;	Data 6 direction pin.	sbit LCD_D6_Direction at DDD5_bit;
extern sfr sbit LCD_D5_Direction;	Data 5 direction pin.	sbit LCD_D5_Direction at DDD6_bit;
extern sfr sbit LCD_D4_Direction;	Data 4 direction pin.	sbit LCD_D4_Direction at DDD7_bit;

Library Routines

• Lcd_Init
• Lcd_Out
• Lcd_Out_Cp
• Lcd_Chr
• Lcd_Chr_Cp
• Lcd_Cmd

Lcd_Init

Prototype	void Lcd_Init();
Returns	Nothing.
Description	Initializes Lcd module.
Requires	Global variables: LCD_D7: Data bit 7 LCD_D6: Data bit 6 LCD_D5: Data bit 5 LCD_D4: Data bit 4 LCD_RS: Register Select (data/instruction) signal pin LCD_EN: Enable signal pin LCD_D7_Direction: Direction of the Data 7 pin LCD_D6_Direction: Direction of the Data 6 pin LCD_D5_Direction: Direction of the Data 5 pin LCD_D4_Direction: Direction of the Data 4 pin LCD_RS_Direction: Direction of the Register Select pin LCD_EN_Direction: Direction of the Enable signal pin must be defined before using this function.
Example	// Lcd pinout settings sbit LCD_RS at PORTD2_bit; sbit LCD_EN at PORTD3_bit; sbit LCD_D7 at PORTD4_bit; sbit LCD_D6 at PORTD5_bit; sbit LCD_D5 at PORTD6_bit; sbit LCD_D4 at PORTD7_bit; // Pin direction sbit LCD_RS_Direction at DDD2_bit; sbit LCD_EN_Direction at DDD3_bit; sbit LCD_D7_Direction at DDD4_bit; sbit LCD_D6_Direction at DDD5_bit; sbit LCD_D5_Direction at DDD6_bit; sbit LCD_D4_Direction at DDD7_bit; ... Lcd_Init();

Lcd_Out

Prototype	void Lcd_Out(char row, char column, char *text);
Returns	Nothing.
Description	Prints text on Lcd starting from specified position. Both string variables and literals can be passed as a text. Parameters : row: starting position row number column: starting position column number text: text to be written
Requires	The Lcd module needs to be initialized. See Lcd_Init routine.
Example	// Write text "Hello!" on Lcd starting from row 1, column 3: Lcd_Out(1, 3, "Hello!");

Lcd_Out_Cp

Prototype	void Lcd_Out_Cp(char *text);
Returns	Nothing.
Description	Prints text on Lcd at current cursor position. Both string variables and literals can be passed as a text. Parameters : text: text to be written
Requires	The Lcd module needs to be initialized. See Lcd_Init routine.
Example	// Write text "Here!" at current cursor position: Lcd_Out_Cp("Here!");

Lcd_Chr

Prototype	void Lcd_Chr(char row, char column, char out_char);
Returns	Nothing.
Description	Prints character on Lcd at specified position. Both variables and literals can be passed as a character. Parameters : row: writing position row number column: writing position column number out_char: character to be written
Requires	The Lcd module needs to be initialized. See Lcd_Init routine.
Example	// Write character "i" at row 2, column 3: Lcd_Chr(2, 3, 'i');

Lcd_Chr_Cp

Prototype	void Lcd_Chr_Cp(char out_char);
Returns	Nothing.
Description	Prints character on Lcd at current cursor position. Both variables and literals can be passed as a character. Parameters : out_char: character to be written
Requires	The Lcd module needs to be initialized. See Lcd_Init routine.
Example	// Write character "e" at current cursor position: Lcd_Chr_Cp('e');

Lcd_Cmd

Prototype	void Lcd_Cmd(char out_char);
Returns	Nothing.
Description	Sends command to Lcd. Parameters : out_char: command to be sent   Note : Predefined constants can be passed to the function, see Available Lcd Commands.
Requires	The Lcd module needs to be initialized. See Lcd_Init table.
Example	// Clear Lcd display: Lcd_Cmd(_LCD_CLEAR);

Available Lcd Commands

Lcd Command	Purpose
_LCD_FIRST_ROW	Move cursor to the 1st row
_LCD_SECOND_ROW	Move cursor to the 2nd row
_LCD_THIRD_ROW	Move cursor to the 3rd row
_LCD_FOURTH_ROW	Move cursor to the 4th row
_LCD_CLEAR	Clear display
_LCD_RETURN_HOME	Return cursor to home position, returns a shifted display to its original position. Display data RAM is unaffected.
_LCD_CURSOR_OFF	Turn off cursor
_LCD_UNDERLINE_ON	Underline cursor on
_LCD_BLINK_CURSOR_ON	Blink cursor on
_LCD_MOVE_CURSOR_LEFT	Move cursor left without changing display data RAM
_LCD_MOVE_CURSOR_RIGHT	Move cursor right without changing display data RAM
_LCD_TURN_ON	Turn Lcd display on
_LCD_TURN_OFF	Turn Lcd display off
_LCD_SHIFT_LEFT	Shift display left without changing display data RAM
_LCD_SHIFT_RIGHT	Shift display right without changing display data RAM

Example

The following code demonstrates usage of the Lcd Library routines:

           // LCD module connections

sbit LCD_RS at PORTD2_bit;

sbit LCD_EN at PORTD3_bit;

sbit LCD_D4 at PORTD4_bit;

sbit LCD_D5 at PORTD5_bit;

sbit LCD_D6 at PORTD6_bit;

sbit LCD_D7 at PORTD7_bit;

sbit LCD_RS_Direction at DDD2_bit;

sbit LCD_EN_Direction at DDD3_bit;

sbit LCD_D4_Direction at DDD4_bit;

sbit LCD_D5_Direction at DDD5_bit;

sbit LCD_D6_Direction at DDD6_bit;

sbit LCD_D7_Direction at DDD7_bit;

// End LCD module connections

char txt1[] = "Embedded";

char txt2[] = "Projects";

char txt3[] = "Lcd 4 bit";

char txt4[] = "Tutorial";

char i;                              // Loop variable

void Move_Delay() {                  // Function used for text moving

  Delay_ms(500);                     // You can change the moving speed here

}

void main(){

  Lcd_Init();                        // Initialize LCD

  Lcd_Cmd(_LCD_CLEAR);               // Clear display

  Lcd_Cmd(_LCD_CURSOR_OFF);          // Cursor off

  Lcd_Out(1,6,txt3);                 // Write text in first row

  Lcd_Out(2,6,txt4);                 // Write text in second row

  Delay_ms(2000);

  Lcd_Cmd(_LCD_CLEAR);               // Clear display

  Lcd_Out(1,1,txt1);                 // Write text in first row

  Lcd_Out(2,4,txt2);                 // Write text in second row

  Delay_ms(2000);

  // Moving text

  for(i=0; i<4; i++) {               // Move text to the right 4 times

    Lcd_Cmd(_LCD_SHIFT_RIGHT);

    Move_Delay();

  }

  while(1) {                         // Endless loop

    for(i=0; i<7; i++) {             // Move text to the left 7 times

      Lcd_Cmd(_LCD_SHIFT_LEFT);

      Move_Delay();

    }

    for(i=0; i<7; i++) {             // Move text to the right 7 times

      Lcd_Cmd(_LCD_SHIFT_RIGHT);

      Move_Delay();

    }

  }

}

Circuit diagram