Interfacing of LCD and introduction.

Introduction of lcd and interfacing

Lcd(liquid crystal display):-

Series for embedded is

 16x1          means 1 row 16 columns

16x2           means 2 row 16 columns

16x4           means 4 row 16 columns

20x1           means 1 row 20 columns

20x2           means 2 row 20 columns

40x1           means 1 row 40 columns

40x2           means 2 row 40 columns

 

·       Lcd is a individually an embedded product. It is preceed 8-bit data at a time.

·       It has 8 select data line by this 8-bit data is transferred at a time.

·       In this 16 pin in which 15 and 16 pin is provide lcd backlight. Pin 1 and 2 provides power to lcd and 3^rd pin vee stands for variable resistance this is used for control the contrast of lcd.

·       Lcd have 2 registers

1.     Command register

2.    Data register

 Both registers are 8-bit.

Pin 4, 5 and 6 are RS, RW and EN

RS- Register select

Send 0 for command

Send 1 for data.

RW- READ WRITE

Send 1 for read

Send 0 for write

EN- ENABLE

send 1 for command

send 1 for data.

after giving delay enable will be zero.

 

LCD has some predefined commands:-

·       0x01 for clear display screen.

·       0x04 for decrement cursor.

·       0x06 for increment cursor.

·       0x80 force cursor to the beginning of first line.

·       0xc0 force cursor to the beginning of second line.

·       0x90 force cursor to the beginning of third line.

·       0xdo force cursor to the beginning of fourth line.

·       0x0e for display on cursor blinking.

·       0x0f for display on cursor not blinking.

·       0x02 for select 4 bit mode.

·       0x28 selects 5x7 matrix for 4 bit mode.

·       0x38 selects 5x7 matrix for 8 bit mode.

·       0x18 fir moving entire display left.

·       0x1c for moving entire display right.

 

We are using commonly these bold commands.

 

program to display A on LCD screen.

 

#include<avr/io.h>
#include<util/delay.h>
void cmd()
{
 PORTA=0B00000100;
 _delay_ms(300);
 PORTA=0b00000000;

}
void display()
{
 PORTA=0b00000101;
 _delay_ms(300);
 PORTA=0b00000001;

}
void main()
{
 DDRA=0xff;
 DDRB=0xff;
 PORTB=0X38;
 cmd();
 PORTB=0X0e;
 cmd();
 PORTB=0X01;
 cmd();
 PORTB=0X80;
 cmd();
 PORTB=0X06;
 cmd();
 PORTB='A';
 display();
}