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Atmel AVR ATMega16 Interfacing WIth 16×2 char LCD

Atmel AVR ATMega16 Interfacing WIth 16×2 char LCD

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An alphanumeric low cost LCD Display is very essential for may small and big projects to Display various type of information. Hitachi HD44780  Chipset based 16×2 char LCD is Really very cheap and easily available in the local market.

Project Description:-

  In this project we are going to learn various things about this chip set and displaying text on this LCD. The HD44780 16×2 char LCD screen Use 4 bit parallel interface with backlight.

This Primary Objective in this project are:-

1.  Displaying  “Hello Word!! LCD ” message on the scree.
2.   Interfacing The LCD to the Microcontroller Using  4 Bit Mode.
3.  Generating and Displaying Custom Char on the LCD Screen. click here for custom char 

Operation 

as i have mentioned  before this type of lcd are connected to microcontroller using parallel 8bit or 4bit lines.
using 8 bit method is quite simple but take 8 lines (for data or command)+ 3 control signal total 11 line , i guess few small microcontrollers don’t even have that much of I/O lines ,so in 4 bit mode total 7 lines (sometimes 6 ) are required .  in this tutorial i will show you with both of the methods .

Pin description

PIN NUMBER SYMBOL FUNCTION
1 Vss GND
2 Vdd  + 3V or + 5V
3 Vo Contrast Adjustment
4  RS H/L Register Select Signal
5 R/W H/L Read/Write Signal
6 E  H → L Enable Signal
7  DB0 H/L Data Bus Line
8  DB1 H/L Data Bus Line
9  DB2 H/L Data Bus Line
10  DB3 H/L Data Bus Line
11  DB4 H/L Data Bus Line
12  DB5 H/L Data Bus Line
13  DB6 H/L Data Bus Line
14  DB7 H/L Data Bus Line
15 A/Vee + 3.5V for LED/Negative Voltage Output
16 K K Power Supply for B/L (OV)

in 8 bit mode all the Data line DB0 to DB7 are being used for transferring the the data to lcd but in 4-bit mode only 4 line form DB4 to DB7 are being used to transfer the  8 bit wide data in two peaces one after another .

we can’t display any data on the lcd until all the required internal command register of the lcd are not being properly initialized.
to know every thing about this lcd controller .. you can go through it’s data sheet
click here to download HD44780 data sheet
so now we will learn how to initialize the lcd.

LCD Commands

Clear Display
clear  and place the cursor in the first position (address 0). The bit I / D to 1 by default.
RS
R / W
DB7
DB6
DB5
DB4
DB3
DB2
DB1
DB0
0
0
0
0
0
0
0
0
0
1
Return the cursor to Home
Place the cursor in the home position (address 0) and make the display starts to move from its original position. The contents of the RAM display data (DD RAM) remains unchanged. The address of the RAM for display data (DD RAM) is set to 0.
RS
R / W
DB7
DB6
DB5
DB4
DB3
DB2
DB1
DB0
0
0
0
0
0
0
0
0
1
X
Entry Mode in Set
Set cursor moving direction and specify that the display moves to the next position of the screen or not. These operations are performed during reading or writing of the DD RAM or CG RAM. To view usually set bit S = 0.
RS
R / W
DB7
DB6
DB5
DB4
DB3
DB2
DB1
DB0
0
0
0
0
0
0
0
1
I / D
S
Display ON / OFF Control
Turn on or off by turning ON / OFF both the LCD (D) as the cursor (C) and whether or not this last flash (B).
RS
R / W
DB7
DB6
DB5
DB4
DB3
DB2
DB1
DB0
0
0
0
0
0
0
1
D
C
B
Cursor or Display Shift
Move the cursor to move the LCD without changing the memory contents of the display data DD RAM.
RS
R / W
DB7
DB6
DB5
DB4
DB3
DB2
DB1
DB0
0
0
0
0
0
1
S / C
R / L
X
X
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