Tuesday, September 25, 2012

Atmel AVR ATMega16 Interfacing WIth 16x2 char LCD

    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 16x2 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 16x2 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 NUMBERSYMBOLFUNCTION
1VssGND
2Vdd  + 3V or + 5V
3Vo Contrast Adjustment
4 RSH/L Register Select Signal
5R/WH/L Read/Write Signal
6E   H → L Enable Signal
7 DB0H/L Data Bus Line
8 DB1H/L Data Bus Line
9 DB2H/L Data Bus Line
10 DB3H/L Data Bus Line
11 DB4H/L Data Bus Line
12 DB5H/L Data Bus Line
13 DB6H/L Data Bus Line
14 DB7H/L Data Bus Line
15A/Vee+ 3.5V for LED/Negative Voltage Output
16KK 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



Function Set
Set the size of interface with the data bus (DL), number of lines in the LCD (N) and character type (F).

RS
R / W
DB7
DB6
DB5
DB4
DB3
DB2
DB1
DB0
0
0
0
0
1
DL
N
F
X
X




Set the CG RAM Address
The LCD module defined in addition to all the ASCII character set allows the user to define 4 or 8 characters. The composition of these characters is saved to a CG RAM memory called up to 64 bytes. Each user defined character consists of 16 or 8 bytes that are stored in successive positions of the CG RAM.

Using this instruction sets the CG RAM memory address from which the bytes will be stored that define a character. Running this command all the data that is subsequently read or write this memory made from CG RAM.

RS
R / W
DB7
DB6
DB5
DB4
DB3
DB2
DB1
DB0
0
0
0
1
CG RAM Address




Set the DD RAM Address
The characters or data to be displayed is stored in a memory called RAM DD then move on to the screen.

Using this instruction sets the address of DD RAM memory from which data will be stored to be displayed. Running this command all data being written to or read then they will from the DD RAM memory.

8Fh addresses 80h to 16 characters correspond to the first row and addresses C0h to CFH to 16 characters of the second row, for this model LCD.

RS
R / W
DB7
DB6
DB5
DB4
DB3
DB2
DB1
DB0
0
0
1
DD RAM Address




Read Busy Flag and Address
E l LCD module takes some time to execute instructions, at which time you should not send another instruction. This flag has a BUSY (busy) indicating that an instruction is being executed.

This reading instruction reports the status of the flag as well as providing the address counter value of the CG RAM or DD RAM according to the latest that has been used.
RS
R / W
DB7
DB6
DB5
DB4
DB3
DB2
DB1
DB0
0
1
BF
Address DD RAM or CG RAM



Write data to CG or DD RAM

Command to write to DD RAM memory the data to be presented on the screen in ASCII code.

Also written to CG RAM memory bytes to generate user-defined characters.

Previously DD RAM memory addresses or CG RAM memory where you want to write data.

RS
R / W
DB7
DB6
DB5
DB4
DB3
DB2
DB1
DB0
1
0
Byte ASCII character or graphic 




Read Data from CG RAM or DD RAM

Command to read data stored in DD RAM, ASCII code.

Likewise, read CG RAM memory bytes of user-defined characters.

Previously, memory addresses or memory DD RAM CG RAM you want to read the data.

RS
R / W
DB7
DB6
DB5
DB4
DB3
DB2
DB1
DB0
1
1
Byte ASCII character or graphic




Connection Diagram



DOWNLOAD SOURCE CODE and Firmware
the Software is written with avr studio 5.0 and with AVR gcc GNU compiler 
click here to download: ---- 4 bit mode







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