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Atmel AVR ATMega16 Interfacing WIth 16×2 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 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 charAtmel AVR ATMega16 Interfacing WIth 16x2 char LCDOperation 

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
3VoContrast 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.

RSR / WDB7DB6DB5DB4DB3DB2DB1DB0
0000000001

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.

RSR / WDB7DB6DB5DB4DB3DB2DB1DB0
000000001X

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.

RSR / WDB7DB6DB5DB4DB3DB2DB1DB0
00000001I / DS

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).

RSR / WDB7DB6DB5DB4DB3DB2DB1DB0
0000001DCB

Cursor or Display Shift

Move the cursor to move the LCD without changing the memory contents of the display data DD RAM.

RSR / WDB7DB6DB5DB4DB3DB2DB1DB0
000001S / CR / LXX

Function Set

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

RSR / WDB7DB6DB5DB4DB3DB2DB1DB0
00001DLNFXX

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.

RSR / WDB7DB6DB5DB4DB3DB2DB1DB0
0001CG 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.

RSR / WDB7DB6DB5DB4DB3DB2DB1DB0
001DD 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.

RSR / WDB7DB6DB5DB4DB3DB2DB1DB0
01BFAddress 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.

RSR / WDB7DB6DB5DB4DB3DB2DB1DB0
10Byte 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.

RSR / WDB7DB6DB5DB4DB3DB2DB1DB0
11Byte ASCII character or graphic

 


Connection Diagram
Schematic Atmel AVR ATMega16 Interfacing WIth 16x2 char LCDFor more detail: Atmel AVR ATMega16 Interfacing WIth 16×2 char LCD 

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