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Sunday, June 26, 2011

Programming (Interface) LCDs with AVR Microcontroller ATMEGA8535

Basic Theory of LCD

LCD (Liquid Crystal Display) is a viewer module which is widely used because it looks interesting. LCDs are the most widely used today is to refurbish M1632 LCD because the price is quite cheap. M1632 LCD display is an LCD module with 2x16 (2 rows x 16 columns) with low power consumption. The module is equipped with a microcontroller specifically designed to control the LCD.
Artificial Hitachi HD44780 microcontroller that serves as the LCD controller has CGROM (Character Generator Read Only Memory), CGRAM (Character Generator Random Access Memory), and DDRAM (Display Data Random Access Memory).

LCDs are common, there is a length of up to 40 characters (2x40 and 4x40), which we use to manage storage DDRAM the character.

Composition of Addresses In LCDs

Start address and end address character 00H 39H. Thus, the initial address on the second line starts from 40H. If you want to put a character on the second row first column, then it should be set at address 40H. Thus, although the LCD is used 2x16 or 2x24, or 2x40, then writing the same program.
CGRAM is a memory to describe the pattern of a character, where the shapes of the characters can be changed in accordance with the wishes. However, the memory will be lost when power supply is off so that the pattern of the character will be lost. The following table pin for LCD M1632. The difference with the standard LCD is at the foot of a VCC, and Gnd feet 2. This is in contrast to a standard LCD.
M1632 LCD foot structureKeep in mind, such as the HD44780 LCD driver has access to two registers are set using the RS pin. At the time of hospitals logic 0, the register is accessed is a command, while at the RS logic 1, the register that is accessed is data register.

In order to activate the LCD, the initialization process must be done by setting the RS bit and to clear the bits of E with minimal delay 15 ms. Then sends the data 30h and dela
yed again for 5 ms. This process should be done three times, then send the initials 20H and interface data length with a width of 4 bits only (28H). After that the display is turned off (08H) and in-clear-it (01h). Subsequently setting displays and cursors, and blinking is ON or OFF.
The following figure shows the relationship between an LCD with a microcontroller port, there is usually a potentiometer to adjust contrast / brightness of the LCD. On the input LED, mounted transistor as a current amplifier, so it can display the LED light is bright enough.
Here is a sample program displays a message with a sliding right-left with a certain delay. Create a new project with the name of the LCD, and enter the following code.


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