LCD AND LCD INTERFACING

INDEX:-  INTRODUCTION  PIN DISCRIPTION  INITIALIZATION OF LCD  LCD INTERFACING  LCD INTERFACING WITH ATMEGA 32  INTERFACING AVR TO LCDIN 4 BIT MODE  ADVANTAGES AND DISADVANTAGES  APPLICATION

INTRODUCTION LCD:-  LCD stands for liquid crystal display.  LCD consist of rod shape tiny molecules sandwiched between a flat piece of glass and an opeque substrate.  This rod shape molecules in between the plates align into different positions based on electric charge.  When there is no charge,they become transperent.  They are thin and consume less power compare to LEDs and CRTs.

Pin Discription of LCD PIN SYMBOL FUNCTION 1 VSS Ground 2 VCC +5V Power supply 3 VEE Power supply to control contrast 4 RS RS=0 to select command reg. RS=1 to select data reg. 5 R/W R/W =0 for Write. R/W =1 for Read. 6 E Enable 7 DB0 Data bus bit 0 8 DB1 Data bus bit 1 9 DB2 Data bus bit 2 10 DB3 Data bus bit 3 11 DB4 Data bus bit 4 12 DB5 Data bus bit 5 13 DB6 Data bus bit 6 14 DB7 Data bus bit 7

LCD command codes Hex command Function 0x01 Clear display 0x02 return cursor to home. 0x04 Decrement cursor 0x06 Icrement cursor 0x05 Shift display right 0x07 Shift display left 0x08 display off, cursor off 0x0A display off, cursor on 0x0C display on, cursor off

LCD Interfacing  LCD are connected to microcontroller through a LCD interface IC or directly to it's address and databus and few control pins, Few of the today's latest microcontrollers have built-in LCD driver.  Some of the LCDs support serial interface.

-LCD (Liquid Crystal Display) is an electronic display which is commonly used nowadays in applications such as calculators, laptops, tablets, mobile phones etc. - 16×2 character LCD module is a very basic module which is commonly used by electronic hobbyists and is used in many electronic devices and project. - It can display 2 lines of 16 character and each character is displayed using 5×7 or 5×10 pixel matrix. 16×2 Character LCD

Interfacing AVR to LCD in 4 Bit Mode  Fig shows the interfacing of AVR to LCD in 4 bit mode. 4 bit mode is used in order to save LCD pins. In 4 bit mode data is first sent on the higher nibble and then the lower nibble.

I nterfacing AVR to LCD in 4 Bit Mode using Single PORT  Fig shows the interfacing of AVR to LCD in 4 bit mode using single PORT D.

 Advantages of LCDs:  Consumes less power and generates less heat Saves lot of space compared picture tubes due to LCD's flatness.  Due to less weight and flatness LCDs are highly portable.  No flicker and less screen glare in LCDs to reduce eyestrain.  Disadvantages of LCDs:  LCDs cannot form multiple resolution images.  The contrast ratio for LCD images is lesser than CRT and plasma displays.  Due to their longer response time, LCDs show ghost images and mixing when images change rapidly.  The narrow viewing angle of an LCD weakens the image quality in wider viewing angles.

APPLICATIONS:-  Computer monitors  Televisions  Instrument panels  Cathode ray tube(CRT)  Calculator  Plasma displays  Clocks  watches