I2C for LCD

A cheap I2C expander aimed at LCD’s is available from a multitude of sources such as eBay or DealExtreme (http://www.dx.com/p/lcd1602-adapter-board-w-iic-i2c-interface-black-works-with-official-arduino-boards-216865). The pin-out from this interface matches the pin-out from most Hitachi based LCD’s and therefore can easily be connected, just make sure that the pin’s are not connected in reverse.

1	2	3	4	5	6	7	8	9	10	11	12	13	14	15	16
Gnd	Vcc	Vlcd	RS	RW	E	D0	D1	d2	D3	D4	D5	D6	D7	Anod	Cathode

After downloading and installing the library from F. Malpartida, use the following program to test

/*
P4 R/S
P5 RW
P6 E
P0 D4
P1 D5
P2 D6
P3 D7

A4=SDA 
A5=SCL
*/
#include  <Wire.h>
#include  <LiquidCrystal_I2C.h>
#define BACKLIGHT_PIN     3
#define I2C_ADDR 0x27 
LiquidCrystal_I2C lcd(I2C_ADDR, 2, 1, 0, 4, 5, 6, 7, 3, POSITIVE);
// Create a set of new characters
const uint8_t charBitmap[][8] = {
   { 0xc, 0x12, 0x12, 0xc, 0, 0, 0, 0 },
   { 0x6, 0x9, 0x9, 0x6, 0, 0, 0, 0 },
   { 0x0, 0x6, 0x9, 0x9, 0x6, 0, 0, 0x0 },
   { 0x0, 0xc, 0x12, 0x12, 0xc, 0, 0, 0x0 },
   { 0x0, 0x0, 0xc, 0x12, 0x12, 0xc, 0, 0x0 },
   { 0x0, 0x0, 0x6, 0x9, 0x9, 0x6, 0, 0x0 },
   { 0x0, 0x0, 0x0, 0x6, 0x9, 0x9, 0x6, 0x0 },
   { 0x0, 0x0, 0x0, 0xc, 0x12, 0x12, 0xc, 0x0 }
   
};

void setup()
{
   int charBitmapSize = (sizeof(charBitmap ) / sizeof (charBitmap[0]));

    
  lcd.begin(16,2);               // initialize the lcd 
// Switch off the backlight
noBacklight()

   for ( int i = 0; i < charBitmapSize; i++ )
   {
      lcd.createChar ( i, (uint8_t *)charBitmap[i] );
   }

  lcd.home ();                   // go home
  lcd.print("Hello, ARDUINO ");  
  lcd.setCursor ( 0, 1 );        // go to the next line
  lcd.print (" FORUM - fm   ");
  delay ( 1000 );
}

void loop()
{
   lcd.home ();
   // Do a little animation by writing to the same location
   for ( int i = 0; i < 2; i++ )
   {
      for ( int j = 0; j < 16; j++ )
      {
         lcd.print (char(random(7)));
      }
      lcd.setCursor ( 0, 1 );
   }
   delay (200);
}

The standard address on the I2C bus for this model is 27H. In case you need/want to change that, you need to connect the A1-A3 lines to ground: either 1, 2 or all 3 of them. The table below  shows what adresses correspond with what  connections. You will find solderpads  of these addresses on the board.

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