Added backlight control through library.

LiquidCrystal.cpp

@@ -217,5 +217,6 @@ void LiquidCrystal::setBacklight ( uint8_t mode )
 // setBacklightPin
 void LiquidCrystal::setBacklightPin ( uint8_t pin )
 {
+   pinMode ( pin, OUTPUT ); // Difine the backlight pin as output
    _backlightPin = pin;
 }

LiquidCrystal_I2C.cpp

@@ -122,6 +122,8 @@ void LiquidCrystal_I2C::begin(uint8_t cols, uint8_t lines, uint8_t dotsize)
 //----------------------------------------------------------------------------
 
 // Turn the (optional) backlight off/on
+//
+// setBacklight
 void LiquidCrystal_I2C::setBacklight( uint8_t mode ) 
 {
    if ( mode == HIGH )
@@ -136,6 +138,8 @@ void LiquidCrystal_I2C::setBacklight( uint8_t mode )
    _i2cio.write( _backlightMask );
 }
 
+//
+// setBacklightPin
 void LiquidCrystal_I2C::setBacklightPin ( uint8_t pin )
 {
    _backlightPin = ( 1 << pin );

examples/HelloWorld_4bit/HelloWorld_4bit.ino

@@ -5,7 +5,7 @@
 LiquidCrystal lcd(12, 11, 5, 4, 3, 2);
 #define   CONTRAST_PIN   9
 #define   BACKLIGHT_PIN  7
-#define   CONTRAST       100
+#define   CONTRAST       110
 
 // Creat a set of new characters
 byte smiley[8] = {
@@ -47,10 +47,10 @@ void setup()
 
   // Switch on the backlight and LCD contrast levels
   pinMode(CONTRAST_PIN, OUTPUT);
-  pinMode(BACKLIGHT_PIN, OUTPUT);
+  analogWrite ( CONTRAST_PIN, CONTRAST );
 
-  digitalWrite(BACKLIGHT_PIN, HIGH);
-  analogWrite (CONTRAST_PIN, CONTRAST);
+  lcd.setBacklightPin ( BACKLIGHT_PIN );
+  lcd.setBacklight ( HIGH );
     
   lcd.begin(16,2);               // initialize the lcd