change(display): Sleep display when backlight is off

This saves about 1 mA when the display is off.

Not sure if we need to adapt documentation for this. Users will unlikely notice any change.

lib/gfx/LCD/LCD_Driver.c

@@ -54,6 +54,13 @@ parameter	:
 *******************************************************************************/
 void LCD_SetBacklight(UWORD Value)
 {
+	// Turn off the display if the backlight is off to save power
+	if (Value > 0) {
+		LCD_Wake();
+	} else {
+		LCD_Sleep();
+	}
+
 	DEV_Set_BL(Value);
 }
 
@@ -88,6 +95,24 @@ void LCD_WriteReg(UBYTE da)
 	//DEV_Digital_Write(DEV_CS_PIN,1);
 }
 
+/******************************************************************************
+function:
+		Turn on display controller
+******************************************************************************/
+void LCD_Wake(void)
+{
+	LCD_WriteReg(0x11); //Sleep exit
+}
+
+/******************************************************************************
+function:
+		Turn off display controller
+******************************************************************************/
+void LCD_Sleep(void)
+{
+	LCD_WriteReg(0x10); //Sleep in
+}
+
 /******************************************************************************
 function:	
 		Common register initialization
@@ -97,7 +122,7 @@ void LCD_Init(void)
 	LCD_Reset();
 
 	//************* Start Initial Sequence **********//
-	LCD_WriteReg(0x11); //Sleep exit
+	LCD_Wake();
 	DEV_Delay_ms(120);
 	LCD_WriteReg(0x21);
 	LCD_WriteReg(0x21);