LiquidCrystal_I2C.h

#ifndef FDB_LIQUID_CRYSTAL_I2C_H
#define FDB_LIQUID_CRYSTAL_I2C_H

#include <inttypes.h>
#include <Print.h>

// commands
#define LCD_CLEARDISPLAY 0x01
#define LCD_RETURNHOME 0x02
#define LCD_ENTRYMODESET 0x04
#define LCD_DISPLAYCONTROL 0x08
#define LCD_CURSORSHIFT 0x10
#define LCD_FUNCTIONSET 0x20
#define LCD_SETCGRAMADDR 0x40
#define LCD_SETDDRAMADDR 0x80

// flags for display entry mode
#define LCD_ENTRYRIGHT 0x00
#define LCD_ENTRYLEFT 0x02
#define LCD_ENTRYSHIFTINCREMENT 0x01
#define LCD_ENTRYSHIFTDECREMENT 0x00

// flags for display on/off control
#define LCD_DISPLAYON 0x04
#define LCD_DISPLAYOFF 0x00
#define LCD_CURSORON 0x02
#define LCD_CURSOROFF 0x00
#define LCD_BLINKON 0x01
#define LCD_BLINKOFF 0x00

// flags for display/cursor shift
#define LCD_DISPLAYMOVE 0x08
#define LCD_CURSORMOVE 0x00
#define LCD_MOVERIGHT 0x04
#define LCD_MOVELEFT 0x00

// flags for function set
#define LCD_8BITMODE 0x10
#define LCD_4BITMODE 0x00
#define LCD_2LINE 0x08
#define LCD_1LINE 0x00
#define LCD_5x10DOTS 0x04
#define LCD_5x8DOTS 0x00

// flags for backlight control
#define LCD_BACKLIGHT 0x08
#define LCD_NOBACKLIGHT 0x00

#define En B00000100  // Enable bit
#define Rw B00000010  // Read/Write bit
#define Rs B00000001  // Register select bit

/**
   This is the driver for the Liquid Crystal LCD displays that use the I2C bus.

   After creating an instance of this class, first call begin() before anything else.
   The backlight is on by default, since that is the most likely operating mode in
   most cases.
*/
class LiquidCrystal_I2C : public Print {
  public:
    /**
       Constructor

       @param lcd_addr	I2C slave address of the LCD display. Most likely printed on the
     					LCD circuit board, or look in the supplied LCD documentation.
       @param lcd_cols	Number of columns your LCD display has.
       @param lcd_rows	Number of rows your LCD display has.
       @param charsize	The size in dots that the display has, use LCD_5x10DOTS or LCD_5x8DOTS.
    */
    LiquidCrystal_I2C(uint8_t lcd_addr, uint8_t lcd_cols, uint8_t lcd_rows, uint8_t charsize = LCD_5x8DOTS);

    /**
       Set the LCD display in the correct begin state, must be called before anything else is done.
    */
    void begin();

    /**
       Remove all the characters currently shown. Next print/write operation will start
       from the first position on LCD display.
    */
    void clear();

    /**
       Next print/write operation will will start from the first position on the LCD display.
    */
    void home();

    /**
       Do not show any characters on the LCD display. Backlight state will remain unchanged.
       Also all characters written on the display will return, when the display in enabled again.
    */
    void noDisplay();

    /**
       Show the characters on the LCD display, this is the normal behaviour. This method should
       only be used after noDisplay() has been used.
    */
    void display();

    /**
       Do not blink the cursor indicator.
    */
    void noBlink();

    /**
       Start blinking the cursor indicator.
    */
    void blink();

    /**
       Do not show a cursor indicator.
    */
    void noCursor();

    /**
       Show a cursor indicator, cursor can blink on not blink. Use the
       methods blink() and noBlink() for changing cursor blink.
    */
    void cursor();

    void scrollDisplayLeft();
    void scrollDisplayRight();
    void printLeft();
    void printRight();
    void leftToRight();
    void rightToLeft();
    void shiftIncrement();
    void shiftDecrement();
    void noBacklight();
    void backlight();
    bool getBacklight();
    void autoscroll();
    void noAutoscroll();
    void createChar(uint8_t, uint8_t[]);
    void setCursor(uint8_t, uint8_t);
    virtual size_t write(uint8_t);
    void command(uint8_t);

    inline void blink_on() {
      blink();
    }
    inline void blink_off() {
      noBlink();
    }
    inline void cursor_on() {
      cursor();
    }
    inline void cursor_off() {
      noCursor();
    }

    // Compatibility API function aliases
    void setBacklight(uint8_t new_val);				// alias for backlight() and nobacklight()
    void load_custom_character(uint8_t char_num, uint8_t *rows);	// alias for createChar()
    void printstr(const char[]);

  private:
    void send(uint8_t, uint8_t);
    void write4bits(uint8_t);
    void expanderWrite(uint8_t);
    void pulseEnable(uint8_t);
    uint8_t _addr;
    uint8_t _displayfunction;
    uint8_t _displaycontrol;
    uint8_t _displaymode;
    uint8_t _cols;
    uint8_t _rows;
    uint8_t _charsize;
    uint8_t _backlightval;
};

#endif // FDB_LIQUID_CRYSTAL_I2C_H

LiquidCrystal_I2C.cpp

#include "LiquidCrystal_I2C.h"
#include <inttypes.h>
#include <Arduino.h>
#include <Wire.h>

// When the display powers up, it is configured as follows:
//
// 1. Display clear
// 2. Function set:
//    DL = 1; 8-bit interface data
//    N = 0; 1-line display
//    F = 0; 5x8 dot character font
// 3. Display on/off control:
//    D = 0; Display off
//    C = 0; Cursor off
//    B = 0; Blinking off
// 4. Entry mode set:
//    I/D = 1; Increment by 1
//    S = 0; No shift
//
// Note, however, that resetting the Arduino doesn't reset the LCD, so we
// can't assume that its in that state when a sketch starts (and the
// LiquidCrystal constructor is called).

LiquidCrystal_I2C::LiquidCrystal_I2C(uint8_t lcd_addr, uint8_t lcd_cols, uint8_t lcd_rows, uint8_t charsize)
{
  _addr = lcd_addr;
  _cols = lcd_cols;
  _rows = lcd_rows;
  _charsize = charsize;
  _backlightval = LCD_BACKLIGHT;
}

void LiquidCrystal_I2C::begin() {
  Wire.begin();
  _displayfunction = LCD_4BITMODE | LCD_1LINE | LCD_5x8DOTS;

  if (_rows > 1) {
    _displayfunction |= LCD_2LINE;
  }

  // for some 1 line displays you can select a 10 pixel high font
  if ((_charsize != 0) && (_rows == 1)) {
    _displayfunction |= LCD_5x10DOTS;
  }

  // SEE PAGE 45/46 FOR INITIALIZATION SPECIFICATION!
  // according to datasheet, we need at least 40ms after power rises above 2.7V
  // before sending commands. Arduino can turn on way befer 4.5V so we'll wait 50
  delay(50);

  // Now we pull both RS and R/W low to begin commands
  expanderWrite(_backlightval);	// reset expanderand turn backlight off (Bit 8 =1)
  delay(1000);

  //put the LCD into 4 bit mode
  // this is according to the hitachi HD44780 datasheet
  // figure 24, pg 46

  // we start in 8bit mode, try to set 4 bit mode
  write4bits(0x03 << 4);
  delayMicroseconds(4500); // wait min 4.1ms

  // second try
  write4bits(0x03 << 4);
  delayMicroseconds(4500); // wait min 4.1ms

  // third go!
  write4bits(0x03 << 4);
  delayMicroseconds(150);

  // finally, set to 4-bit interface
  write4bits(0x02 << 4);

  // set # lines, font size, etc.
  command(LCD_FUNCTIONSET | _displayfunction);

  // turn the display on with no cursor or blinking default
  _displaycontrol = LCD_DISPLAYON | LCD_CURSOROFF | LCD_BLINKOFF;
  display();

  // clear it off
  clear();

  // Initialize to default text direction (for roman languages)
  _displaymode = LCD_ENTRYLEFT | LCD_ENTRYSHIFTDECREMENT;

  // set the entry mode
  command(LCD_ENTRYMODESET | _displaymode);

  home();
}

/********** high level commands, for the user! */
void LiquidCrystal_I2C::clear() {
  command(LCD_CLEARDISPLAY);// clear display, set cursor position to zero
  delayMicroseconds(2000);  // this command takes a long time!
}

void LiquidCrystal_I2C::home() {
  command(LCD_RETURNHOME);  // set cursor position to zero
  delayMicroseconds(2000);  // this command takes a long time!
}

void LiquidCrystal_I2C::setCursor(uint8_t col, uint8_t row) {
  int row_offsets[] = { 0x00, 0x40, 0x14, 0x54 };
  if (row > _rows) {
    row = _rows - 1;  // we count rows starting w/0
  }
  command(LCD_SETDDRAMADDR | (col + row_offsets[row]));
}

// Turn the display on/off (quickly)
void LiquidCrystal_I2C::noDisplay() {
  _displaycontrol &= ~LCD_DISPLAYON;
  command(LCD_DISPLAYCONTROL | _displaycontrol);
}
void LiquidCrystal_I2C::display() {
  _displaycontrol |= LCD_DISPLAYON;
  command(LCD_DISPLAYCONTROL | _displaycontrol);
}

// Turns the underline cursor on/off
void LiquidCrystal_I2C::noCursor() {
  _displaycontrol &= ~LCD_CURSORON;
  command(LCD_DISPLAYCONTROL | _displaycontrol);
}
void LiquidCrystal_I2C::cursor() {
  _displaycontrol |= LCD_CURSORON;
  command(LCD_DISPLAYCONTROL | _displaycontrol);
}

// Turn on and off the blinking cursor
void LiquidCrystal_I2C::noBlink() {
  _displaycontrol &= ~LCD_BLINKON;
  command(LCD_DISPLAYCONTROL | _displaycontrol);
}
void LiquidCrystal_I2C::blink() {
  _displaycontrol |= LCD_BLINKON;
  command(LCD_DISPLAYCONTROL | _displaycontrol);
}

// These commands scroll the display without changing the RAM
void LiquidCrystal_I2C::scrollDisplayLeft(void) {
  command(LCD_CURSORSHIFT | LCD_DISPLAYMOVE | LCD_MOVELEFT);
}
void LiquidCrystal_I2C::scrollDisplayRight(void) {
  command(LCD_CURSORSHIFT | LCD_DISPLAYMOVE | LCD_MOVERIGHT);
}

// This is for text that flows Left to Right
void LiquidCrystal_I2C::leftToRight(void) {
  _displaymode |= LCD_ENTRYLEFT;
  command(LCD_ENTRYMODESET | _displaymode);
}

// This is for text that flows Right to Left
void LiquidCrystal_I2C::rightToLeft(void) {
  _displaymode &= ~LCD_ENTRYLEFT;
  command(LCD_ENTRYMODESET | _displaymode);
}

// This will 'right justify' text from the cursor
void LiquidCrystal_I2C::autoscroll(void) {
  _displaymode |= LCD_ENTRYSHIFTINCREMENT;
  command(LCD_ENTRYMODESET | _displaymode);
}

// This will 'left justify' text from the cursor
void LiquidCrystal_I2C::noAutoscroll(void) {
  _displaymode &= ~LCD_ENTRYSHIFTINCREMENT;
  command(LCD_ENTRYMODESET | _displaymode);
}

// Allows us to fill the first 8 CGRAM locations
// with custom characters
void LiquidCrystal_I2C::createChar(uint8_t location, uint8_t charmap[]) {
  location &= 0x7; // we only have 8 locations 0-7
  command(LCD_SETCGRAMADDR | (location << 3));
  for (int i = 0; i < 8; i++) {
    write(charmap[i]);
  }
}

// Turn the (optional) backlight off/on
void LiquidCrystal_I2C::noBacklight(void) {
  _backlightval = LCD_NOBACKLIGHT;
  expanderWrite(0);
}

void LiquidCrystal_I2C::backlight(void) {
  _backlightval = LCD_BACKLIGHT;
  expanderWrite(0);
}
bool LiquidCrystal_I2C::getBacklight() {
  return _backlightval == LCD_BACKLIGHT;
}


/*********** mid level commands, for sending data/cmds */

inline void LiquidCrystal_I2C::command(uint8_t value) {
  send(value, 0);
}

inline size_t LiquidCrystal_I2C::write(uint8_t value) {
  send(value, Rs);
  return 1;
}


/************ low level data pushing commands **********/

// write either command or data
void LiquidCrystal_I2C::send(uint8_t value, uint8_t mode) {
  uint8_t highnib = value & 0xf0;
  uint8_t lownib = (value << 4) & 0xf0;
  write4bits((highnib) | mode);
  write4bits((lownib) | mode);
}

void LiquidCrystal_I2C::write4bits(uint8_t value) {
  expanderWrite(value);
  pulseEnable(value);
}

void LiquidCrystal_I2C::expanderWrite(uint8_t _data) {
  Wire.beginTransmission(_addr);
  Wire.write((int)(_data) | _backlightval);
  Wire.endTransmission();
}

void LiquidCrystal_I2C::pulseEnable(uint8_t _data) {
  expanderWrite(_data | En);	// En high
  delayMicroseconds(1);		// enable pulse must be >450ns

  expanderWrite(_data & ~En);	// En low
  delayMicroseconds(50);		// commands need > 37us to settle
}

void LiquidCrystal_I2C::load_custom_character(uint8_t char_num, uint8_t *rows) {
  createChar(char_num, rows);
}

void LiquidCrystal_I2C::setBacklight(uint8_t new_val) {
  if (new_val) {
    backlight();		// turn backlight on
  } else {
    noBacklight();		// turn backlight off
  }
}

void LiquidCrystal_I2C::printstr(const char c[]) {
  //This function is not identical to the function used for "real" I2C displays
  //it's here so the user sketch doesn't have to be changed
  print(c);
}