A lean, high speed I2C LCD Library for Arduino, which supports MCP23008 and MCP23017
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A lean, high speed I2C LCD Library for Arduino, which supports MCP23008 (Adafruit LCD Backpack) and MCP23017 (Adafruit RGB LCD Shield)

hacked by Sam C. Lin / http://www.lincomatic.com
  LiquidTWI by Matt Falcon (FalconFour) / http://falconfour.com
  logic gleaned from Adafruit RGB LCD Shield library
  Panelolu2 support by Tony Lock / http://blog.think3dprint3d.com
  Panelolu2 integration by Robert F-C / https://github.com/buildrob
  enhancements by Nick Sayer / https://github.com/nsayer

Compatible with Adafruit I2C LCD backpack (MCP23008) and
Adafruit RGB LCD Shield (and optionally, Panelolu2)

For more information see 
 Panelolu2 usage see

  Version 1.2.6


  * 1.2.6 / 20140220 SCL
  added device detected guard to home() & buzz()

  * 1.2.5 / 20130725 SCL
  added LcdDetected() from Scott Rubin

  * 1.2.4 / 20130409 SCL
  buzz() fixes from buildrob

  * 1.2.3 / 20130322 SCL
  PANELOLU2 support cleanup and always enabled when MCP23017 by buildrob
  buzz() now works for Panucatt Viki as well

  * 1.2.2 / 20130120 SCL
  make setMCPType() a no-op when only one MCPxxxx defined instead
  of removing it

  * 1.2.1 / 20130102 SCL
  disable PANELOLU2 by default

  * 1.2.0 / 20130101 SCL

  * 1.1.1 / 20121219 SCL
  added Tony Lock's Panelolu2 enhancements

  * 1.1.0 / 20121018 SCL
  use 8-bit GPIO for writing on MCP23017 for 25% speed increase
  with only 14 byte size increase

  * 1.0.0 / 20121016 SCL
  initial release

  Distributed with as free-will a license as is available given this code's long
  associative chain of licenses (LiquidCrystal -> Arduino -> Wiring -> ...?). Use
  it in any way you feel fit, profit or free, provided it fits in the licenses of
  its associated works.

  extract LiquidTWI2/ into <arduinosketchbook>/libraries/LiquidTWI2

  To use with Panelolu2
    Panelolu2 only has encoder.. use PANELOLU_ENCODER_X bits instead of BUTTON_xxx

  Compatible with Arduino LiquidCrystal library except that setMCPType() MUST
  be called at least once before begin() is called

  // MCP23008 (Adafruit LCD Backpack)
  #include <Wire.h>
  #include <LiquidTWI2.h>
  LiquidTWI2 lcd(0x20);
  void setup() {
   lcd.setMCPType(LTI_TYPE_MCP23008); // must be called before begin()
   lcd.setBacklight(HIGH); // only supports HIGH or LOW
  void loop() {
   lcd.print("Hello World!");

  // MCP23017 (Adafruit RGB LCD Shield)
  #include <Wire.h>
  #include <LiquidTWI2.h>
  LiquidTWI2 lcd(0x20);
  void setup() {
   lcd.setMCPType(LTI_TYPE_MCP23017); // must be called before begin()
   lcd.setBacklight(WHITE); // see LiquidTWI2.h for color options
  void loop() {
   lcd.print("Hello World!");
   uint8_t btns = lcd.readButtons();

  If you change the i2c address of the board, set "lcd(0x20)" to your new 3-bit
  If you have more than a 16x2 LCD, change "lcd.begin(16,2)" to reflect the
  columns and rows of your LCD.

  Normally, the code will hang if the device is not detected at the specified
  i2c address.  If you want to compile your code for an optionally installed
  LCD, call the constructor with 2nd parameter deviceDetect=1. E.g:
     LiquidTWI2 lcd(0x20,1);
  When enabled, if the device is not detected at the specified address when
  begin() is called, then the rest of the function calls become NOOPs

  Note that the library can switch modes at runtime. Simply call setMCPType(),
  followed by begin().
  This allows you to create a firmware which is compatible with either kind
  of LCD module, and select the type from EEPROM.

  For memory-constrained projects, disable the unnecessary support by
  commenting out the corresponding MCP230xx in LiquidTWI2.h, and DETECT_DEVICE