Notes About PCF8574 I2C LCD Using LiquidCrystal_I2C.h

IC Manufacturer
NXP - PCF8574P, PCF8574AP
TI - PCF8574N

Library
LiquidCrystal_I2C.h by Francisco Malpartida download from BitBucket Repository

Address
I2C address of PC8574 (all three address inputs grounded) = 0x20
I2C address of PC8574A (all three address inputs grounded) = 0x38

Pins Mapping (16 Pins 8574) (Schematic)
PCF8574.Pin1 -> GND
PCF8574.Pin2 -> GND
PCF8574.Pin3 -> GND
PCF8574.Pin4 (Port0) -> LCD.Pin11 (DB4)
PCF8574.Pin5 (Port1) -> LCD.Pin12 (DB5)
PCF8574.Pin6 (Port2) -> LCD.Pin13 (DB6)
PCF8574.Pin7 (Port3) -> LCD.Pin14 (DB7)
PCF8574.Pin9 (Port4) -> LCD.Pin4 (RS)
PCF8574.Pin10 (Port5) -> LCD.Pin5 (WR)
PCF8574.Pin11 (Port6) -> LCD.Pin6 (EN)
PCF8574.Pin14 (SCL) -> UNO.A5
PCF8574.Pin15 (SDA) -> UNO.A4
PCF8574.Pin16 (VDD) -> UNO.5V
PCF8574.Pin8 (VSS) -> UNO.GND

LCD Initialization
#include <Wire.h> // comes with Arduino IDE
#include <LiquidCrystal_I2C.h>
LiquidCrystal_I2C lcd(0x20)
lcd.begin(16,2) // in Setup()

Variations (Yourduino)
   Marked "YwRobot Arduino LCM1602 IIC V1" -> lcd.begin(0x27, 2, 1, 0, 4, 5, 6, 7, 3, POSITIVE) // also SainSmart LCD2004, DFRobot (DZRMO)
   Marked "Arduino-IIC-LCD GY-LCD-V1" -> lcd.begin(0x20, 4, 5, 6, 0, 1, 2, 3, 7, NEGATIVE)
   Marked "LCD1602 IIC A0 A1 A2" -> lcd.begin(0x20, 2, 1, 0, 4, 5, 6, 7, 3, POSITIVE)

Example Code (Yourduino)
/* YourDuino.com Example Software Sketch
 16 character 2 line I2C Display
 Backpack Interface labelled "YwRobot Arduino LCM1602 IIC V1"
 terry@yourduino.com */

/*-----( Import needed libraries )-----*/
#include <Wire.h>  // Comes with Arduino IDE
// Get the LCD I2C Library here: 
// https://bitbucket.org/fmalpartida/new-liquidcrystal/downloads
// Move any other LCD libraries to another folder or delete them
// See Library "Docs" folder for possible commands etc.
#include <LiquidCrystal_I2C.h>

/*-----( Declare Constants )-----*/
/*-----( Declare objects )-----*/
// set the LCD address to 0x27 for a 20 chars 4 line display
// Set the pins on the I2C chip used for LCD connections:
//                    addr, en,rw,rs,d4,d5,d6,d7,bl,blpol
LiquidCrystal_I2C lcd(0x20);  // Set the LCD I2C address

/*-----( Declare Variables )-----*/
//NONE

void setup()   /*----( SETUP: RUNS ONCE )----*/
{
  Serial.begin(9600);  // Used to type in characters

  lcd.begin(16,2);   // initialize the lcd for 16 chars 2 lines, turn on backlight

// ------- Quick 3 blinks of backlight  -------------
  for(int i = 0; i< 3; i++)
  {
    lcd.backlight();
    delay(250);
    lcd.noBacklight();
    delay(250);
  }
  lcd.backlight(); // finish with backlight on  

//-------- Write characters on the display ------------------
// NOTE: Cursor Position: (CHAR, LINE) start at 0  
  lcd.setCursor(0,0); //Start at character 4 on line 0
  lcd.print("Hello, world!");
  delay(1000);
  lcd.setCursor(0,1);
  lcd.print("HI!YourDuino.com");
  delay(8000);  

// Wait and then tell user they can start the Serial Monitor and type in characters to
// Display. (Set Serial Monitor option to "No Line Ending")
  lcd.clear();
  lcd.setCursor(0,0); //Start at character 0 on line 0
  lcd.print("Use Serial Mon");
  lcd.setCursor(0,1);
  lcd.print("Type to display");  


}/*--(end setup )---*/


void loop()   /*----( LOOP: RUNS CONSTANTLY )----*/
{
  {
    // when characters arrive over the serial port...
    if (Serial.available()) {
      // wait a bit for the entire message to arrive
      delay(100);
      // clear the screen
      lcd.clear();
      // read all the available characters
      while (Serial.available() > 0) {
        // display each character to the LCD
        lcd.write(Serial.read());
      }
    }
  }

}/* --(end main loop )-- */


/* ( THE END ) */