LCD 16x02-IC2 dont work... Yes I google first...Help !!!

So, this is a very common thing to do, never the least it gone terribly wrong for me.

LDC.- QC1602A V.2.0 DataSheetLCD
IC2- IIC-I2C-TWI-SP-Serial This One
Arduino UNO R3.

So… I instal Malpartida librarys.
Run the IC2 scanner…
I2C scanner. Scanning …
Found address: 39 (0x27)
Done.
Found 1 device(s).

So… I use the data sheet for re-pin the sketch as follows…

/* 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(0x27, 6, 5, 4, 11, 12, 13, 14, 15, NEGATIVE);  // 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 ) */

The LCD don do anything… I leave the jumper for the backligth and when the sketch is loaded and start to run… tur off the backligth and not on again… Until I manually disconnect the usb arduino and re-conect…

I solder the adpater as in here… according to the Vss Vdd of the datasheet of the display…
As in here Exact same LCD and adaptor…

I conect the SDA to A4
and SCL to A5

I see something odd. At least to me in the code;

EN, RW, RS, D4, D5, D6, D7 ,BL, BLPOL
6,    5,    4,  11, 12 ,13, 14  (16, NEGATIVE )

The data-sheed says;
PIN - Symbol - Description
15 A/Vee +4.2 for LED, negative output
16 K Power supply for B/L (0V)

So… Im a litte confused whath to do here… is the Bak ligth pin… 15, or 16… and even…
it is positive or negative… 15 Pins says negative-output… ???¡?¡

So I ran the next test on the display;
EN, RW, RS, D4, D5, D6, D7 ,BL, BLPOL
6, 5, 4, 11, 12 ,13, 14 (16, NEGATIVE )
(15, POSITIVE)
(16, POSITIVE)
(15, NEGATIVE)

None of the cases works… :disappointed_relieved: :disappointed_relieved: :disappointed_relieved:

Any ideas’???
I try several more sketch for run the LCD…
The lcd stays on… if i remove the SDA and SCL wires, as soon gets conected and the arduino rebooted… the lcd turn off And it has to be manually unpluged from the arduino and re-conected…

Any one can adress me in the rigth direction?

Kind Regards.
-Alex.

LiquidCrystal_I2C lcd(0x27, 6, 5, 4, 11, 12, 13, 14, 15, NEGATIVE);

This line is known as the "constructor", and it is not right for your backpack.

An easy way to determine the correct constructor is to run Bill Perry's i2cLCDguesser sketch which can be found here http://forum.arduino.cc//index.php?topic=157817.msg1235230#msg1235230

I have run the sketch you posted with my lcd and it's constructor and it runs as designed.

cattledog: LiquidCrystal_I2C lcd(0x27, 6, 5, 4, 11, 12, 13, 14, 15, NEGATIVE);

This line is known as the "constructor", and it is not right for your backpack.

An easy way to determine the correct constructor is to run Bill Perry's i2cLCDguesser sketch which can be found here http://forum.arduino.cc//index.php?topic=157817.msg1235230#msg1235230

I have run the sketch you posted with my lcd and it's constructor and it runs as designed.

Thank you so much!!!!!

Now its working... I will save this in my toolbox!!!

Again... Thank you so much!!!! :D :D :D :D