4 x 20 LCD with I2C Backpack displaying 2 rows of White Blocks

Serial Interface:

LCD

I'm using the suggested library: http://hmario.home.xs4all.nl/arduino/LiquidCrystal_I2C/LiquidCrystal_I2C.zip

But the Hello World example is only giving me rows of solid white blocks on rows 1 and 3. Address has been confirmed as 0x27 by I2C scanner script.

Anyone know what might be going on?

Your display is internally set up as 2 lines of 80 characters. The first line will show these blocks if the LCD is not or incorrect initialised. So exactly what you see.

To be able to tell you more, show your code (in code tags please (click the # button above the edit box)), you're probably skipping a step.

There was a large discussion about these boards.

Lets make it short - try this code as it is:

/* YourDuino.com Example Software Sketch
 20 character 4 line I2C Display
 Backpack Interface labelled "LCM1602 IIC  A0 A1 A2"
 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 )-----*/
//none
/*-----( 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, 2, 1, 0, 4, 5, 6, 7, 3, POSITIVE);  // Set the LCD I2C address


/*-----( Declare Variables )-----*/
//none

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

  lcd.begin(20,4);         // initialize the lcd for 20 chars 4 lines and 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(3,0); //Start at character 4 on line 0
  lcd.print("Hello, world!");
  delay(1000);
  lcd.setCursor(2,1);
  lcd.print("From YourDuino");
  delay(1000);  
  lcd.setCursor(0,2);
  lcd.print("20 by 4 Line Display");
  lcd.setCursor(0,3);
  delay(2000);   
  lcd.print("http://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.setCursor(0,0); //Start at character 0 on line 0
  lcd.print("Start Serial Monitor");
  lcd.setCursor(0,1);
  lcd.print("Type chars 2 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 ) */

MAS3:
Your display is internally set up as 2 lines of 80 characters.
The first line will show these blocks if the LCD is not or incorrect initialised.
So exactly what you see.

To be able to tell you more, show your code (in code tags please (click the # button above the edit box)), you’re probably skipping a step.

Thanks for the reply. This is the Hello World example I’m using from the liquidcrystal_i2c library. All I did was modify the address and rows/lines.

#include <Wire.h> 
#include <LiquidCrystal_I2C.h>

LiquidCrystal_I2C lcd(0x27,20,4);  // set the LCD address to 0x20 for a 16 chars and 2 line display

void setup()
{
  lcd.init();                      // initialize the lcd 
 
  // Print a message to the LCD.
  lcd.backlight();
  lcd.print("Hello, world!");
}

void loop()
{
}

A.R.Ty: There was a large discussion about these boards.

Lets make it short - try this code as it is:

Thank you! I had tried that previously and it failed because I didn't notice this:

// Move any other LCD libraries to another folder or delete them

Works great now. :)

Library: https://bitbucket.org/fmalpartida/new-liquidcrystal/downloads

So, all is fine - enjoy your display XD