20x4 I2C beginner

Other Hardware Displays
1

I bought this LCD screen.
And I got this I2C module.
I downloaded NewliquidCrystal_1.3.4.zip

My code is as follows:

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

LiquidCrystal_I2C lcd(0x3F, 2, 1, 0, 4, 5, 6, 7, 3, POSITIVE);  

void setup()  
{
//  Serial.begin(9600);  // Used to type in characters
  lcd.begin(20,4);     // initialize the lcd for 20 chars 4 lines and turn on backlight

for(int i = 0; i< 3; i++)
  {
    lcd.backlight();
    delay(250);
    lcd.noBacklight();
    delay(250);
  }
  lcd.backlight(); 


  lcd.setCursor(3,0); 
  lcd.print("Hello, World!");
  delay(1000);
  lcd.setCursor(0,1);
  lcd.print("This is a test");
  delay(1000);  
  lcd.setCursor(0,2);
  lcd.print("   I2C   ");
  lcd.setCursor(0,3);
  delay(1000);   
  lcd.print("Testing Testing");


}


void loop()  
{
  {
   
  }

}

I know the address is correct, because the for loop executes (the screen flashes 3 times).

The rest of the code does not work, as I only get 2 lines of white blocks (see the pic).

Any help will be much appreciated, as I am very new to this.

2

Here is the pic

20160207_090512r.jpg
20160207_090512r.jpg1240×930 310 KB

3

Backpacks are normally soldered to the back of the display.

The photo looks as if your soldering is 'ok'.
We cannot see the quality of your soldering between the backpack and display.

David.

4

It actually wasn't soldered, just pushed through the holes.
So I soldered it, and now it's working!!

Thank you David!

5

As usual!

6

Paul__B:
As usual!

Didn't know that.
Important lesson learned I guess.

7

Yes, it comes up here so often!

8

This is the sketch we use to test our LCDs. You can use it to give you an idea how to work with it and modify to fit your needds

This sketch will display a series of numbers 0-44 on a LCD screen 20x4 filling each line with consecutive numbers until it reaches the end and then it starts again.

/*
 This sketch will display a series of numbers 0-44 on a LCD screen 20x4 filling each line with consecutive numbers until it reaches
 the end and then it starts again. 
 
 Code used for learning purposes developed by: www.HackerspaceLA.org | @hackerspacela 
 Code modified from Adafruit at: https://www.arduino.cc/en/Tutorial/LiquidCrystalAutoscroll
 This example code is in the public domain: http://www.arduino.cc/en/Tutorial/LiquidCrystalAutoscroll
 */
 // include the library code:
#include <Wire.h>
#include <LiquidCrystal_I2C.h>

//#define pins:

#define I2C_ADDR    0x27 // LCD address (make sure you run the I2C scanner to verify our LCD address)
#define Rs_pin  0        // Assign pins between I2C and LCD
#define Rw_pin  1
#define En_pin  2
#define BACKLIGHT_PIN 3
#define D4_pin  4
#define D5_pin  5
#define D6_pin  6
#define D7_pin  7

LiquidCrystal_I2C lcd(I2C_ADDR,En_pin,Rw_pin,Rs_pin,D4_pin,D5_pin,D6_pin,D7_pin);


// initialize the library with the numbers of the interface pins

void setup() {
  // set up backlight and turn on module:
lcd.setBacklightPin(BACKLIGHT_PIN,POSITIVE);
lcd.setBacklight(HIGH);
  // set up the LCD's number of columns and rows:
lcd.begin(20, 4); //My LCD is 20x4
}

void loop() {
  // set the cursor to (0, 0) on line #1
  lcd.setCursor (0, 0);
  //lcd.autoscroll();
  // print from 0 to 14:
  for (int thisChar = 0; thisChar < 15; thisChar++) {
    lcd.print(thisChar);
    lcd.leftToRight();
    delay(500);
  }

  // set the cursor to (0, 1) on line #2
  lcd.setCursor (0, 1);
  // set the display to automatically scroll:
  //lcd.autoscroll();
  // print from 0 to 14:
  for (int thisChar = 15; thisChar < 25; thisChar++) {
    lcd.print(thisChar);
    delay(500);
  }

    // set the cursor to (0, 1) on line #3
  lcd.setCursor (0, 2);
  // set the display to automatically scroll:
  //lcd.autoscroll();
  // print from 0 to 14:
  for (int thisChar = 25; thisChar < 35; thisChar++) {
    lcd.print(thisChar);
    delay(500);
  }

    // set the cursor to (0, 1) on line #4
  lcd.setCursor (0, 3);
  // set the display to automatically scroll:
  //lcd.autoscroll();
  // print from 0 to 14:
  for (int thisChar = 35; thisChar < 45; thisChar++) {
    lcd.print(thisChar);
    delay(500);
  }
    
  // turn off automatic scrolling
  lcd.noAutoscroll();

  // clear screen for the next loop:
  lcd.clear();
}

See example in action here: https://goo.gl/photos/yqhsG5i93vbi22qa7

Double check this part: LiquidCrystal_I2C lcd(I2C_ADDR,En_pin,Rw_pin,Rs_pin,D4_pin,D5_pin,D6_pin,D7_pin);