LCD 1602 I2C to LCD wont display

I am trying to use a 20x4 JHD 204A LCd with an LCD 1602 I2C adapter without success. I have uploaded the following code:

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

LiquidCrystal_I2C lcd(0x27, 20, 4);

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

void loop()

The default call address is supposed to be 0x27, which I have changed the code to include (as above), but I’m still getting nothing on the display. I have the backlight jumper on the adapter board connected. Is there something obvious that I’m missing here? Thanks.

There is i2c scanner code out there, load that and check the output to see if you are set for 0x027. Do you see the squares in the first and third row.?? If not adjust the contrast pot (most adapters have them). If you have the same lib that I downloaded there is an examples directory with a 'hello world' that should get you started. I also did not see an lcd.begin in your code. That library works well, I was able to connect 3 displays and send what I wanted to each. Good Luck.

Your descriptor "lcd(0x27, 20, 4)" is incorrect (obsolete library).

You need to be using the fmalpartida library (removing the useless original LiquidCrystal library) and then run the I2Cguesser code in order to find your correct descriptor which you then have to put in the code.

And you have to have SDA and SCL connected to the correct pins.