Can't control LCD 2004 20X4 with I2C module problem

Hello,

I have the LCD 2004 20X4 blue and IIC/I2C Serial Interface Board Module For Arduino LCD1602 LCD2004 Display (http://www.ebay.co.uk/itm/281366957696?_trksid=p2060353.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT)

The problem is i can't get it work, i already buy 2 LCDs and Modules and they do exactly same thing. Address is 0x27 for sure.

I have tried very libraries including https://bitbucket.org/fmalpartida/new-liquidcrystal/wiki/Home The only thing i can do is blink LCD backlight but text is never shown on LCD, i also have tried lots of combinations in fma constructor and still i can't get it to work. Some code will cause lcd fast blink without show anything.

I also tested with this:

//this is for a unlabeled i2c LCD interface board which allows for changing its address

//                    addr, en,rw,rs,d4,d5,d6,d7
LiquidCrystal_I2C lcd(0x27, 2, 1, 0, 4, 5, 6, 7);  // Set the LCD I2C address

// The address pins A0-A2 are pulled high with the three 10k resistors at the bottom of the picture. 
// If the three pads A0-A2 are jumpered, the address is changed to 0x20.

Still doesn't work...

Any suggestions? I'm getting tired of it :(

Does your current code compile?

Reason I ask, is last time I looked at i2c lcd screen, it only took 3 arguments, the address, columns, rows:

LiquidCrystal_I2C lcd(0x27, 20, 4);

Then its usually just a case of

// in setup
lcd.backlight();

// where you need to print:
lcd.print( "BLAH" );

tammytam: Does your current code compile?

Reason I ask, is last time I looked at i2c lcd screen, it only took 3 arguments, the address, columns, rows:

LiquidCrystal_I2C lcd(0x27, 20, 4);

Then its usually just a case of

// in setup
lcd.backlight();

// where you need to print: lcd.print( "BLAH" );

All codes i have tested compiles well. And yes i tried that too and didnt work... Blacklight on/off works, print doesn't

Don’t get frustrated , just back - off a little and RTFM.

You have I2C LCD which still requires correct assignments to actually interface the I2C “adapter” to Hitachi type of LCD pins, not Arduino pins!

You have to know that for sure , not just “try this constructor or that one” .

There is a difference between backlight and character intensity, they can be controlled by software or hardware, again depending on the I2C interface on the LCD module.

What Vaclav is attempting to explain is that the I2C LCD adapter is actually what is called an I/O expander.
The I/O expander has its own mapping of pins.

This is constructor for the ones I have LiquidCrystal_I2C lcd(0x27, 2, 1, 0, 4, 5, 6, 7, 3, POSITIVE);

AWOL:
What Vaclav is attempting to explain is that the I2C LCD adapter is actually what is called an I/O expander.
The I/O expander has its own mapping of pins.

This is constructor for the ones I have LiquidCrystal_I2C lcd(0x27, 2, 1, 0, 4, 5, 6, 7, 3, POSITIVE);

I know the chip is I/O expander, still i have tried that constructor and didnt work.

UPDATE: After try adjust the knob for contrast it works now :expressionless:
In all pages i have read none said to ajust constrast first, that could save me lot of time :expressionless:
But is solved now.

Thank you all.

There is a difference between backlight and character intensity, they can be controlled by software or hardware, again depending on the I2C interface on the LCD module.

I guess I should have said "if it has a knob, turn it ". I'll try to be more specific next time. Glad you got it working.