I need some help with the I2C LCD module’s library . The module itself is PCF8574T chip and I can’t find a library that would display text on the LCD. I have checked the address of the I2C (0x27) and the LCD is (1602A). I have tried many libraries such as HD44780 ,and others but none of them worked for me.
Please help me.
- please post a link to the I2C module that you have bought. (PCF8573 is a clock/calendar chip)
- please post a link to the LCD module. e.g. Ebay sale page
- is the I2C module professionally soldered to the LCD module?
- install the "hd44780.h" library via IDE Library Manager.
- run the diagnostic sketch.
hd44780\examples\ioClass\hd44780_I2Cexp\I2CexpDiag\I2CexpDiag.ino - copy-paste the diagnostic output from the Serial Terminal.
We will get you going within minutes. Don't worry about typos. We all make them.
The trick is: confess, and correct the typo. e.g. PCF8574T
David.
What does the display do?
Does the backlight come on?
Are there blocks showing in one or more rows?
Have you tried adjusting the contrast pot?
I agree with @david_prentice that you should install the hd44780 library. You have the best chance of getting the LCD to work with that library as it will automatically detect the I2C address and the pin mapping between the LCD and I2C backpack. Install the hd44870 library and if you still can't get the display to work load and run the I2CexpDiag example and post the results.
path to the diagnostic example:
Post photos of the LCD and wiring, please.
Yeah the chip on the board is PCF8574T.
The I2C is soldered correctly.
When run the diagnostic sketch there are many errors
1.'showSystemConfig' was not declared in this scope
2.'i2cpulluptest' was not declared in this scope
3.'fatalError' was not declared in this scope
4.'showI2Cdevices' was not declared in this scope
5.'fatalError' was not declared in this scope
and 14 more errors like this.
The display shows nothing except the white blocks in one row or sometimes both rows ,but the backlight comes on. I tried adjusting the potentiometer but there is not text appearing.
Please copy-paste the full Serial output.
There is little point in paraphrasing it. Just copy it.
Ordinary readers will probably spot the problem(s) from the diagnostic output.
But Bill Perry (the hd44780 author) is often on the Forum. And can offer expert advice.
David.
Did you properly install the hd44780 library?
Go to Library Manager (in the IDE menus, Sketch, Include Libraries, Manage Libraries) and in the Topics dropdown choose Display and in the Filter your search box enter hd44780. Select and install the hd44780 library by Bill Perry.
Yes I properly installed the HD44780 library, and in the terminal I got this (LCD initalization failed: -3)
Hard to see the power connections to the LCD ....but they don' t look appropriately 5v and GRD !! 
That is not the output from the diagnostic sketch. Did you run the diagnostic sketch titled I2CexpDiag?
The error "LCD initalization failed: -3" may mean unsupported device. Are you certain you have a PCF8574T
How about a photo of the back side?
What were you using to build I2CexpDiag sketch when you got the "not declared in this scope" messages?
Was it something other than the IDE?
If it was the IDE which version?
--- bill
That initialization failure message is not from the I2CexpDiag sketch. It is from the Serial2LCD sketch.
Please run the I2CexpDiag sketch.
-- bill
Hi,
Welcome to the forum.
What sketch are you using to test the LCD.
Have you looked at the examples that come with the library, one should be a "Hello World" sketch.
If you have written your own sketch, please run the library example, then post your code.
To add code please click this link;
Thanks.. Tom... 
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