New LCD display not working, only show light and boxes

Other Hardware General Electronics
1

dear everyone.

i bought a bunch of LCDs with I2C from china and i used some of them and they work great. after a month of the purchase, i opened one of the NEW LCD displays and only exchanged the wires with a perfectly working one (to make sure there is no code or wire errors) but its not working.

when i switch back to the old one it works, so the NEW one definitely have a problem.

is there a different library for the same model LCDs?

** i adjusted the contrast and no luck, only light with first row of boxes showing.

2

The new I2C LCD display probably has a different address than the old LCD.

Run the I2C scanner to discover the addresses of all the displays and write those addresses on the back of the LCD PCB for future reference.

3

checked the address and its the same, and that why i knew it is kind of working

4

I always use this library:

hd44780.h

Read the Library Overview

1 Like
5

Having the same address is not a guarantee that the same code will work.

Please post a link to the displays you have. Are these 16x2 or 20x4 character LCD displays with an i²c backpack soldered to the back of the display?

Does the design of the backpack look identical on the working and non-working displays? If you can see differences, the same chip may have been used (hence the same address) but the wiring between that chip and the display could be different.

6

One of the advantages of using the hd44780 library is that it will automatically detect the I2C address and the pin mapping between the LCD and the I2C backpack making the display nearly plug and play.

Included in the examples for the hd44780_I2Cexp class is a diagnostic sketch whose output can help to troubleshoot a display that is not working right.

7

All are 16×2 and its lcd with i2c on the back already soldered.

Its identical as far as i know.

I Will double check it

8

I will try it and update the post

9

Have you fitted the pot to adjust the contrast ?

10

Yes, this is quite a basic procedure.

All normal procedures i tried.

I thought its defective but thr problem is that it read and detects the i2c address so its fine

11

That means that the i²c backpack it working, but the LCD itself could be faulty.

12

Ohh, i will upload a picture because the screen has tiny dent but it maybe the problem.

13

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