Go Down

Topic: 4x20 LCD showing 2 dark lines (Read 226 times) previous topic - next topic


Dec 13, 2017, 05:29 pm Last Edit: Dec 13, 2017, 08:32 pm by adWhy
I'm using arduino nano, and i just bought RC2004A 4X20 LCD.I connected it to my arduino nano but it doesn't show me a text, but it is always showing two lines. 1line: clear     2line: dark     3line: clear    4line:dark. I tryed to search my problem, but i didn't find it. Wiring i used is the same as HelloWorld example, and code is the same too, i only changed from 16, 2 to 20, 4. By the way, my arduino nano is fake, if this makes any difference


Are these lines simultaneously or intermittently? Can you please supply a picture?


... but it is always showing two lines. 1line: clear     2line: dark     3line: clear    4line:dark ...
Your display is upside down but that is only part of your problem.

The display of those blocks means that you have the power connected properly but there is probably something wrong with one or more of the other seven connections.  Since the display is upside down perhaps you also have the wiring exactly wrong (reversed left to right).

A photograph of your setup would help.



Is the LCD Panel screwed on a board? If so, loosen the screws.


Dec 14, 2017, 02:17 pm Last Edit: Dec 14, 2017, 02:58 pm by adWhy
No lcd is not screwed on the board. I think everything with my wiring is okay, i chacked again, maybe im just holding lcd upside down. I will upload photos after few hours, i dont have camera now, since i lost my phone :D. By the way i didn't mentioned that i tryed to connect my 2x16 lcd in the same way and its worked, but on 4x20 its not working like I said, also i tryed to use i2c but i2c scanner doesn't even find my i2c, I connected i2c signal wires to a4 and a5 ports on my Arduino nano (fake). I think there is a problem with librarys or drivers, but you know better ;)


You didn't mention I2C before.  How could you be using wiring that "is the same as HelloWorld example" and also be using I2C?

If the scanner doesn't find your device then your sketch won't be able to find it either.

Are you using the same I2C adapter for both LCDs?  Probably not, so are they identical?  If they look identical check to see if the IC chips have the same part number.

The photos will help a lot.

Which library are you using?  If you aren't using 'hd44780' then you really should consider switching.



Dec 14, 2017, 03:28 pm Last Edit: Dec 14, 2017, 03:49 pm by adWhy
I used different example for i2c, and i also tryed without i2c. Wiring wasn't the same for i2c as for without i2c. My 2x16 lcd has number on its back: GDM1602A, and this lcd worked just fine, but my 4x20 like I said is showing two dark lines, read about that display and what i found is that it uses not hd44780 driver but its copy: ST7066. I'm new to this so lets concentrate on that two lines problem without i2c. I bought it because i thought that i need it to run my display :D. I didn't used i2c for 2x16 lcd, photos will be in few hours


Dec 14, 2017, 06:34 pm Last Edit: Dec 14, 2017, 06:45 pm by adWhy
Sorry everyone, i trusted my soldering power to much, when i were going to take a picture of my lcd for you, i saw that i actually solder everything upside down like you said, but i have another one problem, as i mentioned i would like to run everything with i2c, because you only use 2 ports. My i2c chip is called pcf8574at, i connected it to a4 and a5 pins on my fake arduino nano, but scanner doesn't find it

Go Up