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Topic: 16x2 LCD Troubleshooting (Read 2608 times) previous topic - next topic


I spent a while looking through the forums for a solution to the issue I'm having with connecting a 16x2 LCD, but haven't come across anything quite like what I'm seeing. I followed this tutorial for wiring the connections: http://www.ladyada.net/learn/lcd/charlcd.html

I also made the necessary code changes to the LiquidCrystal HelloWorld sketch mentioned toward the end of the tutorial, namely the note about changing this:
Code: [Select]
LiquidCrystal lcd(12, 11, 5, 4, 3, 2);

to this:
Code: [Select]
LiquidCrystal lcd(7, 8, 9, 10, 11, 12);

Unfortunately, when I load and run the sketch this is what I see on the LCD:

As far as I can tell, everything is connected correctly. I even double-checked the header pin soldering for connectivity and shorts. The pattern shown on the LCD is at maximum contrast. This pattern was persistent before I connected the data lines (only backlight, pot, logic power connected) and goes away when the pot is turned down. I never got a single line of blocks mentioned in the tutorial at that step. I was thinking that there was something wrong with the LCD, but I tried a 2nd LCD to the same effect.

It would help if a 2nd (or 3rd, or n) set of eyes could look at this and give me some feedback. Thanks!

Nick Gammon

What's the exact part number of the LCD?
Please post technical questions on the forum, not by personal message. Thanks!

More info:

Nick Gammon

Looks OK to me. Try measuring that you have +5V on the pins that should have it.
Please post technical questions on the forum, not by personal message. Thanks!

More info:


The wiring and "code" look good to me too. Could be a bad display. Someone asked about this pattern in the past and if I recall correctly he/she sent it back for a replacement. Where was this display purchased?


I got the display a few years ago from sparkfun.com. I figured it might be the display malfunctioning, so I ordered a 2nd one, different color, same model... similar result. I read that these LCDs are pretty robust, so I'm not so sure it's the display.


I've purchased from several sources (not including sparkfun) and never had any problems of defective screens, even from surplus stores. I think the other guy with similar problem also bought from sparkfun. Maybe sparkfun got a bad batch.


Just out of curiosity, what does the display look like without connecting the six red wires to the Arduino ?  Normally you would get 'boxes' on the top row.



Try the tutorial from Hacktronics.  It worked for me.
Make sure you have the LiquidCrystal.h library loaded
on your computer when you compile the sketch.




Thanks for everyone's replies! I meant to get back about this earlier. I ordered a new LCD from sparkfun and when I wired it up, everything worked as expected. What are the odds of 2 bad LCDs in a row?

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