Troubleshooting LCD Screen

I am having trouble getting an LCD screen to work following the hello world sketch in this documentation:

https://docs.arduino.cc/learn/electronics/lcd-displays/

The top row of the screen fills with squares and then goes blank, and nothing prints. I have tried multiple screens. How can I further troubleshoot?


I see several problems, but without more documentation I can only guess. First your soldering is poor and needs to be fixed. Second I do not see the required contrast pot. I think there are more such as it does not illuminate. You did post some nice pictures, very clear.

The symptoms you describe indicate that the LCD has power, but communications are not functional.

That is most likely due to poor connections. The header pin soldering is poor, and an obvious suspect, so go over all those joints until they are properly filled. Adafruit has a good soldering tutorial.

Most are cold solder joints.

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Simply use an I2C adapter to save time when troubleshooting.

Unfortunately they are designed for the dual row header interface, rather than the single row interface the OP has.

EDIT: OOPs, never mind - I had it backwards. I have both types and should have looked at one.

This is a picture of the adapter I use or one similar.


The LCD pins should align and you can simply plug it into the LCD and solder it in place. They can be gotten for less then a dollar from some sources.