16x2 LCD shows only black boxes in the bottom line

hello, i know the topic is old but i have a strange problem.

Then start a new thread.

Post a photograph of how you actually connected your components rather than a link to a site that shows how you are supposed to connect things.

Check your link to verify that it works, yours doesn't.

Use the 'code' button to correctly display your code. Read the forum instructions if you don't know how to do this.


On extrenal power it is working OK, so is somethnig about when computer is looking for arduino hardver, never mind it will work on extrenal power, problem solved :)

Found this thread because of a similar problem. The last reply gave me the answer. I reasoned that if an external supply worked and the USB->Arduino cable didn't, then it might be because the battery voltage was lower and more appropriate. Sure enough, it turned out that I have a 3.3V display (not marked on the board, however), and I had been powering it off the Arduino's 5V supply. Doh!

I hope this helps someone else.

I realize this is an old topic, but I found it because I was having a similar issue. In my case, it turns out that the eBook example had a pair of switched connections to the LCD. Knowing how the LiquidCrystal() command is configured allowed me to troubleshoot the problem.

For beginners, be sure to use Include Library in Arduino app for LiquidCrystal.

Resources: https://www.arduino.cc/en/Reference/LiquidCrystal https://www.arduino.cc/en/Reference/LiquidCrystalConstructor

OK, if we are looking at old topics, a little memo:
Do not connect the contrast potentiometer to Vcc.

If you have a board on which it is connected to Vcc, it will be beneficial (make contrast setting easier and reduce current consumption by 450 µA) to cut that connection (as long as of course, you do not cut any other connection to Vcc in doing so).

I too have problem regarding this Why is it showing error

robodig: I too have problem regarding this Why is it showing error

How would we know?