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I was programming my PIC microcontroller to the 16x2 LCD (Hitachi HD44780) to test out some codes, but when I tested my circuit again, my LCD started going haywire displaying some fuzzy or corrupted characters.

It eventually went to displaying white blocks on both the top and bottom rows on the right side of the LCD. LCD image

I was programming my circuit at 5 V all the time, but I don't know why the LCD doesn't work anymore. I tried adjusting the contrast voltage on the potentiometer, but nothing else works.

Anyway to fix this issue?

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    \$\begingroup\$ Simple things first: Did you try turning it off and on again? Did you check your data connections? Could you have introduced a bug causing your MCU to send the wrong signals to the LCD? \$\endgroup\$
    – user253751
    Apr 25, 2015 at 21:58
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    \$\begingroup\$ It looks like problem with code not physical damage of display. Check your coding ! i am guessing you were not properly commanded @Astro77589 \$\endgroup\$
    – Photon001
    Jul 19, 2016 at 7:30
  • \$\begingroup\$ Anyone know what that display actually is? I know it is an old post but I'm curious as I haven't seen one with two rows of 18 pins. Perhaps the rows are duplicated. I'd expect a 44780 display of that size to only have 14 pins or 16 including backlight. A higher pin count might indicate an alternative controller. \$\endgroup\$
    – Oliver Broad
    Oct 18, 2019 at 11:10

2 Answers 2

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I have one of those and when I apply 5v to it coming off from 3.3v all of the characters that are written there become white squares just like it happens with your LCD, the solution is to go with a small screwdriver to the backside of it and dial down the brightness until you can see the characters again, maybe try supply it with less voltage.

P.S. I know you said you tried turning the dial down but please check first that you're not outputting squares to the LCD by loading a simple "hello world" style program and going from there. Don't forget to turn everything off for a few seconds and then ON again, also, there's always the possibility that it's your MCU that isn't doing things right, if you have a second MCU that you know for a fact to be OK, use it to test the LCD. Don't forget to check your connections.

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I am a still new to the world of microelectronics however, from looking at your graphic example I noticed some possible issues with the header pic welds. Looks like you might benefit from a little more solder on most of the data connection pads. I can see from the picture that the top of several header pins are exposed.

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