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Topic: 16x2 LCD shows only black boxes in the bottom line (Read 30299 times) previous topic - next topic


nothing happened when i turned it over before...it was still the same.


Oct 14, 2012, 03:55 pm Last Edit: Oct 14, 2012, 03:58 pm by floresta Reason: 1
nothing happened when i turned it over before...it was still the same.

No it was not the same, unless you have a very unusual display.



i know this topic is closed but many of will coming here with the same problem
i was facing this problem too and just find out why it was.
one thing is very clear that you are watching lcd up side down
as i was doing too. and second thing that led is not being communicated.
in my case i didn't conected the r/w to ground by connecting its working properly


in my case i didn't conected the r/w to ground by connecting its working properly

You obviously have looked at some old threads but you haven't gone back far enough.  The problem of not connecting the R/W line was quite prevalent several years ago but has only shown up one or twice in the past few years.  The connection is clearly shown in the diagram with the tutorial (http://arduino.cc/en/Tutorial/LiquidCrystal) and is also mentioned in the program comments.



hello, i know the topic is old but i have a strange problem.
I conect my LCD like this
And when I conect my USB cable and upload sketch the LCD works, but when I unplug the USB then plug it again it just show the first black row. When I upload sketch it work again

  LiquidCrystal Library - display() and noDisplay()

 Demonstrates the use a 16x2 LCD display.  The LiquidCrystal
 library works with all LCD displays that are compatible with the
 Hitachi HD44780 driver. There are many of them out there, and you
 can usually tell them by the 16-pin interface.

 This sketch prints "Hello World!" to the LCD and uses the
 display() and noDisplay() functions to turn on and off
 the display.

 The circuit:
 * LCD RS pin to digital pin 12
 * LCD Enable pin to digital pin 11
 * LCD D4 pin to digital pin 5
 * LCD D5 pin to digital pin 4
 * LCD D6 pin to digital pin 3
 * LCD D7 pin to digital pin 2
 * LCD R/W pin to ground
 * 10K resistor:
 * ends to +5V and ground
 * wiper to LCD VO pin (pin 3)

 Library originally added 18 Apr 2008
 by David A. Mellis
 library modified 5 Jul 2009
 by Limor Fried (http://www.ladyada.net)
 example added 9 Jul 2009
 by Tom Igoe
 modified 22 Nov 2010
 by Tom Igoe

 This example code is in the public domain.



// include the library code:
#include <LiquidCrystal.h>

// initialize the library with the numbers of the interface pins
LiquidCrystal lcd(11, 12, 7, 6, 5, 4);

void setup() {

  // set up the LCD's number of columns and rows:
  lcd.begin(16, 2);
    // Turn off the display:
  lcd.print("CRM 180");
  // Print a message to the LCD.

void loop() {
    // Print a message to the LCD.


I use arduino nano clone 328


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.



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).

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