Arduino LCD only showing black boxes on bottom row

Question

Disclaimer: This is homework.

I'm taking an Arduino class and for our project we have to implement a simple sketch. The hardware involved is the Arduino Mega ADK board and the Electronic Brick Starter Kit. I have been able to successfully communicate with the Arduino with my sketches; other things (like the push-button, and LED's) seem to work, except for the LCD. I've followed numerous tutorials (including the on sample program for LCD's in my second link), but I can't get anything to work. My LCD consistently shows black boxes in the bottom line. From looking around, I see that black boxes show up when the LCD isn't connected properly. However, this is a starter kit which contains cables that you can hook up to a chassis, which gets rid of the pain involved in soldering individual wires. Is there something wrong with my LCD? Here's a simple sketch that I'm unable to get to work:

#include <LiquidCrystal.h>

LiquidCrystal lcd(10,11,12,13,14,15,16);

void setup()
{
  Serial.begin( 9600 );
  lcd.begin(16, 2);
  lcd.clear();
}

void loop()
{
  lcd.setCursor(0,0);
  lcd.println( "hello world!    ");
  delay(1000);
}

The pins correspond to BUS2 and I've properly hooked up my cable from BUS2 to the LCD.

Solution 1

My LCD consistently shows black boxes in the bottom line.

I had similar problem. Was connecting the LCD using minimum number of pins: LiquidCrystal(rs, enable, d4, d5, d6, d7). The problem I had is that I didn't connect R/W (Read/Write) pin of the lcd to GND. When I did this - it has started to work. Also I found useful to add a 3.3k resistor from Vo (Contrast Adj) to GND so the text can be read easily.

Solution 2

Please ensure that you have all your header pins soldered ok in the LCD.

If you are using header pins without soldering in the 16 holes of you LCD move your LCD until you find a stable position for testing. Its easy that not all of them are contacting

This basic helloworld example should work http://www.arduino.cc/en/Tutorial/LiquidCrystal

For testing push load in the arduino IDE for uploading the script. Reset button in the arduino board sometimes is no initializing the LCD

Solution 3

You should check your LiquidCrystal lcd(). Got the same problem and i adjusted this and now it works.

Comments

[A.H.]

He writes, that the black boxes are in the bottom line. The output of the string should be in the top line. So I doubt that this correlates.

[Vivin Paliath]

My teacher seems to be having the exact problem, but on the top row. Neither of us have been able to find a solution as yet. He mentioned that other students have been trying to resets and turning off the LCD to clear its state, with varying degrees of success (didn't work for me). I also think that it might be an issue of initialization, but the API doesn't seem to provide very much other than lcd.begin() for initialization. I will try the delay(1000) once I get home.

[SCO]

Except if his LCD was upside down ;)

[yves]

encountered the same : it was a soldering issue, even if it look goods, it is not so easy to solder properly this small pins.

[sud007]

tried both, connecting to 10K Potentiometer and another one via DigitalPin 6, none worked, same issue. Same blocks.

[sud007]

2022 and this is still the problem with mine. Got 2 more LCDs, same issue. My Electronics partner is way more helpful with replacing those LCDs, then the documentation; meh!