20x4 LCD shows alternating blank lines

Question

I just acquired a Arduino learning kit, which includes a 20x4 LCD display. I was going to test it, so I grabbed an example "hello world" program from the Arduino docs, connected the display appropriately, and then "Voila! ... Oh, it didn't work.".

The display lights up both its backlight and characters, however not in any desirable pattern. The first and third lines are full white (display is white-on-blue), while lines 2 and 4 are full blue. See picture:

The below schematic is exactly how I've connected the display, which should be correct.

^{simulate this circuit – Schematic created using CircuitLab}

I triple-checked all wiring for any shorts, adjusted the potentiometer to a good value and quadruple-checked the connections, and wasn't able to find any errors.

The dead-simple example program is following:

#include <LiquidCrystal.h>

// LiquidCrystal display with:
// rs on pin 12
// rw on pin 11
// enable on pin 10
// d4, d5, d6, d7 on pins 5, 4, 3, 2
LiquidCrystal lcd(12, 11, 10, 5, 4, 3, 2);


void setup() {
    // Print a message to the LCD.
    lcd.begin(20, 4);
    lcd.print("hello, world!");
}

void loop() {
}

Answer 1

Just putting the jumper wires in the plated holes, doesn't always give a good connection. Try applying some lateral force, to make sure all of them have proper contact. Wiring looks otherwise fine.

A more permanent solution would be to solder some male headers to the display, so you can properly seat it into the breadboard.

Answer 2

I had similar problem and I found that I had wrong contrast/brightness. Communication was working but just the characters were invisible. I spent much time, changed the LCD and in the last minute before went to rubish I got it.