HD44780 not displaying anything?

Hello Everyone,
I have Mount HD44780 with arduino, and have done all connections according to given diagram (although i have practice many other configrations to check if i am doing it right but nothing works), my HD44780 display turns ON (as shown in the picture) but when i burn simple example of Hello world my Liquidcrystal library it displays nothing. so i decided to connect V0 pin with 10k potentiometer to check maybe the contrast was the issue but by rotating the nob it shows oly half gird as shown in picture. i am unable to figure out the problem? is my HD44780 led is not working properly?

#include <LiquidCrystal.h>

//LiquidCrystal lcd(RS, E, D4, D5, D6, D7);
LiquidCrystal lcd(7, 8, 9, 10, 11, 12);      // put your pin numbers here

void setup()
  {
  lcd.begin(16, 2);                          // put your LCD parameters here
  lcd.print("hello, world!");
  lcd.setCursor(0,1)
  lcd.print("it works!");
  }

void loop()
  {
  }

these are the connection i followed:

What Arduino board.

Does the backlight work?

Post your code. Read the forum guidelines to see how to properly post code.
Use the IDE autoformat tool (ctrl-t or Tools, Auto format) before posting code in code tags.

Post photos of the wiring and the LCD.

Have you tried adjusting the contrast pot?
The correct way to wire the contrast pot is to wire one end of the pot to ground and the wiper to pin 3. The other end of the pot not connected. The long standing advice that the pot is wired to ground, Vcc and pin 3 is wrong. It is an error perpetuated over many years that begs correction.

Do you see a row of blocks on the top row of the LCD?

Also, unless you are certain the backlight LED has a built in current limiting resistor, add one on the LCD Anode pin.

What Arduino board.

i am using arduino promini.

Does the backlight work?

yes as you can see in attached picture.

Post photos of the wiring and the LCD.

Post your code.

i have run hello world program from liquidCrystal Example.

#include <LiquidCrystal.h>

//LiquidCrystal lcd(RS, E, D4, D5, D6, D7);
LiquidCrystal lcd(7, 8, 9, 10, 11, 12);      // put your pin numbers here

void setup()
  {
  lcd.begin(16, 2);                          // put your LCD parameters here
  lcd.print("hello, world!");
  lcd.setCursor(0,1)
  lcd.print("it works!");
  }

void loop()
  {
  }

Have you tried adjusting the contrast pot?

yes i have tried and it shows only half blocks and within seconds its just fads away. you can see in image.

The correct way to wire the contrast pot is to wire one end of the pot to ground and the wiper to pin 3. The other end of the pot not connected. The long standing advice that the pot is wired to ground, Vcc and pin 3 is wrong. It is an error perpetuated over many years that begs correction.

I have tried it but the results are same. i shows only blocks for some thime and then they disappear.

Do you see a row of blocks on the top row of the LCD?

yes only half row of blocks, meaning 8 blocks in 1st row and 8 blocks in second row and it fads away within seconds.

i have also tried this but nothing happens.

The pin numbers in the image of the wiring diagram are not readable.

Are the pins that you have connected the same as here:

//LiquidCrystal lcd(RS, E, D4, D5, D6, D7);
LiquidCrystal lcd(7, 8, 9, 10, 11, 12);

The schematic shows how it should be wired. Post a readable schematic.
Photos of the actual wiring show how it is wired. Post photos of the actual wiring and LCD.

The half display is characteristic of a hardware problem on a 16x2 lcd where the auxiliary controller on the back of the display is not communicating with the primary hd44780 controller.

See
https://forum.arduino.cc/t/16-x-2-display-only-shows-left-8-characters/152495/3

1 Like

What is the supply voltage for the Pro Mini? 3.3V or 5V?

I am not sure that I understand that. What else is connected to the Pro Mini?

Did you need to add a resistor to the backlight?

Very unlikely to be required indeed. Almost all of these "1602" displays have resistor "R8" as "101" or 100 Ohms.

Now note that the photo shows "blocks" in the right hand half of the display only, and on both rows. The contrast is clearly set correctly (irrespective of ow the potentiometer is wired :grin:)

This strongly suggests a faulty display as I do not know how it can be initialised in that manner. :roll_eyes:

I did not know that a photo had been added to the original post.

I agree that is probably a bad unit.

Benefit of coming in late. :+1:

No photo (or no code), no idea what the problem is. :roll_eyes:

Your image of the connections are completly different than what are assigned in the sketch as noted by @ groundFungus in post #7.