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Topic: arduino mega and lcd HD44780 (Read 2392 times) previous topic - next topic


Hello, I am new to the world of Arduino, I want to create a controller for my ramp led to my aquarium.
First I need your help to connect my arduino to my mega HD44780 4x20 LCD. I use this screen:http://cgi.ebay.fr/LCD-Display-HD44780-4x20-chr-20x4-BLUE-neg-Backlight-/160574392993?pt=Bauteile&hash=item2562facaa1
I can not connect properly and display text. For now I only have 2 lines (white square) and contrast that work


I can not connect properly and display text. For now I only have 2 lines (white square) and contrast that work

My guess is that these are lines 1 and 3 which would indicate that you have connected the power, contrast, and back light correctly but the LCD controller is not being initialized properly.  This could be the result of incorrect wiring or incorrect program code.

In order to help you we will have to see a photograph that clearly shows the connections between your Arduino and your LCD.  We will also have to see the sketch that you are actually using.  We do not need or want a link to the sketch that you are attempting to use.



thank you for your help.
I wired this way:

LCD  Arduino
1 -> gnd
2 -> +5 v
3 -> middle potentiometer
4 -> 36
5 -> 35
6 -> 37
7 -> not used
8 -> not used
9 -> not used
10 -> not used
11 -> 26 pin
12 -> 27 pin
13 -> 28 pin
14 -> 29 pin
15 -> Contrast +5 v
16 -> contrast Gnd

potar: +5v -- pin 3 lcd -- Gnd


That doesn't help without the photograph and sketch.  



Aug 02, 2011, 11:00 pm Last Edit: Aug 03, 2011, 08:45 am by razmo Reason: 1

here's a photo of the first part of the wiring, I did not put the cable DB4 a7.
On the left Gnd and +5 v V0 contrast yellow on the right Potar and Gnd and +5 v of the screen

I tried to follow the post ladyada but the result is the same


I wired this way:

Oh I don't think so or did you have wires made of ether? You wired the first 3 and last 2 pins and missed all those in the middle. BTW, your image links sucked.

Follow this tutorial:




You wired the first 3 and last 2 pins and missed all those in the middle.

Is there anything unclear of what I said?

Starting from lcd pin 4 and ending at lcd pin 14, you didn't wire them to anything so why should it work?

The tutorial you followed is clear enough but you didn't follow it the entire way. You need to go back to it and find at which step you slipped away from it and resume.

If you can't understand some of the steps, you should point it out here so you can get helped. Grinding your teeth is not very useful  ;)


Hello has all,

I return towards you because I do not still arrive has cabler the ecran. I followed the tuto of ladyada has the letter and I can simply regler the contrast.
For reminder I use an arduino mega and I cable DB4 in 26, DB5 in 27, DB6 in 28, DB7 in 29, RS in 36 and Enable in 37


What language is this in? What you posted is not understood.
Please use your native language and Google translate.
Did you or did you not connect lcd wires 4 to 14?


to try to be as explicit as possible your picture clearly shows the arduino sockets 26-29 are not connected and pins 4-6 and 10-14 on the LCD are not connected.

If you do connect wires between these, then your sketch will need to change the line
Code: [Select]
LiquidCrystal lcd(36,35,37, 26,27,28,29);

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