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Author Topic: Only gibberish on LCD-screen.  (Read 1518 times)
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Hi everyone.

I am a total newbie who just got my Arduino Uno. Trying to learn but right now I am stuck.

I bought a cheap LCD screen from a store in town, it is compatible with HD44780 but I cant get it to work anyway.
The pins seems to be located in a different place compared to all the guides I have seen on the net, also the pin-out numbering is 1-14 with 2 blank pins.

I took some pictures for you to look at.

This is the LCD screen, note the 1-14 pinout with 2 blank pins. Text says 1602B v2.2


This is how I have it set up. I think you can trace my connections in this picture. The thick wires are coming from the 10K potentiometer.


This is my 10K potentiometer.. Now, depending on how I turn the potentiometer the "symbols" or garbeled text on the LCD changes.


Depending on how I turn the potentiometer the display changes what is shown. Sometimes it is blank, sometimes the screen is filled with black boxes.






I think either my wiring is messed up or the potentiometer is behind this.
I tried running different code and when using "scrolling" text I can tell that the LCD is being updated by how the pixels change, but only these weird pixels show up, never text.

Please help me out, this is the 3rd day I have been trying to fix it.  smiley-confuse
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The picture showing the board has an error on it, I hooked the potentiometer wrong when taking the pictures. One of the pins should go to +5 and one to GND, but in my hurry to hook it up for the picture both of them went to GND. Sorry about that. smiley-razz

The gibberish is still the same when pot is connected to +5V, 3rd LCD pin and GND.


Excuse the screw-up.  smiley-cry
« Last Edit: April 14, 2013, 07:14:30 am by fastson » Logged

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Your display is upside down, the pins are at the lower left edge of the pc board.

Displays with the pins at the lower left typically have a non-standard pinout so you cannot use most of the drawings and photographs that you find on the web as a guide.  The pin numbers, however, are numbered the same as all of the other displays.

Pins 14 and 1 are identified and you should be able to figure out the sequence between those two numbers. The unnumbered pins on your display are for the backlight and most likely the end pin is the cathode (-) as evidenced byt the fact that your backlight seems to be lit.

The bottom line is that your display is wired exactly backwards.


Don
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Well dang it. smiley-sad-blue

I will re-wire it and replay back. Thanks.   smiley-kiss
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Well I reversed it, rightside up and changed the pins to the other way around. Still no go.
No more backlight (unless I connect the two pins which I tried and it lit up), but still no text. Only a few black boxes appears after playing around with the POT then they fade. 
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I don't understand why you have a link between Pin Numbered 1 and the end ( unmarked ) pin. It seems to me to be shorting out part of the pot.
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I don't understand why you have a link between Pin Numbered 1 and the end ( unmarked ) pin. It seems to me to be shorting out part of the pot.
If this LCD had been wired correctly he would be connecting pin 5 (RW) to pin 1 (GND) which is what should be done.

Don
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Well I reversed it, rightside up and changed the pins to the other way around. Still no go.
Can you provide a photograph of your current connections?

Don

Edit:  I think I gave you some bad advice about reversing the pins.  See the next post.
« Last Edit: April 14, 2013, 12:37:37 pm by floresta » Logged

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"The bottom line is that your display is wired exactly backwards."

Now that I think about it this wasn't exactly correct.  Your display was upside down and you had misinterpreted the pin numbering but you could have fixed things up by shifting your display to the left by two positions in the breadboard.  Sorry about that.

Don
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Ok, I will try again and post pictures of my results. Thanks for helping me out.  smiley-kiss

It would be so much easier (for newbies at least  smiley-kitty ) if the manufacturers labeled their pins.  smiley-neutral
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HEUREKA!  smiley-lol

Like you said floresta, move it two steps in the original configuration, and voila.  smiley-eek-blue


This is the messy setup. smiley-razz


FINALLY. Thanks for helping me out.  smiley Hopefully I can help someone in the future.

Now I hope someone with the same problems will find this thread via Google. smiley-razz
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