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Author Topic: Half of LCD Blank, other half full.  (Read 814 times)
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I am trying to use the HelloWorld sketch on my arduino UNO, and this is what happens:



My connections are these: 
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Western New York, USA
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If you look on the back of your LCD board you will find two ICs (or two epoxy blobs).  One is the main controller which contains all of the brains, all of the memory, and the circuitry to display16 of the characters.  The other is an auxiliary controller which is used solely to display the other 16 characters.  I don't think there is anything that you can do with your connections or with your sketch to come up with the display that you have.  It looks like your main controller is defective.

Don
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I think it is the connections, because if i apply pressure, it will work, but one side has more contrast than the other and it sometimes makes the text a little garbled.
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When I spoke of 'connections' I meant the wires between the LCD module and the Arduino.  The connections you are referring to are those between the LCD display and it's PC board and they very likely to be the problem.  In any case the solution is the same, and it doesn't involve wiring or programming.

Don
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Hah, I figured out the problem, there were very tiny bridges on the 4 bit pins and it was making the screen go wonky, I removed the bridges, and then it worked!  smiley
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there were very tiny bridges on the 4 bit pins
Are you talking about some combination of DB4, DB5, DB6, and DB7?  If so I'd really like to know which pins were bridged.  I didn't think you could disable half the display without attacking the PC board itself.

Don
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But maybe it really isn't disabled but just displaying <space> in the "blank" areas
vs a full pixel character in the other locations?

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But maybe it really isn't disabled but just displaying <space> in the "blank" areas
vs a full pixel character in the other locations?
It looks like more than a 'full pixel character' since a bunch of cursors are showing up as well, and I don't think that happens normally.

Don
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I've seen weird stuff like that when the display is sent garbage and it somehow goes
into 5x10 mode.
I also saw something that I was unable to reproduce that caused pixels to be much brighter
than normal on a display like that.

Normally I don't send trash to the display, it was during the debugging of a
shift register circuit I was designing where my hardware was not quite stable yet.
The circuit uses a single wire (arduino pin) and a shift register to control everything including
the backlight.

--- bill
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