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Brussels
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Hey guys!!
I'm a good noob so it should be easy to answer me smiley-wink

I bought the Due a few days ago since i used up all my Uno's capabilities. I'm now trying to transfer my project onto it, but i'm having trouble figuring out how to connect the 16x2 lcd screen. (It's the one you get in the Arduino starter kit.)
So here are my questions:
1) On the Uno the screen uses 5V, so what's going to happen with the Due's 3.3V? the power, the led backlight... what goes to 5V what doesn't?
2) Is the library compatible? Does my code have to change?

cant find any info on the web...

Thanks a lot!
E
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Due board has several 5 volts sources and grounds. 

I am using a Matrix Orbital 4x20 lcd, I connected the supply wire to 5 volt on Due, ground wire to ground on Due, that is how I power it up.
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Brasil
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LCD 16x2 only requires OUTPUT data pins from the DUE. This means that: connecting 3.3v to a 5v microcontroller (that is the LCD), will not cause any harm. Since the logic HIGH and LOW values are commonly setted as higher than 2.5 or above, 3.3 is just fine to work with the LCD.

However, you will need to supply 5v to the LCD and also the backlight, or, it might not work...
So:
Data Output pins from due can be connected without any external hardware.
Data Output pins from LCD, NEED some sort of "level-shifting", but you don't need Input pins from LCD
Power supply: 5v to the lcd (3.3 might not work)
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Brussels
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One tiny more thing: the usual LEDs i use need a 220ohm resistor in series when powered by the Uno. Do i still need the resistor using the Due?

Thank you!! smiley
E.
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Brasil
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Resistors are not to lower thw voltage, in this case is to pimit the current.
I would use the resistor...
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Brussels
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Ok, thanks.
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