>> control the contrast that uses negative voltages.
 >> Is that really necessary?

Yes, if you have an "extended temp range" LCD module.
No, if you have a "standard temp range" LCD module.

 >> Wouldn't a voltage 0-5V be all that is needed for that?

In the "No" case above, yes... :-)

 >
 > For a common 16 x 2 yes.
 > The best contrast is often when Vo is just above 0V
 >
 > wbr
 >

And in that case "common" equals "standard temp range",
which normaly actulay is the case... :-)




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