There are a couple common gotchas with these LCDs.

First: Double check that you are giving it all the setup and hold times
between the data and all the control signals.

Second: Double check that your delays are what you think they are.

Third: Make sure that your contrast voltage is roughly right, the display
pixels should  be just a little dark.  Without contrast voltage, or with the
wrong contrast voltage, you may have everything working, and STILL not be
able to see it!
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