I have found on my 2 line LCD module that when it is initialised badly
(or wrongly) the top line is all black, and the bottom line is clear.
The blackness is varied by the LCD contrast, from light grey to black,
but only on the top line.

If you are using a 1 line display (I think this was stated in the
original message) then your one-line is equivalent to my top line, so
the entire display is black.  If a display is working you do not need to
get the potentiometer _just right_, you will get a readable display over
about 5 or 10 degrees of pot adjustment.

The problem is probably initialisation.  I was very frustrated with my
first attempts, and you get no diagnostic information out of the module
at all, so keep trying.  Luckily I have a Basic STAMP, and a program I
knew drove the LCD correctly, so I was able to verify that the module
worked, it was just my PIC code that didn't.

Perseverance pays,

Andy
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