Posted on December 19, 2012 at 17:06Connecting any/all of your lcd data bus to power or ground - prior to proper lcd initialization -accomplishes nothing! (in fact most all 44780/clone controllers ''pull'' the D-Bus high by default)
Here is the simplest code which can bring your first (top) line of character lcd into view:
Set RS=0
Set R/W =0
Set E =0
Place 0x0E on data bus (2 steps in 4 bit mode - 1st 0X00 then pulse ''E'' H-L. Then 0x0E on data bus - again pulse ''E'' H-L. If done correctly - the pixel field should come more intensely into view.
Once the pixel field is clearly viewable - place 0X01 on data bus. (again 2 steps - as above - first 0X00 then 0x01.) This 0X01 will clear the display and ''home'' the cursor.
As the other poster suggests - long delays during this process will be helpful.
If you can achieve this very basic ''make pixels visible'' and ''home cursor'' functionality you can graduate to fuller initialization (2 line) but ordering the display into 2 line mode may well require a slight negative voltage on Vo - as stated earlier...
*** Update ***
My suggested use of the minimum 2 commands (0x0E followed by 0x01) is correct for an 8-bit bus implementation - but is inadequate (wrong) for 4 bit operation!
To begin - tie 4 consecutive bits from your MCU to DB4-DB7 of the Lcd. (DB3-DB0 may float) Ideally (to simplify) you should use Port bits 4-7 from your MCU.
Now 4 bit initialization is specialized - and must be followed exactly: (this from a 1994 Hitachi LCD Controller Data Book)
Wait for 15mS (minimum) after Lcd's power rises to 5V.
a) Clear RS and R/W and E.
b) Place 0x03 on Lcd pins DB4-DB7. (i.e. DB4 & DB5 high, others low)
c) drive E high for 450nS minimum - return low.
d) Wait for 4.1mS (minimum)
e) Place 0x03 on Lcd pins DB4-DB7. (same as earlier)
f) drive E high for 450nS minimum - return low.
g) Wait for 100uS (minimum)
h) Place 0x03 on Lcd pins DB4-DB7. (this is the 3rd time this is done)
i) drive E high for 450nS minimum - return low.
j) Place 0x02 on Lcd pins DB4-DB7. (i.e. DB5 alone, high)
k) drive E high for 450nS minimum - return low.
l) Place 0x02 on Lcd pins DB4-DB7.
m) drive E high for 450nS minimum - return low.
n) Place either 0x00 (1 Line) or 0x08 (2 Lines) on Lcd pins DB4-DB7
o) drive E high for 450nS minimum - return low.
p) Place 0x00 on DB4-DB7 - strobe E
q) Place 0x01 on DB4-DB7 - strobe E (these 2 commands clear the Lcd)
r) Place 0x00 on DB4-DB7 - strobe E
s) Place 0x0E on DB4-DB7 - strobe E (display should now be visible
*** Now change RS from low to high, leave R/W low
t) Place 0x40 on DB4-DB7 - strobe E
u) Place 0x01 on DB4-DB7 - strobe E (A should now appear @ home position!)
Continue to write to the display via this back to back (2 nibble) mode - with most significant nibble sent first. Each nibble must be ''strobed in'' via a high going E pulse.
8 bit mode is far more forgiving - but does cost 4 more GPIO. If you use 4 bit mode in a noisy environment - it is wise to periodically ''re-initialize'' the Lcd - to make certain it has not become ''out of sync'' with your tranfers.
