----- Original Message -----
From: Peter McNulty <petermcnulty@HOTMAIL.COM>
To: <PICLIST@MITVMA.MIT.EDU>
Sent: Thursday, December 05, 2002 2:17 AM
Subject: [EE]: LCD Initialization and Usage Sequence?


Hi,

....snip....
The datasheet doesn't give much information, so could someone run throught
he steps needed to get this working. According to the datasheet it should
go:

LCD Initialize:
Power on -> Wait 15ms -> Send Function set -> Wait 5ms -> Send Function
Set -> Wait 100micros  -> Send Function set -> Wait 50micros -> Send
Function Set -> wait 50micros  -> Send Display Off -> wait 50Micros -> Send
Clear Display -> Wait 2ms  -> Set Entry Mode -> wait 50 Micros -> Finish

But, it's it a bit weird that function set is being set 4 times, and I've
never seen this in the code before. I've never seen so many waits in the
code before either.

As for the writing to the LCD, it only gives a little image which doesn't
help at all. Also, it says send the E pulse or something. Is this simply, on
for 1 clock cycle, off for 1 clock cycle  on the E line? Also,  for the
write sequence, do i just send the data over DB0-7 or do i have to do
something else with RS and R/W. I know the E pulse has to be sent when
sending but that's it.
...snip....
Thanks
-Peter

Hi, the weird repetition maybe a result of the mode your controlling the LCD
with.  I know in 4-bit mode (usually uses DB4-7) you have to repeat codes to
send to the LCD.  Are you using 8bit (DB0:7)? 4bit? serial (doesn't sound
like it)?  The E line is used to 'clock' in your data on the data lines.  It
gives you time to setup what you want to send to the LCD on the data lines
then when your code toggles the E line the LCD grabs what is waiting at the
data lines.  I'm not sure how long the E pulse should last, a data sheet for
the HD44780 should say.  I use LCDs that have KS0066U controllers.  It says
to pulse for 450ns.  So a few 'nop's in your code should do the trick.

If your just worried about writting to the LCD and not reading, then you can
 ground the R/W line.  This simplifies things.  The RS line is used to tell
the LCD that the value you place on the data lines is either to be used as a
command or as data to display on the screen.  It should only go high when
you want to display data.  During the initilization it should be at 0.

Hope it helps.
Brendan

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