44780 LCD queries

Hi everyone,
I am trying to use CCM1620CSL(a 44780-based LCD module) and that is
the first LCD i am trying my hands on.
I have interfaced the LCD to a PIC and till now, whatever program I
run, the result is 16 black boxes on the 2nd line of LCD (it's a 16x2
LCD). Can anyone suggest why is it happening? Isn't the LCD
auto-initialized in the 8-bit, 1-line mode when no initialization
routine is found ?

I've few more questions:
1) Can initialization be done only at the time of applying power to
the LCD? Suppose I wish to change the entry mode in the middle of my
program, how is it done?

2) Ideally, what do you expect to see on the LCD screen if ONLY power
is applied(i.e only Vdd,Vss & Vo are connected and rest of the pins are
left open)

Any help is welcome.
TIA
-Ankur

 

The initialization requirements for the 44780-style modules are strict.
What you describe is characteristic of what happens without proper
initialization.

You're correct in that the module wakes up in 8-bit mode. However, even
in 8-bit mode there are a few time-critical steps that need to occur to
wake it up properly.

A good reference is http://www.optrex.com/pdf/Dmcman_full.pdf. Note that
this is for a particular manufacturer and, while the values will work
with most 44780-compatible modules, there may be some with slightly
different timing requirements with "clones." Consult the specific data
sheet, if available.

Initialization is just that. However, there are commands to clear, to
change the operating mode, and to manipulate the display.

Datasheets are your friends.

One black bar. IIRC, the black bar is on line ONE and not line TWO. Any
chance that you have the display (and interface pin numbering) reversed?

 

Hello Webb,
Thank you for the elaborate suggestions. The data sheet I currently
have, is least informative and I couldn't find any other datasheet of
the same manufacturer on the web.

I will work more on getting the initialization right. Can you tellme
what is observed on the screen when it gets initialized
successfully?(incase it is not different for different modules)

And the black bar(16 consequtive boxes) are in the lower line(line
TWO, i guess). And I don't think that the display might be reversed
internally.Still, I'll find it out once i get through something.

Thanks & Regards
-Ankur

 

Initialization is just to a blank screen with or without a cursor (a
determined by the initialization).

One thing you'll need to decide on is whether you write to the display
with a fixed delay after each character (and a longer display after each
"clear screen") or whether you read back the "busy bit" from the display
controller.

 

This page tells you how to initlize the 44780.
Check out the links given on this page as well. My first success was a
result of reading this page. I would forget the data-sheets, except
for pin hookups, and timing requirements. Those things still confuse
me sometimes.


http://www.myke.com/lcd.htm