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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

Reply to
ankur
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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

Reply to
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

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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?

--
Rich Webb   Norfolk, VA
Reply to
Rich Webb

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.

--
Rich Webb   Norfolk, VA
Reply to
Rich Webb

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.

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Reply to
jon.stephenson

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