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Topic: Hitachi HD44780 LCD Driver General Questions (Read 91 times) previous topic - next topic

gismo

Jun 10, 2015, 11:37 pm Last Edit: Jun 10, 2015, 11:38 pm by gismo
I'm skimming through the data sheet and can't find answers to the following about how the LCD will function. In particular, I have a 16x2 for example purposes, but I understand this chip applies to many different size LCDs.

  • When writing more than 16 characters on a row, is it possible to automatically overflow to the next line?
  • In any case, ff there is NO overflow to the next line, what's the maximum amount of characters that you can send to a line?(Then the display can be scrolled)
  • Is there any type of insert/overtype modes similar to a computer keyboard? Seems like there is only overtype mode


I found one thing in the data sheet:
" In a 2-line display, the cursor
moves to the second line when it passes the 40th digit of the first line."

but this is regarding the cursor position. I wil try to do some testing on my own for this as well.

If anyone has any answer, it's much appreciated. Thanks!

gismo

Well, I just did some testing, it seems like 40 is the max characters per line. If you go longer than 40, it will overflow to the next line. If you got longer than 80, it will make a full circle and start to overwrite the first line again....So max is 80 chars

floresta

(1) No

(2) That depends on the specific display.  As you have determined already the device can store 80 characters, but how that corresponds to the lines (actually rows) on the display depends upon the display itself.

(3) No

You must understand that these devices were not designed to function like a computer monitor.  The intended use was to display short messages such as "Add toner", "Paper tray empty", etc.


You can find a complete explanation by following the LCD Addressing link at web.alfredstate.edu/weimandn

Don

Paul__B

You must understand that these devices were not designed to function like a computer monitor.  The intended use was to display short messages such as "Add toner", "Paper tray empty", etc.
And honestly, it makes no sense to attempt to use them as a display for streaming information as it will simply not be legible.  They have quite significant lag (check out this demonstration and vary the "FPS" value "f" to assess it) and as they scroll character at a time, you cannot really perform a "Times Square" display comfortably.

The limited set of hardware primitives clearly precludes "insert" mode but again, there is no real use for it insofar as you are not going to use it with a keyboard to compose text (are you? :smiley-eek: ).  I realise some typewriters used to be available with one or two 80-character lines of text, but suggest you would have difficulty (and considerable expense) locating such displays nowadays.

Just conceptualise it in terms of what it is: two (or four) separate lines of text; you write to each as required by a setCursor() command and the characters you print overwrite whatever was there before.  You can of course, alter a specific "field" only but may need to add extra space characters to ensure - for example updating numeric values without leading zeros - that the whole of the previous message is erased.

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