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Everything Else » LCD questions

June 29, 2012
by sask55
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I am attempting to make a compact neat layout on a PC board for a project. I would like to find a LCD display that is very similar to the one in the NerdKits package. That is a 4 line twenty character LCD that is compatible with the Nerdkit display protocol. The only thing is I would like it to have all the connector pins located on the bottom of the display not the top. Sort of the same LCD only upside down, so the top line would be the bottom, left would be the right and so on.

From this idea, I have a few questions about the LCD communication protocol. I am sure this is basic stuff, so if someone could just point me in the right direction with a link to some information about what information is being sent to the LCD.

I do not know where the coding for the individual pixel output of the display is done? I assume it coded as firmware on the display and is therefore not changeable, is that correct? Is it possible to make new characters in software by setting the display state of individual pixels on the LCD screen? If this was possible to do, I am certain there would be all kinds of code around producing crude graphics on these displays. I don’t see any thing like that so I imagine the answer is that it can’t be done.

Darryl

June 29, 2012
by pcbolt
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Darryl -

Actually you can create custom characters with the HD44780 LCD module. Problem is you are limited to only 8 (new) characters. There is a NK library entry under the "How To" section near the bottom that shows how to do this. The HD44780 guide that is in the download section has some chapters on writing to the character generator RAM (CGRAM). I've used custom characters and it works fine, however I've never tried to create a custom character, display it then try to overwrite the custom character pattern to see if the previously displayed character changes. If you could do that you could in theory create a character set 8 characters at a time and revise them as needed.

June 30, 2012
by Rick_S
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I think (not nearly 100% sure though) if you overwrite a character you created with a new one, any character from that memory location that is currently on the display changes to the new character. I know one of the many display's I've played with does this, just not 100% if it is the HD44780 or not.

As for where you can buy display's compatable with NK code... Just about anywhere. Just make sure they state that they have an HD44780 or equivalent chipset. (Which most text displays do have). I've bought several on ebay, pillaged several from old printers and scanners, and bought some retail. They are VERY common.

Rick

June 30, 2012
by sask55
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Thanks pcbolt and Rick

I do not even have any electronic or Nerdkit stuff set up right now, it is kind of my off season. I will be reading up on this a bit. Just from what I hear so far developing an entire set of display codes that would produce text on the screen only upside down or possibly standing on end with 4 columns and 20 rows would be very difficult if possible at all. IT seams to me that it is likely the case that the images currently displayed on the screen will change if the custom character that generated that image is overwritten. That 8 new character limitation would likely be very troublesome even in the event that the screen does not immediately change what is displayed when a custom character is overwritten.

Developing the coding to accomplish what I was thinking about would be a substantial undertaking at best. The pixel display matrix for each individual character would have to be built. Moving left become moving right, row one becomes row 4, just to name a few think.

Come fall I will set up and do a little experimenting just to satisfy my curiosity about custom characters .

Darryl

June 30, 2012
by Ralphxyz
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Darryl, possible you will not want to use a HD44780 chipset.

How about just going graphical?

Ralph

June 30, 2012
by sask55
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maybe graphical, I will be looking into options for the next little while, I am not in a hurry.

Darryl

July 01, 2012
by Rick_S
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I was just going to suggest graphical too, but I see Ralph already did. Wink

You can get them in many different shapes and sizes and there is plenty of code out there on the web to generate text if that is what you want to display.

Rick

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