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Hello all,
This is my first post in this forum. I am a self-proclaimed character lcd graduate; I can make my own software(parallel and pic) for them and build them in less then 15 min. After seeing coorz's orange plenar lcd, I decided I should start on the graphics lcd scene. I have a few dumb questions, and I was hoping someone could answer them for me:
->The whole controllerless thing confuses me. How can you add a controller? Why wouldn't there be one in the first place?
This is my first post in this forum. I am a self-proclaimed character lcd graduate; I can make my own software(parallel and pic) for them and build them in less then 15 min. After seeing coorz's orange plenar lcd, I decided I should start on the graphics lcd scene. I have a few dumb questions, and I was hoping someone could answer them for me:
->The whole controllerless thing confuses me. How can you add a controller? Why wouldn't there be one in the first place?
Hiya Penjuin. Manufacturers usually don't put controllers on LCD's because they're not sure what's going to be driving them or they want to keep costs down. eg. If a manufacturer was putting out a 640x480x65,536 colour LCD then they don't know if a customer want's to drive it via an LCD Driver chip or by converting a VGA/Composite signal. The VGA/Composite way is similar in concept to driving an un-controlled (tm) LCD in that the screen is sent a 2 dimensional array's of pixel data which the LCD displays and will keep displayed for a certain (usually measure in ms or us) period of time. After that the whole display has to be refreshed again. Anyway, LCD's with higher-level controllers will do this for you and all you have to do is tell it what to draw or update some video RAM. The lower-level LCD's that don't have controllers you have to tell it again and again what to draw, in raw format (like 50 to 60 times a second). That's a pretty average job of explaining it but it's late here and I've had a few drinks. Sorry
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->Why is negative voltage needed for contrast? Why can't you just put a pot on GND?
Who knows? Well, some LCD's come with built in voltage inverters so that you can just supply it with +5V DC and they will do the rest. Most of them don't though which means you have to design your own Inverter/Multiplier to drive it. I think it's got to do with the way Liquid Crystals work but I'm sure someone else here can give you more details. It's a pain, I know, but you can find voltage Inverter/Multipler circuits all over the internet so it shouldn't be too much of a big deal
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->Where is a cheap place to get a small graphic lcd? (I want to start small and build up; not ebay)
Try one of:
* www.CrystalFontz.com
* www.matrixorbital.com
Also, try this link: http://www.allelectronics.com/cgi-bin/c ... type=store
It is a nice little LCD that is easier to program for than most graphic LCD's. You don't have to worry about multiple controller chips and the graphics memory is laid out in a fairly intuitive manner
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->Is a SED133x controller an ic that you go and buy, or is it something else?
Well.... you CAN buy them, but it's not always easy as they are usually sold in bulk to manufacturers. There are people/company's around that will sell these devices but almost all of them are surface mount. I wrote another thread about a 240x160x512 color LCD display that can be driven without an LCD controller if you're interested:
http://forum.lcdinfo.com/viewtopic.php?t=1383
Anyway, it's a VERY interesting project (at least to me) and will teach you a lot about how to drive LCD's that have no (or atleast, very dumb) controllers)
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Thanks in advance to anyone who can help me.
-penjuin
-penjuin
No problems
Anyway, I hope that helps a littleHumanBe**a**n (I forgot the 'a' when I signed up
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. All but one of my character lcds are from there, and i've also got some dirt cheap atmels. Let me know how the 128x64 turns out.