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Connecting LCD? NEWBIE

yacto

New member
I am interested in the 20x4 LCD how would I go about wiring it to the computer, either using the parallel port or serial port, is there any diagram i can follow to fire it.
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jheiner

New member
It's easy with the Serial LCD's... Just buy a serial cable and plug it from the back of the LCD to the back of the computer. Easy as that.
 

yacto

New member
Hello,
I know that i could just buy one and solve the problem,
but I am really intersted in building one, using my circuits and electronics knowledge from college.

Is there a circuit diagram that i could follow to buid it.
Thanks
 

CF Tech

Administrator
{this is a recycled post}
You can download the data sheet for the display from the product page. There is a thread here that gives a schematic. However, see the comment in this thread about backlights and potentiometers.

Here is a page about 44780 based LCD's in general.

I have a utility (lcdprint.exe) written by Mike Lynch that will send a text file to a display. That can be good for debugging your cable.

There is a pretty good tutorial on connecting a parallel LCD at http://mpford.dyndns.org. Then click on "LCD Display", and then " Step by Step how to build an LCD Display" (it is a framed site).

There is another nice article here that shows connection in a PC.
 

yacto

New member
I checked out the diagrams on those website, but they all talk about the sanyo or seiko display, but i am planning on getting a
CFAH2004A-YYB-JP from crystalfontz, so i can still use the same diagram. also where am i suppose to get the 5V vcc from, if the lcd is going to connected with a parallel port.

Thanks..
 

CF Tech

Administrator
The important thing is that the displays have an "HD44780" compatible controller. All of the displays in question do.

Part of using a parallel (HD44780) instead of a serial is figuring things like the 5v, backlight and contrast out.
 

yacto

New member
I still dont understand one thing, how does the LCD get 5v power, is it trasmitted through the parallel port or i have to connect it some other way. i am just a little confused on it.
Thanks
 

Uller

New member
The parallel support uses TTL level logic (i.e. 0V-5V), so you could technically power it off that. But I wouldn't suggest it - and here's why.

The reason why it's a bad idea is because there are no standards, regulations, or etc about the current sourcing/sinking capabilities for parallel ports - and since most printers and other units are using totem pole (aka tristate) outputs, a lot of vendors use an ASIC chip that can't handle much.

Beyond Logic, which has some of the best notes out there on PC ports, writes that they've seen ports that can source as little as 4mA. That's about a fifth of what's needed to power a low-intensity LED.

The best solution is to steal 5V from a molex connector (the white four-prong plugs off your powersupply used to power drives).
 
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