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how to wire parallel displays


New member
are all of the displays on this page wired the same way? http://www.crystalfontz.com/products/index-std.html

I just read this article (http://www.themodfathers.jolt.co.uk/?page=&action=show&id=6154) on setting up a cheap LCD and it specifically uses the 16x2 LCDs which I think are the same ones on that page. I'm just wondering if it would be wired the same way for other sized LCDs. I got a 634 recently and love it but a parallel display would be a lot cheaper to set up for other computers :) Also, are those the HD44780 displays? And would they be supported with crystalcontrol (CC has an option for the HD44780's, I'm just not sure if those LCDs use that), or would I need to find some other software to control them?

thanks in advance
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CF Tech

Yes, the CFAH* series is HD44780 compatible.

We officially do not support connecting "parallel" displays to a PC.

If you still want to go ahead with it, your backlight must have a current limiting resistor in series with it:

With parallel displays, it only takes 3 wires connected correctly to get the display to show that top line of characters (or lines 0 and 2 for 4 line displays) ... Vcc, Vdd, and Vo (power, ground, and contrast pins). That does not mean the rest of the wires are correct.

Set pin 3 (Vo) at about 1v for starters.

Check your wiring by inspection first. Having the power wrong will smoke the display.

Use CFAH_WinTest to initialize the display and debug the wiring.

If that doesn't work, check your wiring again.

99.9% of parallel display 'failures' in the hobbyist/PC user market are wiring problems.

Good wiring guides for HD44780 compatible LCD's can be found:








You can also go to http://forums.bit-tech.net/showthread.php?threadid=5582 and search for "assuming alphanumeric" and you will find a short Q/A post on parallel displays.


New member
Ok, thanks a lot for the quick response. I noticed that in some of the pictures, not all of the displays have the same amount of connections as the one in the guide I read (themodfathers one, which has 16 pins to connect). The very small ones at the top of the page only appear to have 14 where the huge 40x4 at the bottom looks to have 18 or more. Some of the guides seem to better about covering that than others. And if all else fails, the parallel displays aren't that expensive so oh well :)