View Full Version : Can Parallax serial lcd be converted to parallel?

12-22-2011, 03:30 PM
I have a serial lcd which only displays the test screen. I replaced it but I never threw it away. I wanted to know if I could desolder the serial controller board and replace it with a ribbon cable? It may not be worth it because I would have to order a new ribbon connector.

12-22-2011, 03:33 PM
Perhaps you could use this http://www.sparkfun.com/products/258

12-22-2011, 03:35 PM
Sounds possible, especially if the LCD was a HD44780 compatible one. You could probably even wire it in four bit mode to save I/O pins. Sounds like a lot of work though. I always have a few parallel LCD's laying around just in case something like that does happen. What model is it?

12-22-2011, 04:01 PM
OBC is giving away free LCDs at http://forums.parallax.com/showthread.php?136351-2011-Holiday-Givaway&p=1061068&viewfull=1#post1061068

Free with free shipping? How can you beat that?

Loopy Byteloose
12-22-2011, 04:59 PM
It does seem a rather odd question as the usual parallel LCD is cheaper than the serial LCD.

The parallel LCD takes either 7 pins of a microprocessor in 4 bit mode or 11 in 8 bit mode (think 7-11), while RS232 serial can require as few as 1 and SPI might use only 2.

If you want, someone is likely to trade you straight across for a serial LCD.

12-22-2011, 06:01 PM
Franklin, that's a good link, thanks.
Ravenkallen, I bought it from Parallax so I guess it's compatable.
Erco, My first thought was "Christmas came early." But I realized I've already got a parallel lcd which I never learned to use because it needs 14 pins. (I'm trying to figure it out now.)
Loopy Byteloose, I'm motivated more by the educational value than the cost. Scavenging trashed lcds could be a good thing. :smile:

My current project will use 2 steppers, a keypad, an lcd and a servo. I'd like to learn how to connect my lcd as a 4-bit device so I could save some pins.

12-22-2011, 06:05 PM
I "converted" one after damaging the control board and wired it up on a bread board. Here's the thread.



12-22-2011, 06:20 PM
doggiedoc, so it is possible. That's the same one I have.

Loopy Byteloose
12-23-2011, 04:30 AM
4 bit mode is 7 I/O pin plus 3 power pins ( plus, ground, and contrast). That is a total of 10 of the 14. The 4 unused pins need to be tied to ground.

Getting the polarity right is imperative or you immediately destroy the LCD.