newbie question HD44780 or equivalent

johnmacd · Post by **johnmacd** » March 6th, 2006, 3:16 am

Sorry for the real newbie question. But I think I have a simple question. I think if I want to do this project, all I need is is a HD44780 or equivalent
LCD??? Well, not all I need, but that's the main component.

I would like to spend a small amount of money on this in the beginning, and then maybe later get a better LCD. Based on another user's post I ran into this ebay auction: http://cgi.ebay.com/HD44780-New-20x4-LC ... dZViewItem
Is this good enough?

I was thinking about getting a project box from RadioShack to mount this in and have it as an external LCD screen. Am I on the right track?

Sorry for the newbie question.

jonny · Post by **jonny** » March 6th, 2006, 4:18 am

I have two of that exact same lcd, bought from the same supplier, so yes, you are on the right track.

My suggestion is to focus on the wiring, not neccesarily on what it will look like. If you can figure out the connections, and get the lcd working, you have done 90% of the work.

_X7JAY7X_ · Post by **_X7JAY7X_** » March 6th, 2006, 4:32 am

That seller has been very good to me. Make sure you do not mix up the power wires, it will wreck the lcd. There are several schematics on here for parallel port use, or you can do a serial lcd using a microcontroller.

J

johnmacd · Post by **johnmacd** » March 6th, 2006, 3:17 pm

Thank yoou both for the quick answers.
Is there any advantage over using serial over parallel? I'll look around to find out what microcontroller is used for serial.

_X7JAY7X_ · Post by **_X7JAY7X_** » March 7th, 2006, 12:22 am

Check out more in this forum. There is a PIC version and ATMEL version.

Advantages? For one I would say reliability. You will find that some people have been using parallel for years with no problems. I personally have lost a few LCDs just to normal use on a parallel port. This is the reason that crystal fontz does not encourage it. Two, most computers usually have 2 com ports where as only one parallel port. Three, most serial LCDs have buttons and GPO ports and control both backlight and Contrast. I have not seen a schematic for both for parallel (I could be wrong).

J

johnmacd · Post by **johnmacd** » March 7th, 2006, 12:46 am

Thanks again for the quick reply. I'm gonna try the parallel just to get it running, then I will try the serial.

ReverseEngineered · Post by **ReverseEngineered** » March 7th, 2006, 2:04 am

Yes, the parallel port is definitely limited in its abilities. It was made for printers, and since then many other things have been used on them. While most are current-limited (to prevent destroying things), not all are. Also, many computers tend to send a large voltage to all of the pins on the port when they first turn on (they shouldn't, but they do). This can immediately fry anything that is hooked up to what it considers to be an "input" pin.

The advantage to parallel is that you don't have to use external hardware (line level converters and microcontrollers) to hook the LCD up. The disadvantages are numerous: more difficult to write programs for, slower, non-standard (there are four different "types" of parallel ports, from a programmer's perspective), and a lot more wires to deal with. It's usually worth the trouble to hook up a microcontroller and use serial.

In the near future I plan on not only releasing schematics and circuit board layouts for a serial adapter, but also selling (at a reasonable cost) ready made boards. Perhaps this could be a good way for Smartie to make some money off of an otherwise "free" program.