Best Way to hook up a hd44780 w/o a parrallel connection

[briant]

Hello,
So for the longest time I've had a hd44780 lcd that I scrapped from an old pc. The Display already has a parallel port (db25) connector cable attached to it and a 5v power supply. I have gotten it to work with lcd smartie on a old computer with an actual db25 parallel port built in to the motherboard, however my overall goal is to get this running on a fairly new computer with windows 7 64 bit, and does not have a built in parallel port. So far from looking around this forum, I found out that a usb to parallel port will not work because it only supports printers. However, in addition to one of those, I have a usb to db-9 (serial) cable and a db-9 (serial) to db-25 (parallel) adapter. Is it possible that my little db-9 to db-25 adapter will work? I have tried that using lcd smartie and the hd44780 display plugin and selecting com1 (the usb serial cable) instead of lpt1. However that does not work. I have also found a interesting plugin here that looks like it is a modified hd44780.dll to support serial. I tried that one too, and that does not work ethier. Anyway, is there any possiblity i can get this to work with a usb to serial cable? Or does anyone know a better way to get this to work without anything too complicated? Thanks is advance.

[mattcro]

That DB9 to DB25 cable is just a serial cable, not a parallel-serial adapter. The really old serial ports used DB25 connectors, before DB9 connectors became the standard.

For newer PCs, the only option is USB. There are several projects mentioned on this forum to connect HD44780 LCDs to USB... http://forums.lcdsmartie.org/viewtopic.php?f=11&t=1540 is one (might not work well with Win7/64 though), http://forums.lcdsmartie.org/viewtopic.php?f=11&t=833 is another, and you can also use the LCD2USB adapter kit with Smartie. Another way is to get/make a serial to LCD kit and use a USB-RS232 adapter.

If you can find a cheap PCIe parallel port adapter, you can use that under Win7/64. There are a few threads on this form about that too.

[briant]

That DB9 to DB25 cable is just a serial cable, not a parallel-serial adapter. The really old serial ports used DB25 connectors, before DB9 connectors became the standard.

Dang, so it will just not work with that period? Oh well.

For newer PCs, the only option is USB. There are several projects mentioned on this forum to connect HD44780 LCDs to USB... viewtopic.php?f=11&t=1540 is one (might not work well with Win7/64 though), viewtopic.php?f=11&t=833 is another, and you can also use the LCD2USB adapter kit with Smartie. Another way is to get/make a serial to LCD kit and use a USB-RS232 adapter.

Hmm... I just looked up the lcd2usb boards on ebay, and they look very promising. I just have 2 questions.
1: Does the usb method require an alternate power source? What I mean by that is can the 5v of power recuired for running the display come from the usb connection? If so that would be great!
2: From the description it looked like some soldering is required. Is this correct and if so what exactally do I need to solder? The description here was a litle confusing for me, so i would greatly appricate some help. Thanks. Let me also explain the part that was confusing

8. Photo show solder short jumper for our LKC-2004-B3/C3. Please take a look LKC-2004-B3/C3 's pin out in specification. Use hole 3 to hole 18 of CN1 for single controller LCD connection. SJ1 to SJ4 are for backlight polarity, SJ5 to SJ8 are for power polarity.
For single controller LCD pin 15 = LED + and pin 16 = LED - ->(SJ1 short, SJ2 open, SJ3 short, SJ4 open). For LCD pin 15 = LED - and pin 16 = LED + -> (SJ1 open, SJ2 short, SJ3 open, SJ4 short).
For single controller LCD pin 1 = VSS and pin 2 = VDD/VCC -> (SJ6 open, SJ5 short, SJ7 short, SJ8 open). For LCD pin 1 = VDD/VCC and pin 2 = VSS -> (SJ6 short, SJ5 open, SJ7 open, SJ8 short).

I probably will go with the lcd2usb method, if someone can clear things up for me. Thanks again.

[mattcro]

Is this the LCD2USB module you were thinking about? http://cgi.ebay.com/USB-Characters-LCD- ... 33645eb351

You will need to do some soldering. You have to connect the LCD to the controller board with wires or optionally a pin header as shown on the LCDModKit page (only for LCDs with a 2x8 way connector). You also need to put a small blob of solder on some of the jumper pads to set up the board for the LCD pinout.

The USB port supplies the power for the LCD and backlight, so you shouldn't need a separate supply, except maybe for large LCDs like 4x40.

The exact connections and solder jumper settings depend on your LCD module pinout. The typical LCD up to 4x20 characters has the pinout shown in the top diagram on the Smartie wiring page here: http://lcdsmartie.sourceforge.net/circuits.htm What size/model of LCD do you have?

If your LCD matches this wiring then you can use these settings:
For single controller LCD pin 15 = LED + and pin 16 = LED - ->(SJ1 short, SJ2 open, SJ3 short, SJ4 open)
For single controller LCD pin 1 = VSS and pin 2 = VDD/VCC -> (SJ6 open, SJ5 short, SJ7 short, SJ8 open)

You just solder a little blob onto the required jumpers (the ones marked "short" above) to bridge between the pair of pads. You can just about see this in the photos on the ebay page I linked to above.

[briant]

Is this the LCD2USB module you were thinking about? http://cgi.ebay.com/USB-Characters-LCD- ... 33645eb351

Yep, That's the one.

You will need to do some soldering. You have to connect the LCD to the controller board with wires or optionally a pin header as shown on the LCDModKit page (only for LCDs with a 2x8 way connector). You also need to put a small blob of solder on some of the jumper pads to set up the board for the LCD pinout.

Perfect! My LCD already has a 2x8 pin connector already attached to the back of it.

The exact connections and solder jumper settings depend on your LCD module pinout. The typical LCD up to 4x20 characters has the pinout shown in the top diagram on the Smartie wiring page here: http://lcdsmartie.sourceforge.net/circuits.htm What size/model of LCD do you have?

If your LCD matches this wiring then you can use these settings:
For single controller LCD pin 15 = LED + and pin 16 = LED - ->(SJ1 short, SJ2 open, SJ3 short, SJ4 open)
For single controller LCD pin 1 = VSS and pin 2 = VDD/VCC -> (SJ6 open, SJ5 short, SJ7 short, SJ8 open)

The size of my LCD is actually a 2x20. Does this change anything? I don't know the exact model of my lcd, but it looks a lot like the LKC-2002-B2, found here

Also I have 2 more questions after rereading the ebay page.
Are the jumpers on the LCD2USB Board pretty well marked? I just wanted to ask because I couldn't tell from the pictures.

What is the difference between a single controller lcd connection vs a dual controller lcd connection? After looking again at the ebay page, I noticed it talked about the 2. In picture 8 it talked about how to solder a single controller LCD connection, while in picture 9 it talked about a dual controller LCD connection. How do I know which one I have?


Again, Thank you very much for helping me.

[mattcro]

The dual controller settings only apply to 4x40 LCDs. They have 2 of the standard controller chips, and each chip handles half of the display. Your 2x20 will only have a single controller.

I don't know much about the LCD2USB system and have never used it, so I can only give general advice.

There are much bigger photos on the LCDModKit site, and you can see the jumpers clearly there... You should be able to do the soldering as per section 8 on http://www.lcdmodkit.com/module/BPU204A-1.html

[briant]

The dual controller settings only apply to 4x40 LCDs. They have 2 of the standard controller chips, and each chip handles half of the display. Your 2x20 will only have a single controller.

Oh, I get it. Thanks for that useful info.

I'll probably order 1 of these tomorrow.

Thanks.