Here's what I think I would need. The project would require 10 of these boards.

Im dusting off this old project of mine that requires ten(10) LK204-25s to be linked together. Is I2C the most economical way to go?

I haven't purchased the LCDs yet, so I could go the USB route.

It would also seem that I2C would be easier to implement in software, since only one connection ...

Sorry to revive this old topic, but my project has been put on hold for a while. Recently, there has been a renewed interest around here, so I will be picking up the pieces very soon.

Let me preface this by saying that I very much appreciate everyone's help. My expertise is in software engineering ...

Thanks Stig & linear. :D Here's what I did...

With the GPOs unplugged, I applied 5v to point A to test the transistor thingy. (If your drawing in the earlier post doesn't have labels, please hit your refresh button.) The lamp came on, but it was very dim. So I placed another 4.7K resisitor in ...

Well, I tried building the circuit but it didn't work. :-?

Here's how I wired it up on the breadboard:

http://jcent.com/LampCircuit.jpg

I know that the GPO output is working because a used a LED to test it. My transistor is a TIP31C, instead of a TIP31A. Would that make a difference?

The ...

My LK204-25 has a 10 pin, single row header which represents a 5x5 matrix used for inputs. I plan on using a 4x4 keypad which plugs in nicely to the middle 8 pins. But suppose I want to use the other 9 remaining keypress combinations for other inputs. What is a neat way to piggyback onto the header ...

That sounds very interesting. I WAS thinking about using an I2C bus to link together the 10 displays needed for my project. But if a LK204-25 w/USB will be available in 3-4 weeks, then it might be simpler for me to just wait. I was going to use a USB to I2C bridge anyway.

Can the new displays be ...

OK, I'm going to order the components this week to build a few of these circuits for testing with my project. Are the TIP31A transistor and the 4.7k resistor adequate for a 6 volt , 0.25 amp load? The circuit designer claims that he can handle 3 amps at 12 volts. Any problem with using a lower ...

After studying the BayBus circuit, I am a little confused about one thing. When the GPO is OFF (i.e. the negative pin is NOT grounded), where does the base (B) voltage come from to switch on the transistor? Thanks for the help, and please excuse my electronic ignorance.
:D

In short the circuit ...

thanks linear, that's just the info that i was looking for!

My project involves multiple LK204-25 LCD displays, each controlling several small lamps. The lamps are GE 555 bulbs, 6 volt, 0.25 amp. I have a separate power supply for the lamps, but need a switching circuit that will work with the GPOs. The project will require about 30 lamps and thus 30 GPOs ...

You can use USB to serial converters and a VCP

Uhhh...what's a VCP?

I need to hook up ten displays to a laptop, so I thought I2C would be the way to go.

I found this $79 USB to I2C interface board on the web and was wondering if anyone has ever tried to use it with Matrix Orbital's LCDs.

Henry, if you have a few seconds, could you take a look at the specifications on their website to see if it looks viable? The features listed include "90Kbps I2C ...

I have a project that is going to require ten independent LK204-25 displays. I would like to know my options for wiring them to a single serial, parallel or preferably USB port.

Each display would need to be addressable so that the software can update each independently. Each display will also have ...