First, relax, you're 1000x better off to ask first. LK204-25 needs a modified power cable. Just to make sure you can take that with confidence, here's the relevant manual: http://www.matrixorbital.com/manuals/lk20425/index.htm Specifically, check out section 1.4. Things change a bit if you got the w...

That's what he's doing. That capital N is the 0x4E in the sprintf string.

What I see looks good. I'm guessing you've looked over the Display.pm you can download from MO.

The only thing I wonder about (based on what you're showing me) is display_text(). Does

print DISPLAY ""$char\n";

work at all? I can't see what display_text() is doing obviously.

clean! Impressive work for sure.

Per the USB 2.0 spec, you don't worry about the length per se, you worry about the signal pair attenuation and propagation delay. Since the speeds at which the MO displays operate are so low (compared to USB 2.0), I'd expect 5m to be no problem in practice. Buy a USB 2 rated cable for best results b...

Try it using LCDC's test mode--it will echo keypresses for sure.

LCDC is a pain to configure until you get used to it, but so is pretty much any powerful program. I can give you some quick advice for the things that don't seem to work--you probably don't have necessary plugins enabled for those variables (at least that's why you may see a bunch of $FOO variables ...

Yep, no problem. I've got one hooked up just like that in my mouse.

I'm too colorblind to tell you if those bands are the right color but 100 ohms is right from the 3.2V @ 20 mA. Is your LED red? 3.2V @ 20 mA seems high for red. (Probably OK anyway.) The other thing is you may as well just use a molex connector from your PSU, unless you have some sort of switch to p...

LED == Light Emitting Diode.

IF you want to hook an LED to your power supply, you have 5V (red) and 12V (yellow) available. Both require a resistor to limit the current to your LED.

To size that resistor, you need to know the diode's rated forward voltage and current, and plug them in here: http://www.bit-tech.net/article/68

I was looking at the events just now, and I can't immediately see how you would get the amber combination since there's no logical AND. My head hurts from thinking about it though. Okay, I guess it would really be just two overlapping windows: The green side would be on above some floor (say 0) and ...

Actually you could use both GPOs to drive a tricolor LED: one GPO lit = green, other GPO lit = red, both lit = amber. That would be pretty tricky.

(Sorry if that confuses you, I know you said you were an electronics n00b.)

Right, sorry I missed that detail. Green and red then.

You really wouldn't need to use a GPO for a power on light, because like you say, wiring it straight to the PSU wold be equivalent. Are you running LCDC? There's a lot of cool events that could map to GPOs turning on/off, like temp thresholds, CPU usage thresholds, all kinds of madness. How about a ...