>> The page also claims that you can configure an output pin to drive an 
>> LED so that it lights when the pin goes *low*... Man, electronics is 
>> weird!
> 
> Why is that weird?  The LED doesn't care which leg is connected to the 
> logic output pin, it's just a voltage.  You could even connect the LED 
> between two output pins*, then it would only turn on when one was high 
> and the other was low.

I always thought of it as logic high meaning "connected to the +V rail" 
and logic low meaning "not connected to anything". From the looks of 
things, it seems that actually logic low means "connected to the -V 
rail". So it's like a bipolar setup...

> * Using a series resistor if required...

Yes, that's the other fun thing. Depending on which type of gates you're 
using, they supply about 20 mA. But some of the LEDs I'm looking it draw 
40 mA...

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