Why is the LED (13) driven by an OpAmp?

Hey all,

It might be clear to some of you, but why is the LED13 driven by an OpAmp? In all examples, a LED is simply added with a resistor, but the official Arduino schematics show it with an OpAmp.

I've read some guesses: "using left over port on OpAmp", "power drainage"... but that doesn't help much.

Your opinions?


So you don't load the pin. This is a dual use pin, you can use it for the LED or anything else. The SPI library uses it for the SCLK. The op amp makes sure you can put the full digital load on the pin.

In particular it keeps the pin high enough impedance to work with external pull-ups and pull-downs.