RE: [avr-chat] STK500 LEDs

[Gavin Jackson]

>I am confused by the response of the LEDs on the STK500. It appears to
me 
>that sending a logical high turns off the LED, and sending a logical
low 
>turns it on. Is this how they are meant to work? (I know that pressing
the 
>switches drives the input pin low, so I suppose this is conceivable.)

This is the standard way for driving LEDs, the micro can sink more
current than it can source, so the anode of the LED is connected via a
resistor to the supply line while the cathode is connected to the
micro's port pin. A logic high prevents any current flowing through the
LED and thus no light, while a low permits current and produces light.