Re: [avr-chat] STK500 LEDs

[Graham Davies]

Gavin Jackson wrote:
> This is the standard way for driving LEDs, the micro
> can sink more current than it can source ...

This isn't really true.  From the data sheet of the ATmega16, for instance, 
you can see that the outputs can source very nearly as hard as they can 
sink.  In my opinion, this low-for-ON choice is a harmless holdover from the 
days of TTL current sinking logic when outputs could most definitely sink 
more than they could source (hence "current sinking").  As CMOS took over 
from TTL, threshold levels were retained for compatibility and the designs 
of the output stages were quite artificially warped towards current sinking. 
Today, however, you will often find outputs to be powerful sources of 
current as well as sinks.

Graham.