Is the DUE is using a compatible shield footprint as the Uno/Mega?
If so, Is the DUE 5V tolerant on the inputs?
Or are users potentially going to be burning up inputs when they attempt
to use their existing 5V shields on the DUE?
In other words, if the DUE is backwards compatible with existing shields,
how do you prevent users from damaging their DUE when plugging in 5V shields?
--- bill