Hi Dave,

Arduino is not AMICUS18 and XINO is not Arduino - simple as that. I looked at the datasheet for the ATMega 328 which I believe is what is used on the Arduino. It operates on anything from 1.8 to 5.5V so THAT won't be a problem. If the Arduino contains a voltage regulator and the option to actually RUN it at 3.3V instead of 5V is another question.

I think it, in the end, boils down to this: Either you make these shields of yours compatible with "everything" that happends to have the same same board shape as the Arduino, meaning you include voltage regultors and level translators or you don't.

If you don't want voltage regulators and level translators on the shield(s) then the decision is made: Your shield will work with boards operating at 3.3V, which is good because that's what the AMICUS18 does. It won't directly work with boards running on 5V.

One possibillity is to include foot prints for voltage regulator and level translators and more pads allowing them to "wired in" but then it'll soon start to look like a breadboard and not a "plug and play shield".

/Henrik.