Seeeduino ADK I/O @ 3.3v? 16Mhz @ 3.3v?

Bought a Mega ADK awhile back not realizing that it was a 5v only type board? Also didn’t realize that the Mega2560 isn’t spec’d to run 16Mhz @ 3.3v.
Couple questions before I buy the Seeduino ADK…
(Relatively new to the Arduino environment. Coming from an exclusively PIC background since ~1995.)

  1. Searched and saw some posts from a few years back talking about seeing 4v on the I/O lines when the 5/3.3v switch in the 3.3v position. While it didn’t apply to the ADK board, is this, or has it ever been, an issue?

  2. With the switch in the 3.3v position, can you still connect and reprogram via the USB cable? Or do you have to use a 3.3v capable ICSP programmer?

  3. I assume that the '2560 is still running at 16Mhz even with the switch set to 3.3v. According to the datasheet, this is ‘out of spec’. On my Mega ADK board, I can run a ‘blinky LED’ at 16Mhz down to about 2.96v before it starts to fail, but since there’s no real ‘work’ being done, I think I could assume the board wouldn’t be stable if driving any kind of external loads on the I/O pins. I think I could further assume that at 3.3v, the '2560 is much more stable, even though it’s being run ‘out of spec’ (that is if it’s still running 16Mhz).

  4. Assuming there aren’t any unknown issues, the Seeeduino ADK is functionally 100% (but not quite physically 100%) compatible with the official Arduino Mega ADK board?


That’s ok.
I didn’t want a Seeeduino ADK anyway.