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.)
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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?
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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?
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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).
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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?