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Author Topic: Mega Junior,1284  (Read 11490 times)
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The board now works fine. Great to have 128k of memory.

Next step is I want to have a board running at 3.3v. Max CPU frequency in that case is 10MHz.
How do I create a bootloader that works at 10 MHz?
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the land of sun+snow
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If you look closely at the actually frequency curve in the d/s, you'll see you can "officially" run about 13Mhz at 3.3V.

Despite many people's dire warnings of gloom and doom over the past year, I've been running my 3.3V megas at 16 Mhz for over a year and a half.
« Last Edit: July 24, 2013, 12:40:53 pm by oric_dan » Logged

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Has anyone tetsed the analog comparator on the board?

I can't get it to work properly.
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Rapa Nui
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1284p runs fine @16MHz and 3.3V.
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Anyone ever use a Mega 2560 @ 3V3 and 16 MHz?.. I'd sure like to. It would make a thing I'd like to build about 1/10th the work If I didn't have to 'mess' with providing interfaces to the GLCD and various radios and other sensors from 5 to 3V3.

Doc
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Atmega2560 is not rated to work at that low a voltage:

ATmega2560/ATmega2561:
• 0 - 16 MHz @ 4.5V - 5.5V

You need to use Atmega2560V to go that low:
ATmega2560V/ATmega2561V:
• 0 - 2 MHz @ 1.8V - 5.5V, 0 - 8 MHz @ 2.7V - 5.5V

http://www.digikey.com/product-detail/en/ATMEGA2560V-8AU/ATMEGA2560V-8AU-ND/735456
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Docedison, the 2560 is of topic. perhaps you should start a separate post for that.

My 1284 also works fine at 16MHz @ 3.3v, so problem solved  smiley

Only question remaining is about the analog comparator that doesn't seem to work.
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the land of sun+snow
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I've never tried the analog comparator on any of these chips, but the problem is probably just in getting all the registers set properly. If you're relying on existing code from another processor, that might need some mods for a 1284.
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