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Topic: Mega Junior,1284 (Read 20 times) previous topic - next topic

white-eagle

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?

oric_dan

#121
Jul 23, 2013, 07:43 pm Last Edit: Jul 24, 2013, 07:40 pm by oric_dan Reason: 1
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.

white-eagle

Has anyone tetsed the analog comparator on the board?

I can't get it to work properly.

pito

1284p runs fine @16MHz and 3.3V.

Docedison

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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CrossRoads

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
Designing & building electrical circuits for over 25 years. Check out the ATMega1284P based Bobuino and other '328P & '1284P creations & offerings at  www.crossroadsfencing.com/BobuinoRev17.
Arduino for Teens available at Amazon.com.

white-eagle

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  :)

Only question remaining is about the analog comparator that doesn't seem to work.

oric_dan

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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