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Topic: Anyone modded their Mega2560 for 3.3V operation? (Read 471 times) previous topic - next topic

Retroplayer

If so, I am wondering if it became unstable after doing it.

I am considering a hack where I can switch between 5V and 3.3V operation since it is a PITA to have to keep adding CD4050s to my breadboard to talk to 3.3v stuff. It seems like everything I am working with lately is 3.3v. But I would like to retain the 5V function just in case (since using a 5V device on a 3.3V arduino would likely damage the Arduino.)

Anyway, just curious if anyone has tried this. Obviously the "recommended" voltage for 16MHz operation is 5V, so that is my biggest concern.

retrolefty


If so, I am wondering if it became unstable after doing it.

I am considering a hack where I can switch between 5V and 3.3V operation since it is a PITA to have to keep adding CD4050s to my breadboard to talk to 3.3v stuff. It seems like everything I am working with lately is 3.3v. But I would like to retain the 5V function just in case (since using a 5V device on a 3.3V arduino would likely damage the Arduino.)

Anyway, just curious if anyone has tried this. Obviously the "recommended" voltage for 16MHz operation is 5V, so that is my biggest concern.


Well it should work. The Seeeduino folks sell a mega boad that has a 5/3.3 selector switch. It is exceeding the ratings running at 16Mhz @ 3.3vdc, but many people do that with having problems.

http://www.seeedstudio.com/depot/seeeduino-mega-p-717.html?cPath=132_133

Lefty

Retroplayer

That's what I had heard as well.

Holy Crapola! $43 for the SeedStudio board? Wow... I think I will try hacking my own first.

oric_dan

I haven't done it with a Mega2560 chip, but for the past year, I've been running the 328
chip at 16Mhz and 3.3V, and the past month been doing same with the 1284P chip. And
no problems, although against all warnings - of course. If you interpolate the operation
curves, they actually show 13.3 Mhz at 3.3V, so you're only overclocking by 20%.

Also, for hacking, the 40-pin DIP 1284P chip is a nice choice inbetween the 328 and 2560,
and lots easier than tiny smt pins. You get 32 I/O pins.



Retroplayer


I haven't done it with a Mega2560 chip, but for the past year, I've been running the 328
chip at 16Mhz and 3.3V, and the past month been doing same with the 1284P chip. And
no problems, although against all warnings - of course. If you interpolate the operation
curves, they actually show 13.3 Mhz at 3.3V, so you're only overclocking by 20%.

Also, for hacking, the 40-pin DIP 1284P chip is a nice choice inbetween the 328 and 2560,
and lots easier than tiny smt pins. You get 32 I/O pins.


I actually ordered one the other day. It is in the mail.

I am actually not all that impressed with the pin mapping on the ATmega2560. I like to do a lot of tricks reading an entire port with a mask or writing an entire port at once and the way they pin-mapped this, it is all over the place to make it work with existing shields.

Good to know about your experience with the 1284 as I was planning to do just that with it.

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