3.3v Arduino vs 5v Arduino:
- Uses different boot-loader, need to select in Arduino programming environment: Tool/Board -> Arduino Pro (3.3v / 8Mhz) w/ATmega328
- Boot loader is larger! 3.3v leaves 30,720 bytes available to use vs. 32,256 in the standard 5v Arduino
- Struggles with higher serial port rates. I had lots of trouble communicating reliability with the RN41 Bluetooth at 115,200 baud, specifically receiving. O'Scope showed no problems with the signals, but a Google turned up that even at 5v the Arduino is on the edge for 115,200. (I have backed off to the nice solid 9600 baud)
- 3.3v / 3.6v Zeners have terrible characteristics. Under 5v, and Zeners use a different physics to work, with a resulting poor knee. This continues to cause issues around protection, and I will be looking to likely pull them all out... (More on this in a later post) (And ya, this is not really an Arduino issue I know :-)
- Will not support watchdog resets! Still need to dig into this, and hope I do not need to come up with custom boot-loader.. Right now I have a workaround for forced reset of the controller (ala, after receiving config changes via the Bluetooth), but IF the watchdog triggers - rather then rebooting, the systems halts and needs a power cycle. At least it will take down the Field FET drivers, so the battery / alternator is protected! But I do want to fix this down the road.
Maybe that is it for now. If I find anything else out, will update this list.