I'm looking in creating a project using the atmega32u2. This design will have multiple uses. But in all cases it will run off power from various gaming console controller ports.
source usb: I.e xbox. this will be usb voltage so in this case not really issues. The chip will run as a usb device within the operating voltage.
source +5: Most all consoles will supply 5 volts, and the current rating will go from 20ma to 400ma. As long as it can power the mcu (don't see why not) this will be ok.
source +3.3: This case I'd need to step up my voltage. This mode require specific timing with a 16mhz crystal and 3.3 is outside the acceptable clock range for the chip.
There is one more brick I need to throw in here. This device will also have to power a atmega328. and a controller. The 4 devices will be linked together.
[1 controller]->[2 device using atmega328]->[3 this device atmega32u2]-> [4 console]
So 1,2 and 3, all need to depend on power from 4. The total current is :
1 most controller range from 5 to 20 ma. I have see some a bit higher
2 atmega328 6.75mA @ 5 volts
3 guessing a bit more then the 328
4 20-400 ma depending and some combination will just not work.
This is the reason I said "feasibility" and I know a lot if detail is left out here as I don't have data for all possible scenarios. I'd like to achieve this without a battery or having to use an additional voltage source. As it stands my main concern is the 3.3 or any other scenarios where the MCU may require more then the supplied current. One option is to use the pololu device, http://www.pololu.com/catalog/pr... but would that work out well enough? Most of what is going on here is logic level switching and the occasional controller motor turn (i.e rumble). Though the timing in the mega328 is very critical so I must maintain 5 volts at all times.
The easy solution here is stable power from an external source. I guess my question is, is this feasible without an external source, or is it way to hard to tell without experimentation? Only brainstorming ideas here, if there is no solution to this, ill opt for the external power source.