I have a i2c device ( Nintendo wii -remote ) with this pinout. It is a handle held battery operated device.
I want to interface it with my atmega32u4 but I need this device above (power source two batteries 3v) to power the mega chip and I need to allow bi directional communication. This is normally an easy task with a simple level shifting logic and a 5 volt input but in this case I do not have 5v. So my fist though was a boost to get the 5v with a mosfet to do the normal logic shift. However I'd like to not have so many components on this. I'm pretty certain this is a 2.0 i2c bus and I read the first gen i2c used 5v but 2.0 requires no more then 2v. So I may need to use one of these.
Though this wii-mote created by Nintendo may not have followed any i2c rules.
Also, i'm wondering if the two batteries will be enough to power the mega chip and if so will it last long? I think An AA battery can do more than 1A but they'll discharge fast, in about half an hour. Though a mega32u4 only pulls a few milliamps, that boost may require a bit more.