Im new to the APM community, and I think its fantastic. Im trying to evaluate using the APM 2.5 as a multi-camera controller and AHRS logger.
However it needs to run at 3.3v, since my power source is coming from a Li-Ion source and I would like to avoid using a step-up circuit to 5v, since my I/Os need to work at 3.3v.
On looking at the schematics, and these are my conclusions regarding using the APM 2.5 at 3.3v:
-Get a regulated 3.3v supply and feed it to VCC on any of the output pins (Keeping JP1 on). [My limited cognition couldn't think of any way to hack the on-board 3.3v regulator to use provide this. What do you guys think?]
-USB power: Get rid of fuse F1, and keep it floating, so the +5V from the USB doesnt go to the 32U2. [It could also be sent to the input of the (off-chip) 3.3v regulator to get power from USB].
-Run both the Atmega2560 & Atmega32U2 @ 8Mhz, by setting the prescaler CLKPS to 1. [Keep CLKDIV8=1 for init ; No need to put in a 8Mhz xtal].
Im wondering if this should do the trick, what its limitations will be and what Im missing. Im looking at you champs to throw some light.
Thanks a ton in advance!