Using the APM 2.5 at 3.3v

Hi All,

  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!



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  • I have a APM2.5 blow the UART 2 chip has a tiny pinhole on its surface
    could it be that the lipo gave too high voltage with JP1 on
    I did try to connect the USB to my PC at the same time that the lippo was powering the ESC

    could this be a consequence of what you are describing above...just to help others not to blew their boards the absence of instruction are not clear about the supply only wikki and blogs
    I am very disappointed with the protection of this board and then it should clearly state to use 3.3 v
    will be looking for some other board....even if I have to use old fashion shield.....
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