I am working on a project with a variant of the Arduino DUE - the Macchina M2 specifically. I have this in my Porsche and it runs the gauge cluster with CAN info from the GM LT1 (Gen V 6.2) I have stuffed in the back. Initially I powered the M2 on a switched ignition source. The issue I seem to have is the M2 boots a little slower than the other systems in the vehicle, and when it isn't transmitting on boot up, errors start to pop up on other controllers. So from there, I started to look into other options.
A) Boot the M2 quicker. I don't know much about this, afraid to mess with it to be honest. Not even sure where to start.
B) Connect the M2 to battery directly - Easy for wiring, but I couldn't get the M2 to power down to less than ~50mA in sleep states. Obviously, not a good idea to have a drain that high on an idle battery.
C) Find an an earlier power source - When the door opens, or key is first inserted. Most systems in the car that turn on when the door is opened have a battery supply and use a 12V signal that "wakes" them up. I tapped this signal, but it is not meant to be a power supply... It didn't power the M2 at least. So now this stems to my thread title, my thinking is that I can use this 12V "wake-up" to trigger a MOSFET that powers the M2 from a battery source. Something like my picture below.
EDIT: If you are interested in more on this project in general, I have the M2 side partially documented here:
And the actual car build well documented here: