I'm owning a Rasperry Pi3
I want to disable automatic boot when plug in power cable. I don't want to use a simple mechanic switch because I want passive power still avaible for the board for various reasons.
I couldn't find a solution. I wouldnt' have had any problems soldering stuff because I already added a power button for shut down/restart the pi
You can connect to two pins of the RUN header to keep the Pi3 in reset and thus not booting.
See here where this connector is:
The two pin "run/reset" header seems to have moved [..] to the other side of the 40 Pin GPIO connector between that and the outermost Pair of Stacked USB connectors
Function of the RUN pin explained for the Pi2 here. I reasonably expect the same behaviour for the Pi3.
It is also unlikely to damage the Pi by keeping it in reset indefinitely, see here.
