I have my Pi 3 powered over the 40 pin header, and my project makes use of all of the GPIO pins.
Is there a good way to tell just over the 40 pin header whether the Pi is powered on? I figured it could be possible to tell through power consumption or something similar. I'm trying to use this information to control the Teensy & relay I'm using to turn it on and off.
Is it possible to turn it on and off also just via the 40 pin header and skip the relay? I remember there was a reset pin, which should be usable to turn on a powered off Pi since application GPIO pin mappings only take effect once the Pi is started/the application loaded afaik? I found examples for how to restart and shutdown but not power on.