Found this in manual:
VDD_5V is the main power supply from the DC input jack. This voltage is not present
when the board is powered via USB. The amount of current supplied by this rail is
dependent upon the amount of current available. Based on the board design, this rail is
limited to 1A per pin from the main board.
The SYS_5V rail is the main rail for the regulators on the main board. When powered
from a DC supply or USB, this rail will be 5V. The available current from this rail
depends on the current available from the USB and DC external supplies.
and:
DO NOT APPLY VOLTAGE TO ANY I/O PIN WHEN POWER IS
NOT SUPPLIED TO THE BOARD. IT WILL DAMAGE THE
PROCESSOR AND VOID THE WARRANTY.
NO PINS ARE TO BE DRIVEN UNTIL AFTER THE SYS_RESET
LINE GOES HIGH.
I´m not sure what it means.
Have I use 5V on VDD or SYS?
And when I try to use an input, I must boot the BBB before the Input Pin is going high? This is unpossible. Because when the Input is high and the BBB lost Power it damaged?
Thanks for helping a newbie!