Powering up and down USB

[MarkHaysHarris777]

Please see this schematic, page 9 of 19


You will notice that the two regulators EN line(s) ( similar to the Rock64 regulators ) are tied directly to Vcc-5v|usb-5v;  consequently the regulators are ON all the time.

If you look at the PMIC page ( power management integrated circuit ) you will see on the left bottom that the usb-5v is tied directly to Vcc-5v;  and you will further notice that the Vcc-5v is tied either directly to DCIN ( 5v ) or the 5v regulator from battery based on the  DC5v-Batt power jumper ( PMIC page top left ).  

So the bottom line is that the usb 5v is always ON based on a physical jumper setting;  however,  this is where it gets interesting !

... because the jumper doesn't have to be a physical jumper connector;  it can also be a relay ( or electronic switch of some kind ) that is activated via gpio(s) !   So, although the board is not wired internally for this support ( like the Rock64 is ) it is wired to be allowed via external control because of the DC5v-Batt power jumper !