Using VIN and USB power at the same time

Hi, I have a project where an MKR1000 is hooked up to a Drone's flight controller. The flight controller provides regulated 5V power to the MKR1000 via the VIN pin which works great.

I am wondering if there would be any problem plugging in USB without disconnecting the VIN pin?

There are two cases, one with the flight controller providing 5v to VIN (ie: battery connected) and the other being with no battery connected to the flight controller, so no voltage at VIN but the pin is connected to the 5v out of the flight controller, which is shut down.

I'm just wondering if the power circuitry on the MKR1000 would leak any current from the USB side into the output of the Flight Controller's regulator, possibly damaging it.

I think the answer is probably "no problem" but thought it would be worth checking.

Whilst I haven't done it with my MKR's I have done it with other Arduinos and have not had any issues whatsoever.

The only time I have been careful is when setting up Ardi Micros where I have them powered by VIN and I just don't use the VCC on the serial adaptor. (chinese clones)

And if you think about it the JST is also doing a VIN for LIPO's

If you look at page 2 of the PDF schematic you can see how the power scheme works

Its pretty well protected.

It will use the highest voltage power supply automatically. No problem at all powering it from more than one supply