I have a Odroid-U3 minicomputer where its USB VBus and Ground pin are shorted, making the USB ports unusable.
But I was able to make a workaround. What I did was used an external power usb hub, taped the VBus pin to the USB plug to be connected to the USB Host (Odroid), and let the external power supply power my peripherals.
Now, I have one power supply powering Odroid and another to power the peripherals but they share the same ground.
It works but is it safe to let them share the same ground or since the data is transmitted via differential signals, ground is not needed?
EDIT:
Here is the current schematic diagram of my odroid setup:
Also, there is no connection between the Vbus of the USB port on odroid to Vcc of the system power supply.
Best Answer
It's completely safe to ground both circuits together, and there's no need to add any high impedance resistence between sources. Actually, adding this resistor would only lead to increase in power consumption. It's important to understand that the goal of attaching both ground it's to maintain equal electric reference among both circuits, otherwise you could create hazard difference of potential between the circuits which could lead to damages.