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Author Topic: USB Power - Common Ground?  (Read 519 times)
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Hi all,

I'm adding USB connectivity in a design I'm working on, but don't wish to provide 5V from the USB port/cable itself as I've got 5v and 3v3 regulated on the board from a 12V supply.

However, do I still need to connect the ground pin from the USB port/cable to the boards ground?

Cheers!
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Yes.   The USB data lines should have a common ground.
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the land of sun+snow
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You always need a signal ground for reference. Your board will not draw power
off the USB port as long as you don't connect the USB power pin to your ckt. Your
board will be much more capable if not drawing 5V and 3V from the USB port.
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Even though USB is a differential protocol, which gives the data lines a virtual ground, out of band signaling like JK chirp require a ground reference.

So yes, you need to connect ground.
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Thanks for all your replies, that's certainly answered!
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