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Can usb ports share a ground?
Im converting an old printer (25 pin) switchbox into a switchbox that will be used for my monitor, speakers, keyboard, mouse and two computers. The problem is that the monitor has 15 pins, the speaker has 3 pins, and the two usb ports have 4 pins each meaning that I would need 26 pins rather that 25. I could just solder the left and right speaker pins together and make those two 1 pin, but i would rather not have to do that. My question is can two usb ports share a ground pin, meaning that it would only need 7 pins rather than 8.
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7 years ago
Usb doesn't really have a ground, it has a negative. But It should be okay to connect the negatives together.
but there is really no need to do that. VGA has 4 pins that don't connect to anything. Check out the vga pinout in this link. It's down in the middle of the page.
7 years ago
Its more than likely that they share the same +5v power connection too but they almost certainly can share the same GND connection.
Are you certain that the monitor uses all 15 pins?
Not a good idea to just join the two speaker pins together.
Better make sure that the printer switch does switch ALL 25 connections because the old Centronics 25-way printer connections had a lot (probably half) of the connections were all Ground and so probably not included in the switching. If this is the case then you are out of luck - you'll probably have about 8 to 10 switched connections to play with and you will have to start thinking about sharing a lot of the grounds not just the two USB grounds.
Good Luck