USB Switch with SPDT

_4_ SPDT switches?

Why not just use a crossover Ethernet cable and share the drive on the host machine?

Well the problem is that one of the machines is a custom computer board in development and it has no ethernet support as of now.

keep the D+/white and D-/green wires twisted for as much of their length as possible.

istm you may need to ensure that the power terminals (ground/black and +5/red) are connected first and disconnected last as the plugs are designed to connect the power terminals before the data terminals.

Bye. Jasen

The D+/D- lines are a matched and controlled impedance transmission line. I would say that your switch and wiring are interfering with these lines.

I'll assume that you are using Windows somewhere along the way ;-)

Unfortunately, Windows (even XP) doesn't always deal well with USB disconnect/reconnect. You'll have fewer problems if you always use the "Remove Device" right-click on the USB icon, but even that doesn't work all the time.

If the hard drive is a high-speed (480Mbps) USB device, there's a very good chance that taking the relatively well-controlled (impedance- and balance-wise) USB cable and running it through some random wiring and a switch will degrade the signal enough to prevent a proper connection between the PC and the device.

At full-speed (12Mbps) I wouldn't expect problems unless you've got a *lot* of random wire flailing about, though.

Personally I'd just go buy a commercially made switch for this purpose: They actively buffer and re-transmit the USB data as needed.