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I am looking for a device that connects to two USB ports on a computer: a "Control" port, and a "Data" port. Both cords go to the same device, which also has one USB "out" port (3 ports total). If a certain signal (from whatever driver is loaded for it) is sent to the device from the "Control" port, it should, depending on the signal, physically connect or disconnect the "Data" port on the device to the "out" port. Basically, an automated circuit breaker, like so:

<PC USB1>-------|  <relay> |
<PC USB2>-------|----/-----|<USB OUT> 

Does such a thing exist? Or should I start learning Arduino and make one?

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up vote 3 down vote accepted

Using the V-USB Software Stack for an AVR microcontroller, you can build one fairly easily with the included PowerSwitch project (schematics and program included).

Alternatively, you can create your own with an Arduino by using your PC's serial connection and a custom application to send the appropriate signals. I believe you can also use the PowerSwitch code with an Arduino, as they use Atmel microcontrollers. However, note that building your own circuit with the included schematic in PowerSwitch will likely be cheaper than an Arduino.

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