I&#x27;ve used those SiLabs CP2102 USB to serial chips, but to get 45 baud for antique Teletype machines.  Using one to just get a second USB port is painful.<p>The Raspberry Pi Model B has two USB ports, and they&#x27;re &quot;on the go&quot; ports, so you can set one as master and one as slave. So that should be usable as a general purpose USB MITM device.