Successfully connecting to the USB->Serial device, not yet confirmed working with Adaptronic.
Removed extraneous code from SerialUsbConnectedThread class. derives from UsbConnectedThread, uses most of the code from it.
Refactored code, created UsbConnector classes which do the connection initialisation, leaving a UsbDeviceConnection that can be used to communicate with the Adaptronic.
Re-add code requesting Intent for Serial to USB device.
Not entirely sure this is the right way to do it, it seemed to work, but I did get the popup a couple of times asking if I wanted to grant the permission.