RailControl only supports HSI-88-RS232. The USB version is not supported.
To configure a HSI-88 there has to be selected the serial port.
Especially under Linux one should consider the page RS-232 to USB converter.
There also has to be configured the number of S88 feedback modules, that are connected to a HSI-88. At most there can be connected 62 modules with 8 input pins. Modules with 16 input pins have to be configured as two modules.