Simulation tools have developped to the system level for many years. Actually system level simulators are powerful enough to communicate with external world via TCP/IP and many native interfaces (RS232, Bluetooth, USB).

RS232 port has disappeared from PCs, replaced by USB interface. So, we need to migrate from RS232 to USB and, to simplify this migration, Usb-Uart Bridge Components can help us.

Every thing you need (schematics, libraries, pcb) to built a USB to RS232 converter is available on SparkFun web site.