This is not a software problem. EIA-485, EIA-232, and USB are all serial interfaces. At the software side you usually have a COM port. Accessing the port will not differ for a specific device. There are two options to reduce the amount of external hardware:
- Use an EIA-485 interface card
- Use an EIA-485 to USB converter
Both should come with drivers that install a new COM port (like the one of your 'brain box' which is an EIA-232 to USB converter). There should be no software changings necessary when opening the new COM port.