A simple converter can be sourced online, but the only thing he could find locally that was even close was a USB to RS-232 converter. He used that component to craft his own USB to RS-485 bridge.

The DB9 is connected in parallel with the 'COM0' port header ... Please note that this module is designed to connect to 'real' RS232 hardware, not to an emulated, USB-based RS232 adapter. It may work ...

The Universal Serial Adapter is an open-source hardware project designed to bridge USB-C, RS232, and TTL communication. This fully assembled adapter is packed with features tailored for advanced ...