Here's a simplified example schematic for an Icom CI-V USB interface:

Below is the classic, reliable design used in most DIY and commercial CI-V USB adapters. It uses a (like CP2102, CH340G, or FT232RL) plus an opto-isolated buffer .

: If your radio’s CI-V port provides +5V on the ring, use that for the pull-up. It keeps the interface completely passive on the radio side.