There are two stages, one which converts RS-232 to TTL, and the other converts TTL to USB. [André] removed the RS-232 chip and patched his own board (shown on the left) into its TTL lines.

USB to TTL (FTDI), and null modem/rollover adapters. The adapter circuit in this repo carries an inexpensive CPL2102 USB breakout board, cheap and plentiful on eBay, and exposes configurable ports for ...

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 ...