USB to Multi-Protocol Serial Cable - RS-232 / TTL UART / RS-485

This USB to Multi-Protocol Serial adapter cable supports RS232 serial, TTL UART serial, RS485 and RS422. All with quick-connecting screw terminals so you don't need to do any soldering or use special cables.

Inside is a FTDI FT231 USB to serial converter - this chip uses 5V logic and provides the UART serial signals that are converted into the different formats. Supported signal rates are 300 baud to 3 Mbaud. FTDI drivers are built into just about every OS these days - but if you need to install, there's free VCP drivers

For the RS-232 signal side, theres a UM213 signal level converter with +-8V logic level I/O. All eight (5/3) RS-232 signals are exposed. The RS-232 converter can handle up to 250kbps.

For the UART signal side, it is connected directly to the FT231. Logic level is 5V, and only RX/TX and 5V/3V/GND are exposed.

For RS-485/RS-422 signal side, the UART RX/TX lines are connected to MAX485 chips. 

More information is available on the website of Adafruit.