USB to serial adapters on a PCB — drivers and logic levels.
Bridge ICs connect a USB port to asynchronous serial. Match I/O voltage to the MCU (3.3 V vs 5 V tolerant). Check driver availability on Windows, macOS, and Linux before you pick a chip.
PCB notes
Route USB D+/D− as a controlled pair per the MCU or bridge datasheet. Place a decoupling capacitor at VCC and respect crystal or clock requirements if the part needs an external load cap.
Widely used examples
Examples for orientation only. Not an offer, stock list, or complete parametric search.
Manufacturer
MPN
Notes
FTDI
FT232RL
USB full-speed UART, SSOP
Silicon Labs
CP2102N-A02-GQFN28
USB to UART, 3.3 V I/O
WCH
CH340C
Low-cost USB serial (verify driver support on target OS)