Low-cost USB to UART bridge. Found on Arduino clone boards, needs CH340 driver.

I2C 8-bit I/O expander. Adds 8 GPIO pins over I2C, used in LCD I2C backpacks.

16-bit I2C I/O expander. 8 devices per bus, interrupt support, configurable pull-ups.

RS-232 to TTL level converter. Interfaces microcontrollers with serial COM ports.

USB to UART bridge IC. Creates virtual COM port, no external components needed.