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USB 4-Port Serial Adapter - USB 2.0 to DB-9 Port RS232 with FTDI CHIP - Coolgear
3 in 1 USB TO RS232 TTL232 Pro Mini Download cable Serial ports CH340 Converter Board Industrial grade IC SP232 [UD67A01] - USD $4.99 : canton-electronics.com
FT232 USB UART Board (Type A) FT232R FT232RL to RS232 RS485 TTL Serial Converter Module Kit @XYGStudy : Electronics
FT232 USB UART Board (Type A) FT232R to RS232 Serial Converter Module Kit 700646948000 | eBay
3 IN 1 Pro Mini USB to RS232 Converter Module PC COM Bus Board for Arduino AVR | eBay
SparkFun USB UART Serial Breakout - CY7C65213 - BOB-13830 - SparkFun Electronics
SparkFun USB to Serial Breakout - FT232RL - BOB-12731 - SparkFun Electronics
Amazon.com: WITMOTION USB-UART 6-in-1 USB to Serial Converter, Multifunctional (USB to TTL/RS485/232, TTL-RS232/485, 232 to 485), Universal Adapter Module with CP2102 Compatible with Windows 7/8/10,Linux, Arduino : Electronics
Pl2303 Geninue Chipset Usb Rs232 Serial Adapter Converter Board Pcb Module - Pc Hardware Cables & Adapters - AliExpress
Ftdi Usb Rs232 Serial Converter Module Usb Plug Adapter Board Ftdi Usb Pcb Serial Converter Module Connector Support Win10 - Pc Hardware Cables & Adapters - AliExpress
PL2303 USB rs232 converter adpater serial module port Prolific pl2303 rs232 pcb board adapter|Computer Cables & Connectors| - AliExpress
Debug Board USB to RS232 Isolated Serial Converter from DUPPA on Tindie
USB 16 Channel Relay Module - RS232 Controlled
Serial (USB, Ethernet, CAN, RS232/485) Tower System Module | NXP Semiconductors
RS232/USB To LIN Bus Monitoring Module
Amazon.com: USB to I2C USB to RS232 USB to Serial USB Converter Module Adapter Board : Electronics