Simple USB to RS232 (Serial) Converter Schematic Diagram

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The following circuit is quite simple. It needs only few components to complete a working converter. This serial RS232 to USB adapter might be the only help for old personal computers that only provides RS232/COM Port since many new computers nowadays only provide USB ports. This serial adapter uses FT232 USB-RS232 chip from FTDI (Future Technology Devices International).

There are so many applications can be built based on FT232 chip. Namely USB-USB data transfer cables, USB intrumentations, USB – RS232 converters/cables, USB-PDA interface cables, USB digital cameras, USB-RS422 / RS485 High Speed Industrial Links, USB-Serial Bar Code Readers, USB-USB null-modem cables, USB-56k/V90 modems, USB ISDN and ADSL modems, Ultra-high performance Serial port for legacy-free PC system boards/Easy PC’s, USB interface for MP3 Players, and many more.

usb-rs232 converter circuit diagram

usb-rs232 converter circuit diagram

The main features of FT232 USB-RS232 FTDI Chip are as follows :

  • Support for Event Characters and Line Break condition
  • Auto Transmit Buffer control for RS485
  • UHCI / OHCI Compliant
  • Compact 32 pin  ( 7mm x 7mm ) MQFP package
  • Integrated 6MHz – 48MHz Clock Multiplier aids  FCC and CE compliance
  • USB 1.1 Specification Compliant
  • Integrated 3.3v Regulator – No External Regulator Required
  • 4.4v .. 5.25v Single Supply Operation
  • Single Chip Multi-Function Data Transfer Solution
  • RS422/RS485 Link to 2000K baud
  • USB VID, PID, Serial Number and Product Description Strings in external E2PROM.
  • 384 byte receive buffer / 128 byte transmit buffer for high data throughput
  • Full hardware assisted or X-On/X-Off handshaking
  • RS232 link from 300 baud to 920K baud

For more details about the datasheet and application notes, go to the FTDI website : (

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