How to build an RS232 to RS485 Converter?


Do you want to learn how to convert RS-232 signaling to RS-485 signaling?

RS-232 is a widely used interface. One example is the serial port (COM port) of a PC. One drawback is that it can only support short distance communication (up to 50 ft). Some industrial applications need to extend the distance with robust communication. Converting RS-232 to RS-485 is one of the options, since RS-485 is widely used in industrial applications for long distance transmission.

Here is a reference design that implements the conversion circuit via an RS-232 transceiver, an RS-485 transceiver, a digital isolator, and a multivibrator. The industrial-level ESD protection is also included.

Reference Design for RS232 to RS485 Converter


This reference design provides a circuit of converting RS-232 signaling to RS-485 signaling. This allows for long-distance communication since the range supported by RS-232 is normally less than 50 feet while the range for RS-485’s can exceed 1000 feet. The design implements bidirectional half-duplex communication without any software interference.


  • Convert RS-232 to RS-485 signaling for bidirectional half-duplex communication without any software interference with hot plug-in feature
  • Low voltage design. The design works with both 3.3-V and 5-V supply
  • Industrial-level ESD protection
    RS-232 port: IEC 61000-4-2, ±8 kV contact, ±15 kV air
    RS-485 port: IEC 61000-4-2, ±30 kV contact, ±30 kV air; EFT, IEC 61000-4-4, 50 A; Surge, IEC 61000-4-5, 19 A;    Isolation: 5000 Vrms isolation protection
  • Extend system topology from point-to-point to multi-drop
  • Cable length up to 1000 ft


  • Point of sale
  • Factory automation
  • IP network cameras

Click here for the reference design. For a basic tutorial on RS-485, click here.



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