Open Hardware USB to RS485 Adapter

RS485 Adapter - Perspective

While developing the Luma RS485-networked LED driver we discovered a need for a small and inexpensive USB to RS485 adapter. We designed an adapter with a FTDI basic UART chip (FT230XS) and an inexpensive TI differential receiver (SN75176). Our small selection of parts brings the cost down to just over $5 for one adapter.

RS485 Adapter - Front

The adapter has a mini USB port and a surface-mount 8P8C (RJ45) jack. Two LEDs (RX and TX) are located on the left of the USB port, and a white power LED is located on the left of the RJ45 jack.

RS485 Adapter - Side view with cables attached

The RJ45 jack is DMX-compliant, and the solder-jumpers shown on the right of the RJ45 jack optionally connect pins 4 and 5 to +5v. Connecting these jumpers breaks DMX compliance, but allows you to power your custom projects from the bus. The transmit and receive enable lines on the differential transceiver are connected to the CBUS pins of the FTDI chip, allowing the FTDI chip to control transmit and receive enable automatically. The functionality of these pins is configurable with the FT-PROG utility. A sample configuration XML file is included in the sources below.


Ethan is a computer engineer and open source hardware/software developer from Michigan. He enjoys AVR and linux development, photography, mountain biking, and drinking significant amounts of home-roasted coffee. Find out more at

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2 comments on “Open Hardware USB to RS485 Adapter
  1. Brett Burton says:

    Hi. Would this board allow me to use power over internet from the ethernet connection to something running off the mini usb connection? It seems like it’s designed to work the opposite direction (usb to ethernet), but I thought I’d check.

  2. stavros says:

    Good day i am cctv installer in Athens Greece
    i have to connect
    a HIKVISION DVR DS-7216HQHIK1 with USB input for keypad
    a HIKVISION DS 1003KI KEYPAD CONTROLLER with RS485 Half-duplex
    Baud Rate : 12~19200bps

    what module converter do you recoment ?

    what cost and how soon you ship out .

2 Pings/Trackbacks for "Open Hardware USB to RS485 Adapter"
  1. […] Use ethernet cables to connect components of a project and send I/O signals or serial communications between nodes, adding extensibility and modularity to any design. This breakout board would also work well in conjunction with our USB to RS485 Adapter. […]

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