RS-485 Breakout

Replacement:BOB-09823. So we made a mistake. A and B are mislabeled. They should be swapped. Oops! This is your chance to take advantage of our mistake. If you don't mind working with a few swapped labels you can save some money with this sale board. If you need your labels correct, check out the new version that is corrected here. Also good for reference of how things should be. 

This is a breakout board for the SP3485 RS-485 transceiver IC, which will convert a UART serial stream to RS-485. The SP3485 is a half-duplex transceiver, so it can only communicate one way at a time, but it can reach transmission speeds of up to 10Mbps. This board requires a very low amount of power and can operate from a single +3.3VDC supply.

This breakout board includes the SP3485 RS-485 transceiver, filter capacitor, and other components shown on the schematic. We've broken out the RS-485 output to three different connections: (1) an RJ-45 connector, (2) a 3-pin 3.55mm screw terminal, and (3) a 3-pin 0.1" pitch header; none of these output connectors come populated.

  • Fully equipped with SP3485 RS-485 transceiver and supporting components
  • Operates from a single +3.3V supply
  • Interoperable with +5.0V logic
  • RS-485 input/output broken out to RJ-45 connector, 3.5mm screw terminal, and 0.1" pitch header
  • Driver/Receiver Enable connected to RTS line
  • -7V to +12V Common-Mode Input Voltage Range
  • Allows up to 32 transceivers on the serial bus
  • Driver Output Short-Circuit Protection
  • 0.9x1.0"


Looking for answers to technical questions?

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  • floris / about 13 years ago / 1

    anybody a good tutorial how to use these with an ardunio?

  • elmer_fud / about 13 years ago / 1

    Apparently it is somewhat common to reverse A and B. I have encountered this on some sensors and this quote from wikipedia says a lot.
    The EIA-485 signaling specification states that signal A is the inverting or '-' pin and signal B is the non-inverting or '+' pin.
    This is in conflict with the A/B naming used by a number of differential transceiver manufacturers, including, among others:
    * Texas Instruments, as seen in their application handbook on EIA-422/485 communications (A=non-inverting, B=inverting)
    * Intersil, as seen in their data sheet for the ISL4489 transceiver[6]
    * Maxim, as seen in their data sheet for the MAX483 transceiver[7]
    These manufacturers are incorrect, but their practice is in widespread use.
    Therefore, care must be taken when using A/B naming.
    If the 485 sensors are not working right try reversing the signal pins. It should not hurt anything because the A and B signals are differential and it will just flip the bit if they are backwards.

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