I'm looking for a way to be able to electrically switch between 4-wire and 2-wire RS-485. Up until now I have used jumper connections to establish both communication ways with one circuit. But I would like to be able to switch electronically (from a MCU). An option would for example be a relay, but I don't have the power capabilities for this. Does any of you know of any known circuits that deal with this issue. A figure to describe this issue:

enter image description here

  • \$\begingroup\$ What will implement data flow-control? \$\endgroup\$
    – Andy aka
    Commented Jan 16, 2023 at 10:09
  • 1
    \$\begingroup\$ The THVD1424 has this built in. \$\endgroup\$
    – CL.
    Commented Jan 16, 2023 at 11:28
  • \$\begingroup\$ Thanks the THVD1424 was exactly what I was looking for \$\endgroup\$
    – luukito
    Commented Jan 16, 2023 at 12:49

1 Answer 1


if you use a "2 wire" RS485 drivers you just need to gate the enable signal.


simulate this circuit – Schematic created using CircuitLab


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