RS485B (STM32H747)
==================

.. admonition:: Galvanic Isolation

    The RS485B interface is **galvanically isolated** to prevent ground-loops and increases overall system resilience.

RS485B Pin-out
^^^^^^^^^^^^^^

Connector-type: **SM04B-GHS-TB** (4-pin, 1.25 mm) (`Datasheet <https://www.jst-mfg.com/product/pdf/eng/eGH.pdf>`_)

.. list-table::
   :widths: 10 25 65
   :header-rows: 1

   * - Pin
     - Name
     - Description
   * - 1
     - N.C.
     - Not connected
   * - 2
     - RS485B A
     - Non inverting RS485B differential signal
   * - 3
     - RS485B B
     - Inverting RS485B differential signal
   * - 4
     - RS485B GND
     - GND connection to other RS485 nodes¹

¹ Although RS485 is a differential bus in nature the common mode voltage on the differential bus signals can theoretically exceed the maximum common mode voltage acceptable to the signal and power isolated RS485 transceiver. In order minimize large differences in ground potentials across all nodes RS485B ground has an high impedance connection to the isolated ground of the isolated RS485 transceiver.

.. image:: rs485b-bin.png
      :align: center
      :scale: 40%