RS485A (IMX8)
=============

.. admonition:: Galvanic Isolation

    The RS485A interface is **galvanically isolated** to prevent ground-loops and increases overall system resilience.

RS485A 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
     - RS485A A
     - Non inverting RS485A differential signal
   * - 3
     - RS485A B
     - Inverting RS485A differential signal
   * - 4
     - RS485A 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 RS485A ground has an high impedance connection to the isolated ground of the isolated RS485 transceiver.

.. image:: rs485a-bin.png
      :align: center
      :scale: 40%

Preconfigured Docker Container
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

There are `preconfigured <https://github.com/pika-spark/pika-spark-containers>`_ Docker containers (``rs485a-minicom``, ``rs485a-libdynamixelplusplus``) demonstrating how to access RS485A.

.. code:: bash

    git clone https://github.com/pika-spark/pika-spark-containers
    cd pika-spark-containers/rs485a-minicom
    ./docker-build.sh
    sudo ./docker-run.sh [baudrate]

Manual Configuration
^^^^^^^^^^^^^^^^^^^^

Configure and use RS485A using ``minicom``:

* Download the `Alpine Docker <https://hub.docker.com/_/alpine/>`_ image and install ``minicom``:

.. code:: bash

    docker pull alpine:latest
    docker run -it -u 0 --device /dev/ttymxc1 alpine:latest sh
    apk add minicom
    minicom -D /dev/ttymxc1 -b 115200

* Configure ``minicom`` for RS485 / No Flow-Control (Ctrl+A, O)

.. code:: bash

    H -     RS485 Enable      : Yes
    I -   RS485 Rts On Send   : Yes

.. image:: rs485a-minicom.png
      :align: center