Modbus RTU with MAX 485 ?

Runtime 🇬🇧
Kampfwurst
2015-01-08
2015-01-09

  • Kampfwurst - 2015-01-08

    Hello

    I have a "big" Problem.
    I would like to use the MAX485 for Modbus RTU on the UART Port (GPIO14 and 15). Everything is fine but for the MAX485 I need to change the direction (transmit or receive) with a pin.
    If this GPIO pin is high i can send through the MAX485. If this GPIO Pin is low than the MAX485 can receive.

    Now i have the Problem that can´t get any direction variable from the Modbus library to toggle this Pin so im stuck at the moment.

    Has someone maybe any idea

    Greetings Christoph

     

  • eschwellinger

    eschwellinger - 2015-01-08

    Hello Christoph,

    I'm not really sure, but using MAX 485 on the tty is not really possible without having
    handshake pins to give the direction. To workaround this by a kind of own implemented mechanism
    will not lead to a reliable solution.
    I would recommend to use a ready to use USB to RS485 Adapter instead implement this with a huge effort.

    Maybe I am totally wrong and someone could give us a hint how to solve this with a MAX485 circuit.

    Best Regards
    Edwin

     

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