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  • I'm getting this data source alarm: 'COM1': Exception from modbus master: invalid message start: 48

    I've a, ASCII serial modbus device (builted by us). I've used a serial port sniffer and the received data is correct. If I change the device for a software simulator, the error does not happen.


  • Can you send the message traces? I'll try them here.


  • Do you mean the output from the mango termianl?


  • No. You said to used a serial port sniffer. That's the data i'd need.


  • These are the messages of the sniffer:

    Mango query -> :010100000002FC\r\n
    Device response -> :01010101FC\r\n

    Mango query -> :010300000008F4\r\n
    Device response -> :010310009100000000000000000000000000005B\r\n

    Can be overwriting the receive FIFO? Can you add the message received with errors in the log of mango?
    Thanks


  • Well, there's nothing wrong with the messages. Where does the error occur? On every req/res, or just specific ones?


  • This type of error is presented from time to time. As we add records errors become more frequent.
    This is more complex to determine. When using a simulator of a slave on the same PC and with the same records (simulating a serial port), it works perfectly.
    That is why I consult if there is a possibility that the serial FIFO is overwritten.
    To better identify the problem, it is necessary that this system log message that gives the error received.
    The only test that would do is make the simulator work on another PC and the serial port with handshake and without it.


  • Have you tried setting the concurrency level to "transport"?


  • When Mango can not interpret the message retry the query. In any of the answers, Mango able to interpret the message and takes it as valid. The problem is that ALL answers are the same but the system fails despite that.