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QT Modbus Master Slave Example Issue



  • Hi,
    I am running the QT Modbus Master \ Slave example using comm ports but the Master is Timing out and not getting a response. However with the Category Logging running I can see the Slave does appear to be responding. The Client and Server output is below:

    Client
    qt.modbus: (RTU client) Sent Serial PDU: 0x0300000001
    qt.modbus.lowlevel: (RTU client) Sent Serial ADU: 0x110300000001869a
    qt.modbus: (RTU client) Send successful: 0x0300000001
    qt.modbus: (RTU client) Receive timeout: 0x0300000001
    qt.modbus: (RTU client) Sent Serial PDU: 0x0300000001
    qt.modbus.lowlevel: (RTU client) Sent Serial ADU: 0x110300000001869a
    qt.modbus: (RTU client) Send successful: 0x0300000001
    qt.modbus: (RTU client) Receive timeout: 0x0300000001
    qt.modbus: (RTU client) Sent Serial PDU: 0x0300000001
    qt.modbus.lowlevel: (RTU client) Sent Serial ADU: 0x110300000001869a
    qt.modbus: (RTU client) Send successful: 0x0300000001
    qt.modbus: (RTU client) Receive timeout: 0x0300000001
    qt.modbus: (RTU client) Sent Serial PDU: 0x0300000001
    qt.modbus.lowlevel: (RTU client) Sent Serial ADU: 0x110300000001869a
    qt.modbus: (RTU client) Send successful: 0x0300000001
    qt.modbus: (RTU client) Receive timeout: 0x0300000001

    Server
    qt.modbus.lowlevel: (RTU server) Received ADU: "110300000001869a"
    qt.modbus: (RTU server) Request PDU: 0x0300000001
    qt.modbus: (RTU server) Response PDU: 0x03020111
    qt.modbus.lowlevel: (RTU server) Received ADU: "110300000001869a"
    qt.modbus: (RTU server) Request PDU: 0x0300000001
    qt.modbus: (RTU server) Response PDU: 0x03020111
    qt.modbus.lowlevel: (RTU server) Received ADU: "110300000001869a"
    qt.modbus: (RTU server) Request PDU: 0x0300000001
    qt.modbus: (RTU server) Response PDU: 0x03020111
    qt.modbus.lowlevel: (RTU server) Received ADU: "110300000001869a"
    qt.modbus: (RTU server) Request PDU: 0x0300000001
    qt.modbus: (RTU server) Response PDU: 0x03020111

    I am using QT 5.14.1 (MSVC 2017 32 bit) on Windows 10 x64, and I am connecting the Master and Slave using Virtual Serial Port Driver 9.0 by Eltima Software, which shows me the byte count incrementing at the comm ports going from Master to Slave but not coming the other way.

    I tried using the TCP option instead of comm ports and TCP does work.

    Going back to comm ports I tried using a third party Modbus Slave Simulator and that QT Modbus Master example received data from that ok.

    Below is an image of the settings I am using.

    Any ideas what the issue may be ?

    alt text


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