Modbus RTU comunication issue

Forum Home Forums Communicating with Devices Modbus Modbus RTU comunication issue

Viewing 15 posts - 1 through 15 (of 16 total)
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  • #5565
    Avatarcooldjmc
    Participant

    Hi, i’m getting a comunication issue in Comunicator after some modbus rquests that are workink ok, i get this error messages:

    2019-06-17 17:00:09 Communication session with the Device 4 “Compresor 4”, type: KpModbus, call number: 4
    Request element group “Comp-DATA”
    Send (8): 04 03 00 00 00 5D 84 66
    Receive (5/5): 04 03 BA 00 00
    Receive (186/186): 00 5C 00 01 00 01 00 00 00 00 00 00 00 00 00 00 00 00 00 01 00 01 00 01 00 01 00 01 00 00 00 00 00 00 00 00 00 00 00 28 00 24 00 1F 00 00 01 87 00 00 00 0C 00 04 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 15 00 12 00 02 00 08 00 28 00 2C 00 25 00 10 00 00 00 00 00 00 00 00 00 00 00 00 00 00 02 E2 01 4B 00 00 00 05 00 00 00 00 02 03 02 03 00 00 00 00 00 00 00 39 00 00 00 00 00 00 00 00 00 00 00 4B 00 00 00 00 00 00 00 00 00 00 00 17 00 00 00 00 13 70
    OK!

    2019-06-17 17:00:10 Communication session with the Device 4 “Compresor 4”, type: KpModbus, call number: 4
    Request element group “Comp-DATA”
    Send (8): 04 03 00 00 00 5D 84 66
    Receive (5/5): 04 03 BA 00 00
    Receive (186/186): 00 5C 00 01 00 01 00 00 3F 3F 00 00 00 01 02 00 00 00 00 00 00 01 00 01 00 01 00 3F 3F 3F 3F 01 00 01 00 00 00 00 00 00 00 00 00 01 00 28 00 24 00 1F 00 00 01 87 00 00 00 0C 00 03 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 3F 3F 00 00 00 00 00 00 01 02 04 08 00 00 00 00 00 00 00 80 00 00 00 00 00 00 00 15 00 12 00 02 00 08 00 28 00 2C 00 25 00 10 00 00 00 00 00 00 00 00 00 00 00 00 00 00 02 E2 01 4B 00 00 00 05 00 00 00 00 02 03 02 03 00 00 00 00 00 00 3F 3F 00 39 00 00 00 00 00 00 00 00 00 08 00 4B 00 00 00 00 00 00 00 00
    CRC error!
    Request element group “Comp-DATA”
    Send (8): 04 03 00 00 00 5D 84 66
    Receive (0/5):
    Communication error!
    Request element group “Comp-DATA”
    Send (8): 04 03 00 00 00 5D 84 66
    Receive (0/5):
    Communication error!

    2019-06-17 17:00:14 Communication session with the Device 4 “Compresor 4”, type: KpModbus, call number: 4
    Request element group “Comp-DATA”
    Send (8): 04 03 00 00 00 5D 84 66
    Receive (0/5):
    Communication error!
    Request element group “Comp-DATA”
    Send (8): 04 03 00 00 00 5D 84 66
    Receive (5/5): 04 3F 3F 03 BA
    Incorrect PDU function code
    Request element group “Comp-DATA”
    Send (8): 04 03 00 00 00 5D 84 66
    Receive (0/5):
    Communication error!

    2019-06-17 17:00:18 Communication session with the Device 4 “Compresor 4”, type: KpModbus, call number: 4
    Request element group “Comp-DATA”
    Send (8): 04 03 00 00 00 5D 84 66
    Receive (0/5):
    Communication error!
    Request element group “Comp-DATA”
    Send (8): 04 03 00 00 00 5D 84 66
    Receive (0/5):
    Communication error!
    Request element group “Comp-DATA”
    Send (8): 04 03 00 00 00 5D 84 66
    Receive (0/5):
    Communication error!

    2019-06-17 17:00:23 Communication session with the Device 4 “Compresor 4”, type: KpModbus, call number: 4
    Request element group “Comp-DATA”
    2019-06-17 17:00:23 Error communicating with Device 4 “Compresor 4”: Error writing data: Uno de los dispositivos conectados al sistema no funciona.

    2019-06-17 17:00:23 Close serial port COM4

    2019-06-17 17:00:23 Open serial port COM4
    2019-06-17 17:00:23 Error executing the communication channel actions before session with a device: Error opening serial port: Access to the port ‘COM4’ is denied.

    2019-06-17 17:00:23 Unable to communicate with Device 4 “Compresor 4” because connection is not established

    2019-06-17 17:00:24 Open serial port COM4
    2019-06-17 17:00:24 Error executing the communication channel actions before session with a device: Attempt to open serial port can not be earlier than 5 seconds after the previous.

    2019-06-17 17:00:24 Unable to communicate with Device 4 “Compresor 4” because connection is not established

    2019-06-17 17:00:24 Open serial port COM4
    2019-06-17 17:00:24 Error executing the communication channel actions before session with a device: Attempt to open serial port can not be earlier than 5 seconds after the previous.

    2019-06-17 17:00:24 Unable to communicate with Device 4 “Compresor 4” because connection is not established

    2019-06-17 17:00:24 Open serial port COM4
    2019-06-17 17:00:24 Error executing the communication channel actions before session with a device: Attempt to open serial port can not be earlier than 5 seconds after the previous.

    #5567
    MikhailMikhail
    Moderator

    Hi,

    How the devices are physically connected to Rapid SCADA server?

    #5569
    Avatarcooldjmc
    Participant

    Hi, are conected with USB to Rs485 converters, there are 2, each one conected to a USB port on the mainboard. Each converter pulls 2 RTU Slaves. But the test i made is only with one slave active.

    #5575
    MikhailMikhail
    Moderator

    The log says that there are problems with a converter:

    2019-06-17 17:00:23 Open serial port COM4
    2019-06-17 17:00:23 Error executing the communication channel actions before session with a device: Error opening serial port: Access to the port ‘COM4’ is denied.

    #5576
    MikhailMikhail
    Moderator

    May be other application uses the same port COM4.

    #5582
    Avatarcooldjmc
    Participant

    Thank you for your answers. what i don’t understand is after this:
    2019-06-17 17:00:23 Communication session with the Device 4 “Compresor 4”, type: KpModbus, call number: 4
    Request element group “Comp-DATA”
    2019-06-17 17:00:23 Error communicating with Device 4 “Compresor 4”: Error writing data: Uno de los dispositivos conectados al sistema no funciona.

    2019-06-17 17:00:23 Close serial port COM4

    the COM port remains blocked and no other app can open it, also if i try restart the computer it won’t restart remains on “Shutting down windows ” screen and i must reset it.

    #5585
    MikhailMikhail
    Moderator

    Seems like hardware problem. What USB-COM converter do you use?

    #7197
    Avatarhethongscada62
    Participant

    Dear Mr. Mikhail.
    I am creating a new project “Smart ScadaFarm” on Raspberry Pi4. It is running but not unstable. Maybe all my devices are connecting to RaspberryPi4-server via Rs485-WiFi converter. Is that the cause of instability?.
    Now i want that all these devices will be connected to Raspberry Pi4 via RS485-USB converter. Can they connect to Pi4? How will i configure?
    Thanks and best regards

    #7199
    MikhailMikhail
    Moderator

    Hello,

    Is that the cause of instability?

    You should provide communication logs to check.

    Can they connect to Pi4?

    Depends on the converter. I can’t suggest a particular. As I know, many of them work with RPi.

    #7316
    Avatarkumajaya
    Participant

    I recently have a bad experience with Moxa NPort device for transmit Modbus RTU over ethernet in RFC2217 mode. I have to compile Moxa Real COM driver for a stable communication. Working flawlessly after.

    #7325
    MikhailMikhail
    Moderator

    Using Moxa NPort, I prefer TCP server or TCP client mode.

    #7905
    Avatarkumajaya
    Participant

    @Mikhail Today I realized how simple NPort in TCP mode. Thank you.

    Not actually NPort device I use here but a GSM modem from Moxa with a serial port. With a private IP from GSM operator, the only option to access it is via OnCell Central Manager. OCM map the serial port to a local TCP port.

    #7908
    MikhailMikhail
    Moderator

    If you use GSM modems, you can try a mode when Communicator is TCP server, and a modem is TCP client, so a modem doesn’t need static IP address.

    #7923
    Avatarkumajaya
    Participant

    I’ll try it @Mikhail. For now I accessed it from Node-RED using node-red-contrib-modbus. I have to enable TCP in telnet mode because got incorrect Modbus stream in default TCP mode.

    #8369
    AvatarSGG
    Participant

    Hello Mikhail and team,
    I have rapid scada connected to 6 modbus devices through rs485…they all worked and communicated effectively at first…2 days later, I observed that only the terminal (at the end of the daisy chain) device is communicating. When I turn off that device, it picks the next terminal device and communicates with it properly…I later changed the “number of request retries on error” in the communication parameter from the default 3 to 20 and all the device started communicating. I observed that for some devices, it takes about 14 retries before a response is sent by the device.

    I dont know what might be caussing this, although, I suspect I need to insert a terminating resistor of 120ohms…kindly help me with any suggestion from experience.

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