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Modbus TCP/RTU

  • Checklist to debug your Modbus RTU Network

    This articles explains how to debug your Modbus RTU network.

     

    First of all, please collect the required information for each Modbus RTU device, including the bus speed, parity bit, and stop bit.

    It's possible to create a maximum of two networks by following the article How to connect a Modbus RTU device, each grouping equipment with the same communication configuration and assign them to the two RS485 ports of the box. If the characteristics of the equipment require the setup of more than two homogeneous networks, it is necessary to order another box.

    Here is the important checklist to follow if you are experiencing trouble connecting Modbus RTU equipment in your Tower or Bridge.

     

    HARDWARE CHECK :

    1. Please check the connections between Wattsense's device and the Modbus RTU equipment.
    2. Check the LED status, which should include a heartbeat and RS485 LED.                           
    3. Ensure that the box is correctly powered with a 24V DC power supply, with a tolerance of +/-10%, and a minimum current rating of 2A.
    4. If the manufacturer's instructions recommend it, connect a 120-ohm resistance between A+ and B+.

    NETWORK CHECK :

    1. Do not group together devices with different communication parameters on the same Bus.
    2. Serial wire the network or each of the two networks

    CONFIGURATION CHECK :

    1. Configure the address of the 1st Modbus slave to 1, the 2nd to 2, the 3rd to 3 and so on
    2. A network MUST NOT contain multiple slaves with the same address
    3. Write down the network to which the equipment is connected as well as its address, brand, and model of the equipment and any identifying information.
    4. Check if the register table is correctly matching the properties configuration in the user console.

    For more details about Modbus RTU installation the Wattsense's Installation Guide  

    Wattsense has over 100 pre-configured Modbus RTU devices. If your device is not available, please let us know, and we will add it for free: Request for a new Equipment

    In case the register table is not matching the properties configuration, please contact us: Wattsense Support

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  • Requirements to connect a ModbusTCP/RTU equipment to the Box

     

    This article is about the requirements to connect a ModbusTCP/RTU equipment to the Tower/Bridge.

     

    Modbus IP RTU
    Slave address* of all equipment If applicable R
    IP address of all equipment R N/A
    Modbus register list* (so-called exchange table) of all equipment R R
    Modbus UDP ports R N/A
    Network communication configuration (Baud rate/Parity/Data bit/Stop bit) N/A R
    R = Required/O = Optional / N/A = Not Applicable

     

    Here is the parameters that you'll need to fill in order to create your modbus Equipment :

    Modbus IP

    In an IP network you'll have to be aware of your IP parameters :
     
    Be sure that your choosen IP address is available and free on your IP network.
    Be sure that the Box can access the targeted equipment (Both are in the same subnetwork or accessible using a gateway for example)
     
    Article.RequirementsToConnectAModbusTCPRTU.IPParameters.png
     
    Slave address in Modbus IP is not mandatory. There are some Modbus TCP/IP <==> Modbus RTU gateway that forward Modbus packet to a slave. That’s why the slave address needs to be known. 

     

    PointDexclamationSmall.png If you have a VPN on this network be sure that the Tower/Bridge is whitelisted otherwise the VPN will block Tower/Bridge communication.
     

    Modbus RTU :

    In a serial network be sure that the chosen address (slaveID) is free and available on the network.
    Be sure that you are using a twisted paired communication cable.
    Article.RequirementsToConnectAModbusTCPRTU.RTUParameters.png
    PointDexclamationSmall.png Please find here the hardware information

     

     

    Modbus properties requirements

    In order to get your data correctly, you'll have to know the Modbus register table of the device.
    In this document (provide usually by the manufacturer) you'll have the information to fill these following blanks.
     
    Article.RequirementsToConnectAModbusTCPRTU.Properties.png

     A list of the point to be read can be provided instead of the entire Modbus register list and the following points are required

        • Name of the variable
        • Register address
        • Data format
        • Access type
        • Modbus function used

    If you encounter a problem, do not hesitate to contact us: Wattsense Support

     

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  • Checklist to debug your ModbusIP Network
    This article describes the checklist to debug your ModbusIP Network.
    Here is the important checklist to follow if you have trouble to connect modbus equipment :
     

    HARDWARE CHECK :

    1. Check that the ethernet cable is correctly plug at both side (Box and equipment).
    2. Check that the box is correctly power with a 24V DC +/-10%, 2A power supply.
    3. Led statuts : Heartbeat blinking and if the GSM is use that the led is blinking.

    NETWORK CHECK :

    1. Be sure that the box is in the same network as your equipment.
    2. Be sure that there is no firewall blocking the Tower/Bridge traffic.
    3. Check the IP network parameters if there is no DHCP server.
      1. Gateway IP address
      2. Netmask
    4. Try to ping the Modbus equipment with a laptop if possible.

    CONFIGURATION CHECK :

    1. Check the slave address of the equipment.
    2. Check if the register table is correctly matching the properties configuration in the user console.
    3. Check if you are using the correct modbus function for read and write.
    4. If you are getting wrong data please try to modify the Data format 

     

    TEST WITH AN OTHER MODBUS CLIENT (MODBUS DOCTOR) :

    1. If you cannot access the equipment with your Wattsense product, try with an other Modbus client.

     

    PointDexclamationSmall.png Aim of this test: Be sure that your modbus equipment is available and correctly configured in the modbus network. Check also if an other device (your laptop) can connect to it if the box cannot.
    If you can connect to the equipment after this test :
    - The targetted modbus equipment is accessible in the modbus network.
    - The issue would be:
    •            The Box network is not correctly setup
    •           The Box has an issue. Please contact us : support.wattsense.com

     

    First of all you will need to download the Software: Modbus Doctor
     
    Once it's done, check that you can ping the Modbus Equipment with your Laptop :
      NO PING : You need to check again your network settings

      PING : You can go ahead

     
    -> Launch Modbus Doctor
    mceclip0.png
    1. Click on the "Settings" tab and setup the IP address of the targeted Modbus device.
    2. Be sure that the port is the same of the equipment (most of the time it's 502)
    3. Close the tab
    mceclip2.png
     
    1. Configure the Slave ID number of the targeted equipment. You will find it in the equipment configuration itself.
    2. Click on the "Connection" Button
         -> If you have the "Status: Connected" that means your network setup is OK.
         -> If not you should double check the modbus configuration.
    3. In order to read the properties you can setup the Register
    4. Click on READING.
     
    If you cannot connect to the equipment also that means either:
    1. Your equipment is in default.
    2. Your network setup is wrong.
    If you can connect to the equipment correctly with your laptop that means the Box should be able to.
    ​
    If you have any problem, please do not hesitate to contact us: Wattsense Support
     
     
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