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Instructions to Connect a Modbus Device

This article introduces how to connect an end devices based on the Modbus protocol to DCE 5.0 Cloud Edge Collaboration and interact with the cloud. A simulated device is used as an example to introduce the overall implementation process.

The process to connect an end device is as follows:

graph TD
    A(Start) --> B(Connecting end devices to edge nodes)
    B --> C(Creating device models)
    C --> D(Creating end devices)
    D --> E(Deploying the Mapper device)
    E --> F(End)

classDef plain fill:#ddd,stroke:#fff,stroke-width:1px,color:#000;
classDef k8s fill:#326ce5,stroke:#fff,stroke-width:1px,color:#fff;
classDef cluster fill:#fff,stroke:#bbb,stroke-width:1px,color:#326ce5;

class A,F plain
class B,C,D,E cluster

click B "https://docs.daocloud.io/en/kant/best-practice/modbus-device-demo.html#connecting-end-devices-to-edge-nodes"
click C "https://docs.daocloud.io/en/kant/best-practice/modbus-device-demo.html#creating-device-models"
click D "https://docs.daocloud.io/en/kant/best-practice/modbus-device-demo.html#creating-terminal-devices"
click E "https://docs.daocloud.io/en/kant/best-practice/modbus-device-demo.html#deploying-the-device-mapper"

Preparation work

  • Simulated end device with the Modbus protocol: In this article, the end device is simulated as a deployment.

    Simulated device image: release-ci.daocloud.io/kant/modbusmock:v0.1.0

  • Mapper device: Developed based on the KubeEdge DMI framework, it can collect data for Modbus protocol devices. This device is only suitable for the simulated device mentioned above.

    Mapper image: release-ci.daocloud.io/kant/devicedemo:v1.1

  • Edge nodes: For node connect requirements, refer to Edge Node Connect Requirements

Connecting end devices to edge nodes

Since the Modbus device in this article is a simulated device, the simulated device image needs to be deployed to the edge node first to run and connect the simulated device. For the deployment process, refer to Creating Deployments.

The Advanced Settings includes the following parameters:

  • Node Scheduling: Select the node that the device needs to connect to.
  • Network Configuration: Choose the host network as the network type.

Creating device models

For the device model creation process, refer to Creating Device Models.

Please ensure the device model parameters are set as follows:

  • Access Protocol Name: modbus-tcp

  • Name , Type , and Access Mode in Twin Attributes should match the settings shown in the diagram below.

Creating end devices

  1. Fill in Basic Information and select the device model mentioned above.

  2. Fill in Device Settings , and the configuration of the twin attributes associated with the model is as follows:

    Access method for the temperature attribute:

    offset: 1  # Register offset
register: HoldingRegister  # Holding register

    Access method for the humidity attribute:

    offset: 1  # Register offset
register: InputRegister  # Input register

  3. Fill in Access Settings with the following parameters:

    address: 0.0.0.0:11502

  4. After the device is successfully created, it will automatically redirect to the device list. Click Bind Node on the right side of the list.

Deploying the Mapper device

The Mapper device is primarily used to collect device data, and it operates as a deployment. Once the Mapper is deployed, the operating data of the device can be retrieved. In this practice scenario, the temperature and humidity values collected by the Mapper can be seen on the device details page.

In real application scenarios, you can modify the implementation and behavior of the Mapper according to business needs to complete DMI standard functions such as data push, data pull, data storage in databases, edge-side localization processing, and device linkage.

Note

The order of creating end devices and deploying the Mapper device can be swapped.

Check the image address of mapper device:

release-ci.daocloud.io/kant/devicedemo:v1.1

For the deployment process of Mapper device , refer to Creating Deployments.

Parameters for creating deployments:

  • Container Settings -> Data Storage : Choose Host Path, map HostPath /etc/kubeedge to mountPath /etc/kubeedge, and set the permission to Read/Write.
  • Advanced Settings -> Network Configuration : Select Host Network as the network type.

  • Advanced Settings -> Node Scheduling : Choose the same node that is bound to the device.

Verifying Device Operation

After completing the above steps, you can go to the device details page, and see the operating data of the device on the interface. In this scenario, you will see the temperature and humidity values. In this article, the data values of the mock device will not change.

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