Use PLC4x to connect to a Siemens S7 PLC

Shifu is also compatible with Siemens S7 series PLCs in the form of PLC4X. This article will show you how to use deviceshifu-plc4x-http to integrate and interact with a Siemens S7-1200 1214C PLC.

Connection

Step 1

Before connecting to Shifu, the PLC should already be physically connected to the host computer running Shifu via Ethernet and have an IP address, here we use 192.168.0.1.

tip

If the IP address of your PLC device is not 192.168.0.1, you can change address in the edgedevice-plc4x.yaml file to the IP of your device)

Step 2

Create a folder, which in the example we named plc4x_configuration_directory. Save all four configuration files described below in this folder.

First we need a configuration file to get the IP address and device type.

click here to check deviceshifu-plc4x-deployment.yaml

apiVersion: apps/v1
kind: Deployment
metadata:
  labels:
    app: deviceshifu-plc4x-deployment
  name: deviceshifu-plc4x-deployment
  namespace: deviceshifu
spec:
  replicas: 1
  selector:
    matchLabels:
      app: deviceshifu-plc4x-deployment
  template:
    metadata:
      labels:
        app: deviceshifu-plc4x-deployment
    spec:
      containers:
      - image: edgehub/deviceshifu-http-plc4x:v0.1.1
        name: deviceshifu-http
        ports:
        - containerPort: 8080
        volumeMounts:
        - name: deviceshifu-config
          mountPath: "/etc/edgedevice/config"
          readOnly: true
        env:
        - name: EDGEDEVICE_NAME
          value: "edgedevice-plc4x"
        - name: EDGEDEVICE_NAMESPACE
          value: "devices"
      volumes:
      - name: deviceshifu-config
        configMap:
          name: plc4x-configmap
      serviceAccountName: edgedevice-sa

In the mean time, we need some common configuration files:

click here to check deviceshifu-plcs4x-configmap.yaml

apiVersion: v1
kind: ConfigMap
metadata:
  name: plc4x-configmap
  namespace: deviceshifu
data:
  driverProperties: |
    driverSku: testPlc4x
    driverImage: 
  instructions: |
    instructions:
  telemetries: |
    telemetrySettings:

click here to check deviceshifu-plc4x-service.yaml

apiVersion: v1
kind: Service
metadata:
  labels:
    app: deviceshifu-plc4x-deployment
  name: deviceshifu-plc4x
  namespace: deviceshifu
spec:
  ports:
  - port: 80
    protocol: TCP
    targetPort: 8080
  selector:
    app: deviceshifu-plc4x-deployment
  type: LoadBalancer

click here to check edgedevice-plc4x.yaml

apiVersion: shifu.edgenesis.io/v1alpha1
kind: EdgeDevice
metadata:
  name: edgedevice-plc4x
  namespace: devices
spec:
  sku: "testPlc4x" 
  connection: Ethernet
  address: 192.168.0.1 #change this accordingly
  protocol: PLC4X
  protocolSettings:
    PLC4XSetting:
      protocol: s7

Step 3

Add PLC devices in Shifu，build and start deviceShifu:

kubectl apply -f ../plc4x_configuration_directory

Operations

Shifu can read and write to the memory of PLC via HTTP requests.

Before operation, we need to start an nginx container for sending and receiving HTTP requests, the relevant command to start is as follows:

kubectl run nginx --image=nginx:1.21 -n deviceshifu 
kubectl exec -it nginx -n deviceshifu -- bash

deviceshifu-plc4x-http has two built-in commands read and write, which we can use to read and write to the devices via shifu.

tip

The command %Q0.0:BOOL in this article is a PLC4X command where Q is the name of the memory area, 0.0 indicates the address of the starting bit and its offset. BOOL is the type of data to be read (written).

If you want to know more about PLC4X commands, please go to PLC4X official website.

read

read means to read the value of the device using the corresponding command:

For example, the command curl "deviceshifu-plc4x/read?%Q0.0:BOOL" returns the address of the memory area Q0.

curl "deviceshifu-plc4x/read?%Q0.0:BOOL"; echo
{"field_%Q0.0:BOOL": "BOOL(1bit):false"}

At this point Shifu returns the status of the first indicator from left to right in the Q area. If the light is on, then it returns true, otherwise it returns false. Since the light is off, the return value is false.

write

write means to modify the value of the corresponding location through commands:

For example, the command curl "deviceshifu-plc4x/write?%Q0.0:BOOL=true" will change the first bit of Q0 to true.

curl "deviceshifu-plc4x/write?%Q0.0:BOOL=true"; echo

More

If you need to read or write multiple commands at the same time, you can connect them with &.

For example, the command curl "deviceshifu-plc4x/read?%Q0.0:BOOL&%Q0.1:BOOL" will return both the first bit and the second bit of Q0 at the same time.

The command curl "deviceshifu-plc4x/write?%Q0.0:BOOL=true&%Q0.1:BOOL=true" will change both the first bit and the second bit of Q0 to true.