Preparing an SD card

To prepare an SD card, follow the sequence of actions as described:

1. Download the latest Raspbian LITE image (available at https://www.raspberrypi.org/downloads/raspbian/).
2. Connect your SD card to a computer and use Etcher (https://etcher.io/) to flash the Raspbian .img file to the SD card.
3. Enable SSH:

cd /Volumes/boot
touch ssh

4. To enable Wi-Fi, create wpa_supplicant.conf with the following content:

network={
 ssid="YOUR_SSID"
 psk="YOUR_WIFI_PASSWORD"
}

5. Create the /home/pi/hub folder.
6. Create the /home/pi/hub/package.json file with the following content:

{
 "name": "hub",
 "version": "1.0.0",
 "description": "",
 "main": "index.js",
 "scripts": {
   "start": "node index.js",
   "test": "echo \"Error: no test specified\" && exit 1"
 },
 "author": "",
 "license": "ISC",
 "dependencies": {
   "async": "^2.4.0",
   "node-opcua": "0.0.64",
   "request": "^2.81.0"
 }
}

7. Create the /home/pi/hub/index.js file with the following content, replacing REMOTE-SERVER-ADDRESS.com and REMOTE-SENSOR-ADDRESS with real values:

var opcua = require("node-opcua");
var async = require("async");
var request = require("request");

var session, subscription;
var client = new opcua.OPCUAClient();
var sensor = "opc.tcp://REMOTE-SENSOR-ADDRESS:4334/UA/resourcePath";
var receiver = "http://REMOTE-SERVER-ADDRESS.com:8080";

async.series(
  [
    // establishing connection
    function (cb) {
      client.connect(sensor, function (err) {
        if (err) {
          console.log("Connection to " + sensor + "failed");
        } else {
          console.log("Connection successful");
        }
        cb(err);
      });
    },

    // start session
    function (cb) {
      client.createSession(function (err, res) {
        if (!err) session = res;
        cb(err);
      });
    },

    // read value
    function (cb) {
      session.readVariableValue("ns=1;s=Variable1", function (err, dataValue) {
        if (!err) console.log("Variable1 = ", dataValue.value.value);
        cb(err);
      });
    },

    // write value
    function (cb) {
      session.writeSingleNode("ns=1;s=Variable1", new opcua.Variant({
        dataType: opcua.DataType.Double,
        value: 100
      }), function (err) {
        cb(err);
      });
    },

    // subscribe to changes
    function (cb) {
      subscription = new opcua.ClientSubscription(session, {
        maxNotificationsPerPublish: 5,
        priority: 5,
        publishingEnabled: true,
        requestedLifetimeCount: 5,
        requestedMaxKeepAliveCount: 3,
        requestedPublishingInterval: 500,
      });

      subscription.on("started", function () {
        console.log("subscription id: ", subscription.subscriptionId);
      }).on("terminated", function () {
        cb();
      });

      setTimeout(function () {
        subscription.terminate();
      }, 5000);

      // install monitored item
      var monitor = subscription.monitor({
          attributeId: opcua.AttributeIds.Value,
          nodeId: opcua.resolveNodeId("ns=1;s=Variable1"),
        },
        {
          discardOldest: true,
          samplingInterval: 50,
          queueSize: 5,
        },
        opcua.read_service.TimestampsToReturn.Both
      );

      monitor.on("changed", function (dataValue) {
        console.log("Variable1 = ", dataValue.value.value);

        // send to receiver
        var data = {
          device: "sensor1",
          timestamp: Date.now(),
          Variable1: dataValue.value.value
        };
        request.post({url: receiver, form: data}, function (err) {
          if (err) console.log("Failed to send " + JSON.stringify(data) + " to " + receiver);
        });
      });
    },

    // close session
    function (cb) {
      session.close(function (err) {
        if (err) console.log("Failed to close session");
        cb();
      });
    }
  ],

  function (err) {
    if (err) {
      console.log("Failed with error:", err);
    } else {
      console.log("Successfully finished");
    }
    client.disconnect(function () {
    });
  }
);

8. Create the /home/pi/hub/Dockerfile file with the following content:

FROM hypriot/rpi-node:boron-onbuild

9. Create the /home/pi/sensor folder.
10. Create the /home/pi/sensor/package.json file with the following content:

{
"name": "sensor",
"version": "1.0.0",
"description": "",
"main": "index.js",
"scripts": {
  "start": "node index.js",
  "test": "echo \"Error: no test specified\" && exit 1"
},
"author": "",
"license": "ISC",
"dependencies": {
  "node-opcua": "0.0.64"
}
}

11. Create the /home/pi/sensor/index.js file with the following content:

var opcua = require("node-opcua");
var min = 1;
var max = 100;

var host = new opcua.OPCUAServer({
  buildInfo: {
    buildDate: new Date(2018, 8, 8),
    buildNumber: "1234",
    productName: "productName",
  },
  port: 4334,
  resourcePath: "UA/resourcePath",
});

host.initialize(function () {
  var space = host.engine.addressSpace;

  var componentOf = space.addObject({
    browseName: "browseName",
    organizedBy: space.rootFolder.objects,
  });

  var variable1 = 0;

  // generate new value
  setInterval(function () {
    variable1 = Math.floor(max - Math.random() * (max - min));
  }, 500);

  space.addVariable({
    browseName: "browseName",
    componentOf: componentOf,
    dataType: "Double",
    nodeId: "ns=1;s=Variable1", // a string nodeID
    value: {
      get: function () {
        return new opcua.Variant({dataType: opcua.DataType.Double, value: variable1});
      },
      set: function (variant) {
        variable1 = parseFloat(variant.value);
        return opcua.StatusCodes.Good;
      }
    }
  });

  host.start(function () {
    var endpoint = host.endpoints[0].endpointDescriptions()[0].endpointUrl;
    console.log("Endpoint: ", endpoint);
  });
});

12. Configure the min and max values at the beginning of the /home/pi/sensor/index.js file.
13. Create the /home/pi/sensor/Dockerfile file with the following content:

FROM hypriot/rpi-node:boron-onbuild