AWS IoT SiteWise with raspberry pi Temperature Sensor DS18B20 Part II

Now that we have a sensor connected we need to expose the data to AWS sitewise

The most direct means I could find of accomplishing this was by installing an OPC UA server on the raspberry PI. So, on to another tutorial. To do so I ended up using http://node-opcua.github.io/#

At first this looked perfect

https://github.com/node-opcua/node-opcua/blob/master/documentation/monitoring_home_temperature_with_a_raspberry.md but I couldn’t quite get it to work…

So I ended up modifying the sample_server.js from https://github.com/node-opcua/node-opcua/blob/v2.1.3/documentation/sample_server.js

The Install

Assuming you are on raspbian:

  • make sure to have nodejs and npm command installed
$ node --version
$ npm -version

installing node-opcua as a node package

$ mkdir mytest
$ cd mytest
$ npm init 
$ npm install node-opcua --unsafe-perms

next edit (create) the sample_server.js in nano

$ nano sample_server.js

Copy the below and ctrl + X to write out the file.

/*global require,setInterval,console */
const opcua = require("node-opcua");

const readline = require('readline');
const fs = require('fs');



// Let's create an instance of OPCUAServer
const server = new opcua.OPCUAServer({
    port: 4334, // the port of the listening socket of the server
    resourcePath: "", // this path will be added to the endpoint resource name
     buildInfo : {
        productName: "MySampleServer1",
        buildNumber: "7658",
        buildDate: new Date(2014,5,2)
    }
});

function post_initialize() {
    console.log("initialized");
    function construct_my_address_space(server) {
    
        const addressSpace = server.engine.addressSpace;
        const namespace = addressSpace.getOwnNamespace();
    
        // declare a new object
        const device = namespace.addObject({
            organizedBy: addressSpace.rootFolder.objects,
            browseName: "MyDevice"
        });
    
        // add some variables
        // add a variable named MyVariable1 to the newly created folder "MyDevice"
        let variable1 = 1;
        
        // emulate variable1 changing every 500 ms
        setInterval(increment, 500);

        function increment() {
            
            const readInterface = readline.createInterface({
                    input: fs.createReadStream('/sys/bus/w1/devices/28-01145ecb4ea5/w1_slave')
            });

            readInterface.on('line', function(line){
                // exclude the 'YES' line, only process second line
                if (line.includes('YES')){
                    // ignore
                } else {
                    // split the t=
                    split = line.split("t=");
                    // convert to c
                    temp_c = split[1] / 1000.0;
                    temp_f = temp_c * 9.0 / 5.0 + 32.0;
                    variable1=temp_f;
                }
                
            });
               
            
           
        }
        
        namespace.addVariable({
            componentOf: device,
            browseName: "Temperature",
            dataType: "Double",
            value: {
                get: function () {
                    return new opcua.Variant({dataType: opcua.DataType.Double, value: variable1 });
                }
            }
        });
        
        // add a variable named MyVariable2 to the newly created folder "MyDevice"
        let variable2 = 80.0;
        
        namespace.addVariable({
        
            componentOf: device,
        
            nodeId: "ns=1;b=1020FFAA", // some opaque NodeId in namespace 4
        
            browseName: "Baseline",
        
            dataType: "Double",    
        
            value: {
                get: function () {
                    return new opcua.Variant({dataType: opcua.DataType.Double, value: variable2 });
                },
                set: function (variant) {
                    variable2 = parseFloat(variant.value);
                    return opcua.StatusCodes.Good;
                }
            }
        });
        
    }
    construct_my_address_space(server);
    server.start(function() {
        console.log("Server is now listening ... ( press CTRL+C to stop)");
        console.log("port ", server.endpoints[0].port);
        const endpointUrl = server.endpoints[0].endpointDescriptions()[0].endpointUrl;
        console.log(" the primary server endpoint url is ", endpointUrl );
        
    });
}
server.initialize(post_initialize);

Some Niceties

install screen so you can detach from the session

sudo apt-get install screen

run the sample server using screen

screen node sample_server.js
1.Detach a terminal
CTRL + A release, and then press D
2. List all terminal session
$ screen -list
3. Reconnect screen
$ screen -r

Assuming it works

Now that you have an opcua server running, its a good idea to try and connect to it. See that opc.tcp address, copy that out to use. (You might have to replace with the ip address if you don’t have DNS resolution)

Then download the commserver opcua client http://www.commsvr.com/Products/OPCUAViewer/tabid/520/language/en-US/Default.aspx you have to fill out a registration (annoying) but other than that its pretty easy.

Start the application, paste in the address, and hit connect. Set all the security to none

Hit OK,

Then Hit OK again. If everything worked you should see this

When it complains about the certificate, hit yes to trust it. You should see something like this

Right click on Temperature, subscribe, new, and then OK

If you grab the probe you should see the value of the Temperature change.

Part III https://michaelellerbeck.com/2020/01/14/aws-iot-sitewise-with-raspberry-pi-temperature-sensor-ds18b20-part-iii/

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