Adding new sensors

This section explain how to add new sensors to the webhook server by editing the formatData function and addData function in the index.js file.

WEBHOOKS

If you need more information about the webhooks sent from the things stack you can checkout the documentation here.

You can also learn more about the JSON file sent by the webhook here

We also use a custom payload formatting script which you can read more about here

The formatData function

The JSON file

The format data function takes in the JSON file sent by things stack webhook and formats it into an array that makes it easier for the addData function to insert data into the database. The array returned a the end of the function contains the variables sensorData, sensorType, SensorboxConnector and sensorboxID. To get data into these variables you need to get them from the JSON file. The JSON file from things stack is formatted in this way.

{
  {
    "f_port": 1,
    "frm_payload": "AAAAAAAAAAA=",
    "decoded_payload": {
      "dataArray": ["0","0","0","0","0","0"],
      "plugg": "0",
      "sensor": "0"}
  },
  "rx_metadata": [{
        "gateway_ids": {
          "gateway_id": "test"
        },
        "rssi": 42,
        "channel_rssi": 42,
        "snr": 4.2
  }]
}
//there is more in the message sent from things stack 
//but we dont need more of the message than this

To get data into the variables you use a . to go index the key-value pairs. This is done like this in the formatData function.

• sensorData = data.uplink_message.decoded_payload.dataArray //from the example above this will be an array ["0","0","0","0","0","0"]

• sensorType = data.uplink_message.decoded_payload.sensor //from the example above this will be "0"

• sensorboxConnector = data.uplink_message.decoded_payload.plugg //from the example above this will be "0"

• sensorboxID = data.end_device_ids.device_id //from the example above this will be "0"

Adding new sensors to the function

To add new sensors to the function you need to add a new case in the switch with the sensor type as the case. The case should format the hexadecimal values in the sensorData array into usable values for the database. The webserver contains three useful functions for formatting the hexadecimal values, hexToDecimal , hexToNegOrPosNum and the float-array-to-string.

• hexToDecimal() //takes in a hex value and converts it to a decimal value

• hexToNegOrPosNum() //takes in a 4 byte hex value as a string and converts it to either a negative or positive decimal

• float-to-array-to-string//not used in this version of the server but converts an 4 byte array of hex values into a float value and vice versa

Three examples using the hexToDecimal function, the hexToNegOrPosNum function and the float-array-to-string function.

case 48: //Soil humidity
    sensorData = hexToDecimal(sensorData[0]+sensorData[1]) //takes the hex values from sensordata combines them and turns them into decimal 
    returnArray = [sensorType,sensorboxID,sensorboxConnector,sensorData]
    break;

case 61: //SCD30 Sensor
    //diffrent sensor values
    var co2Sensor = hexToDecimal(sensorData[0]+sensorData[1]) //takes hex values at place [0],[1],[2] and [3] from sensorData and decodes them to a float value
    var tempSensor = hexToNegPosNum(sensorData[2]+sensorData[3]+sensorData[4]+sensorData[5]) //takes hex values at place [4],[5],[6] and [7] from sensorData and decodes them to a float value
    var humiditySensor = hexToDecimal(sensorData[6]+sensorData[7])  //takes hex values at place [8],[9],[10] and [11] from sensorData and decodes them to a float value 

const floatConverter = require("float-array-to-string") //float-array-to-string is declared further up in the code 

case 61: //SCD30 Sensor
    var co2Sensor = floatConverter.decodeFloatArr(sensorData.slice(0,3)) //takes hex values at place [0],[1],[2] and [3] from sensorData and decodes them to a float value
    var tempSensor = floatConverter.decodeFloatArr(sensorData.slice(4,7)) //takes hex values at place [4],[5],[6] and [7] from sensorData and decodes them to a float value
    var humiditySensor = floatConverter.decodeFloatArr(sensorData.slice(7,11)) //takes hex values at place [8],[9],[10] and [11] from sensorData and decodes them to a float value
    sensorData = [co2Sensor,tempSensor,humiditySensor] //places co2, temp and humidity data into sensordata
    returnArray = [sensorType,sensorboxID,sensorboxConnector,sensorData] //returns [sensorType, sensorboxID,sensorboxConnector, sensorData[float,float,float],]
    break;

At the end of the function you need to return the array in this order for the function to be compatible with the addData function.

returnArray = [sensorType, sensorboxID, sensorboxConnector, sensorData]

The addData function

The addData function queries the database and inserts the data from the data variable.

To add a new sensor you need to add a new case with the sensor address as the case. The insertRow variable in the case should be a SQL query to insert data into the database in this format.

• DATA[0] = sensorbox_type

• DATA[1] = sensorbox_ID

• DATA[2] = sensorbox_connector

• DATA[3] = sensor value

case "sensor adress": //inserts data into the database and prints it to the console
    insertRow = await client.query(`INSERT INTO "Skjetleingard_test"(sensor_type,sensorbox_id,sensorbox_connector,value) VALUES(${data[0]},'${data[1]}',${data[2]},${data[3]});`)
    console.log(`Inserted ${insertRow} row`);
    break;

If you get more than one value from your sensor the formatData function will return an array as DATA[3] to insert the values into the database then you could do something like this.

insertRow = await client.query(`INSERT INTO "Skjetleingard_test"(sensor_type, sensorbox_id, sensorbox_connector, value1, value2) VALUES(${data[0]},${String(data[1])},${data[2]},${data[3][0]},${data[3][1]});`)

Normal errors:

If you run the webserver and get an message in the console that say error at "xxxxxxx" or column does not exist. You need to remember to add single quotes around the data[1] variable that contains the sensorbox_id like this '${data[1]}'