Payload Design

Designed in a way to ensure same code can be used for both gateway as well as sensor.

Payload from sensor can be directly passed as data for gateway payload and so on to higher levels.

This ensures that the code used to extract data is reusable at multiple levels.

Gateway Payload

{
    "device": {
        "type": "gateway",
        "id": "001"
    },
    "message": {
        "metadata": {
            "condition": {
                "bat_percentage": 86.7,
                "cycle_count": 226,
                "status": 1,
                "temp": 6,
                "time": 0,
                "voltage": 3.6
            },
            "settings": {
                "property": "value"
            }
        },
        "data_count": 2,
        "data_list": [
            "+++SENSOR_PAYLOAD_1+++",
            "+++SENSOR_PAYLOAD_2+++"
        ],
        "published_at": "2020-01-15T16:02:10.778Z"
    }
}

Sensor Payload

{
    "device": {
        "type": "sensor",
        "id": "sensor_id"
    },
    "message": {
        "metadata": {
            "condition": {
                "bat_percentage": 86.7,
                "cycle_count": 226,
                "status": 1,
                "temp": 6,
                "time": 0,
                "voltage": 3.6
            },
            "settings": {
                "property": "value"
            }
        },
        "data_count": 2,
        "data_list": [
            {
            "sensor_type": "Temperature",
            "value": 31,
            "unit": "C"
        },{
            "sensor_type": "Accelerometer",
            "value": "x: 0.0, y: 0.0, z: 0.0",
            "unit": "m/s^2"
        }
        ]
        "published_at": "2020-01-15T16:02:10.668Z"
    }
}

Example

 const sensor_payload = createPayload({
            type: "sensor",
            id: "0001",
        }, {
            bat_percentage: 86.7,
            cycle_count: 226,
            status: 1,
            temp: 6,
            time: 0,
            voltage: 3.6
        }, {
            property: "value"
        },
        [{
            sensor_type: "Accelerometer",
            value: {
                x: Math.random() * 2 - 1,
                y: Math.random() * 2 - 1,
                z: Math.random() * 4 + 7.801
            },
            unit: "m/s^2",
        }],
        new Date().toISOString()
    )

const gateway_payload = createPayload({
            type: "gateway",
            id: "01",
        }, {
            bat_percentage: 86.7,
            cycle_count: 226,
            status: 1,
            temp: 6,
            time: 0,
            voltage: 3.6
        }, {
            property: "value"
        }, [sensor_payload],
        new Date().toISOString(), )

device.publish(
    iot_topic,
    JSON.stringify(gateway_payload)
);

const createPayload = (device, condition, settings, data, published_at) => {
    return {
        device,
        message: {
            metadata: {
                condition,
                settings
            },
            data_count: data.length,
            data,
            published_at
        }
    }
}