MQTT Library

Library

The mqtt library exposes three things that should be used to send sensor data to Stemi's datastore. These are:

• mqtt (of type StemiMqtt)
• SensorData
• SensorPacket

mqtt.py

mqtt = None # variable that will hold the mqtt client instance instance

class SensorData:
    SENSOR_TYPES = ["Light", "Pressure", "AirHumidity",
                    "SoilHumidity", "AirTemperature", "SoilTemperature"]

    def __init__(self, type: str, value: float):
        ...

class SensorPacket:
    def __init__(self, init=None):
        ...

    def add(self, packet: SensorData):
        ...

class StemiMqtt:
    def publish(self, topic: str, packet: SensorPacket):
        ...

    def reconnect(self):
        ...

Explanations

	Returns	Description
SensorData		A class that holds a sensor's type information and it's value, a data point
SensorData.SENSOR_TYPES		Preferred types of sensor data, this information will be used later in data analysis, if the user enters some other value, it will be overridden to Other
SensorData.__init__()	An instance of SensorData	Creates a sensor data point that can be sent to the datastore
SensorPacket		A class that hold multiple sensor data points
SensorPacket.__init__()	An instance of SensorPacket	Creates an instance of SensorPacket and sets the inital data points if the variable init is passed, which should be a list of type SensorData
SensorPacket.add()		Adds another SensorData instance to the packet
StemiMqtt		A class that sends multiple data points to Stemi's datastore, should used through mqtt instance
StemiMqtt.publish()		Sends a SensorPacket to Stemi's datastore
StemiMqtt.reconnect()		Reconnects the internal mqtt client in case of a network error

Structured data example

main.py

from stemi.mqtt import mqtt, SensorPacket, SensorData

...

mqtt_topic = "stream/cl1npjxh20000t4xz5fyi42u9"

try:
    s = SensorPacket()
    s.add(SensorData('Light', ldr.value))
    s.add(SensorData('AirHumidity', aht.relative_humidity))
    s.add(SensorData('AirTemperature', aht.temperature))
    mqtt.publish(mqtt_topic, s)
except RuntimeError as e:
    mqtt.reconnect()

Unstructured data example

main.py

from stemi.mqtt import mqtt, MqttPacket

...

mqtt_topic = "stream/cl1npjxh20000t4xz5fyi42u9"

try:
    m = MqttPacket()
    m.add("This is a raw, unstructured value")
    mqtt.publish(mqtt_topic, m)
except RuntimeError as e:
    mqtt.reconnect()