Working with IoT and Real-Time Systems¶
Lucy is particularly well-suited to integrating control systems, IoT devices and other real-time systems into your work flows.
It has out of the box support for MQTT and has connectors available for all kinds of control system protocols.
Tip
Contact Eutech for a list of available connectors that you can deploy.
MQTT Connector¶
Your Lucy account comes with an Mqtt Broker allocated to it by default. You can always change it to a different server if you choose. You can view your Mqtt Broker settings from your Lucy dashboard. From there, you can edit the broker settings. Note that even though we configure a mqtt-over-websocket server as well, that isn’t currently used by Lucy. Its for your own use for testing.
Receiving MQTT messages in your model¶
You can build models that process MQTT messages in real-time. To do this, you need to setup a subscription that will receive MQTT messages on a topic and send them to Lucy as events. Your model can then listen for these events and react to them.
To setup a subscription, , click on View All Subscriptions in the MQTT weblet on your dashboard, or go to the 
menu, go to Connectors and then choose MQTT.
Here you can view a list of all subscriptions, edit them and add a new one. A subscription is made by defining an MQTT topic pattern to subscribe to, a Quality of Service, the name of the Lucy event to fire and deciding how to receive the message content.
MQTT Topic Pattern¶
This determines what topic to listen for to pick up messages. You can use wildcards or any normal pattern specifier here.
See also
MQTT Topic Patterns: https://www.hivemq.com/blog/mqtt-essentials-part-5-mqtt-topics-best-practices
Quality Of Service¶
The MQTT protocol defines differnt qualities of service to determine how safely and robust the message delivery yes. Exactly Once message delivery is the best but also most expensive. You can decide what quality level you need based on your use case. If you aren’t sure about this, select the Not Sure option. Lucy will pick an appropriate value.
Event ID¶
This is the event that will be fired in Lucy when a message is received on a topic matching the given pattern. You can fill in any name for your event. If the event has not yet been registered, it will automatically get registered.
See also
Event Stream and Event Handling for more information on how to handle events.
Content Type¶
You can tell Lucy how the message received in MQTT should be treated when sending as an event.
There are two options:
Text¶
With this option, the full message received by the MQTT broker is sent as a parameter called Payload along with the event.
In addition a parameter called Topic is sent as well, describing the actual topic that the message was sent to.
JSON Object¶
With this option, the message is parsed as a JSON object and individual key/value pairs from the JSON are sent as separate parameters along with the event. This saves you from havin to process it as JSON within your Lucy action sequence.
Tip
If you’re not sure about the payloads you might receive, its safe to send it as Text and then process it within Lucy.
Publishing to MQTT¶
Publishing messages on an MQTT topic is easy. You can use the MqttPublish block within any Lucy action sequence to publish a message on a given topic.
Processing Real-Time Data¶
There are some useful Lucy blocks for processing real-time data.
Some of them are:
Deadband¶
It’s common for values from real-time systems to fluctuate slightly and jitter. This block lets you filter out values unless they have changed by a significant amount.
For example, you may want to process a temperature reading only when it changes significantly. This block will pass its input to the output pin only if the value changes sufficiently, OR a given time window has passed.
Set Value¶
Use this to store an arbitrary value against a key. One useful use-case is storing a sensor’s value against its id. You can also set an expiry time so that if the value is stale, it will be removed.
You can use the corresponding Get Value block to read the value back.
PublishMessage¶
Use this block to publish data on the real-time Message Bus. You can make client apps that run on webpages, desktops or mobiles that can have data pushed to it in real-time using thhis block.