Open Control Architecture

The Open Controls described on this site works as follows:

• Communications between systems is performed using MQTT using a standardised 5 level topic structure. network / node / device / group / key.
• A device managing communications is called a node.
• Data from within a node or from connected devices is assigned a local network identifier of "local" so that the node can separate internal traffic and readings from general traffic. This is stored under global.localNetworkId
• The external network identifier is stored under global.networkId
• The node identifier is stored under global.node
• Attributes for data may be loaded from a central index (GitHub hosted), providing additional information such as units and descriptions. This is to avoid the need to locally describe data, and to assist in compatibility.
• Controls software is written in Node-RED.
• Within Node-RED, data and attributes are stored within the global.readings object.
• Persistent settings for a node (or application) are held on disk and in the global.settings object. This is for local operational settings.
• Persistent settings for local devices are held on disk and in the global.deviceSettings object, and are specific to a device (or node).
• Data within the readings object is nested according to the topic (excluding the node as more than one node may publish data on a device).

e.g. a message with a topic myNetwork/node123/myDevice/dat/outputTemperature  would be stored in (global).readings.myNetwork.myDevice.dat.outputTemperature.value

Internally, message topics can be truncated and the network and node will be filled in. The data group will be assumed to be dat is not supplied.

e.g. a message with a topic setpoint  would be stored in (global).readings.local.myNode.dat.setpoint.value

Within Node-RED the current data can be viewed in the data explorer.

The following code could be used to read data and its attributes for output.

 var localNetworkId = global.get("localNetworkId");
 var node = global.get("node");

 var reading = global.get("readings." + localNetworkId + "." + node + ".dat.outputTemperature");

 var output = "The value of " + reading.title + " is " + reading.value + reading.units;  
 // "The value of Output Temperature is 35°C