====== MQTT ======


===== Basic properties and requirements =====

  * MQTT versions 3.1.0 a and **3.1.1** are supported
  * Any device must be registered in the Mervis cloud. Connection parameters are provided upon the registration (**DeviceID**, **user name** and **password**)
    * Contact [[en:help:support|]].
  * possibility of a dynamic variable set (devices can specify what variables they publish)
  * only built-in types are supported (bool, integers, floating point numbers, string)
  * support for secured channel. A device can use secure or non-secure connection

===== General behavior of the clients =====

==== Connect ====

  * ClientID corresponds to the DeviceID
  * User name and password
  * No special requirements considering flags or keep-alive periods (some reasonable value like 60 seconds are recommended)

==== Publish/Subscribe ====

  * Every topic starts with the DeviceId
  * The rest of the topic depends on the required functionality

===== Supported formats =====

==== Wago compatible format ====

=== Registration of available variables ===

  * Informs the subscribers of available variables
  * Publish message with “At least once delivery”
  * Topic: deviceId/TagConfiguration
  * Combination of the collection ID and Tag must be unique for every device!
  * Payload: UTF-8 JSON document
    * /FormatId: (string), message ID
    * /ApiVersion(int), version of API
    * /Complete (bool), must be true now
    * /Collections (Array of collection elements)
      * /Id (int), ID of the collection
      * /CollectionName (string)
      * /SampleRate (int), collection sample rate in ms
      * /PublishInterval (int), collection publish interval in ms
      * /TagData (Array of variable descriptions)
        * /Tag (string), ID of the variable
        * /Unit (string), unit of the variable
        * /ValueType (string), ST type; only simple types are supported

**Example**

<code json>
{
	"FormatId": "TagConfiguration",
	"ApiVersion": 1,
	"Complete": true,
	"Collections": [{
		"Id": 1,
		"CollectionName": "Building 1",
		"SampleRate": 60000,
		"PublishInterval": 60000,
		"TagData": [{
			"Tag": "Temperature1",
			"Unit": "ºC",
			"ValueType": "real"
		},
		{
			"Tag": "Humidity",
			"Unit": "%",
			"ValueType": "word"
		}]
	},
	{
		"Id": 2,
		"CollectionName": "Building 2",
		"SampleRate": 120000,
		"PublishInterval": 240000,
		"TagData": [{
			"Tag": "Water flow",
			"Unit": "m3/h",
			"ValueType": "byte"
		},
		{
			"Tag": "Current phase L1",
			"Unit": "A",
			"ValueType": "lreal"
		}]
	}]
}
</code>

=== Variable values ===
  * Publishes values of variables
  * Publish message with “At least once delivery”
  * Topic: deviceId/TagValues
  * Payload: UTF-8 JSON document
    * /FormatId: (string), message ID
    * /ApiVersion(int), version of API
    * /CollectionId (int), identification of the collection
    * /TagData (Array of value items)
      * /Time (datetime), timestamp in ISO format (YYYY-MM-DDTHH:MM:SSZ), ideal is a UTC form
      * /Values (Collection of Tag and value tuples)

**Example**

<code json>
{
	"FormatId": "TagValues",
	"ApiVersion": 1,
	"CollectionId": 1,
	"TagData": [{
		"Time": "2018-03-27T17:19:23.720+02:00",
		"Values": {
			"Temperature1": 15.52,
			"Humidity": 21
		}
	}]
}

</code>
==== Weintek compatible format ====
  * We assume that all datetime values are in **UTC**
  * Print screens are from EasyBuilder Pro SW
=== Variable values ===
  * Publishes values of variables
  * Publish message with “At least once delivery”
  * Topic: $deviceId/mervis/values or $deviceId/mervis/values/*
  * Payload: UTF-8 JSON document
    * /d: root element
      * "property_name": value - property name, can contain metada(not required). Always use array [...] for value of property
        * metadata format:
          * "name" name of property
          * "type" property type(we supported only [[https://kb.mervis.info/doku.php/en:mervis-scada:80-mqtt#our_supported_types|our list of types]])
          * "unit" information about unit of value

**Example**

<code json>
{
    "d" : {
        "name:MyHomeTemperature, type:generic_sint64, unit:°C" : [ 0 ],
        "number C" : [ 0 ],
        "Bit" : [ false ],
        "My array" : [ 0, 10, 20 ]
    },
    "ts" : "2020-08-27T07:10:24.360316"
}

</code>
{{ :en:mervis-scada:annotation_2020-08-27_120101.png?600 |}}
=== Command registration ===
  * Topic: $deviceId/mervis/cmd_reg or $deviceId/mervis/cmd_reg/*
  * Format:
    * /d root element
      * "propertyName" must include some informations(separate by ","). Value is ignored.
        * "id" what is command id and define subscribe topic ($deviceId/mervis/command/change_temperature)
        * "name" just for customer info
        * "params" parameters with informations to command (**must include all parameters of supscribe topic**)
          * "name" parameter name in json
          * "type" type of parameter (we supported only [[https://kb.mervis.info/doku.php/en:mervis-scada:80-mqtt#our_supported_types|our list of types]])
          * "unit" information about unit of parameter
        * "ts" time span 
<code>
{
    "d" : {
        "id:change_temperature, name:change temperature in house ,params:[{name: temperature, type:generic_float64, unit:°C}, {name: date, type:generic_datetime, unit:UTC}]" : false
    },
    "ts" : "2020-08-27T07:10:11.356013"
}
</code>
choose/create $deviceId/mervis/cmd_reg/
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set general tab by screenshot
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add commands
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===Our supported types===
              * "generic_bool"
              * "generic_sint8"
              * "generic_uint8"
              * "generic_sint16"
              * "generic_uint16"
              * "generic_sint32"
              * "generic_uint32"
              * "generic_sint64"
              * "generic_uint64"
              * "generic_float32"
              * "generic_float64"
              * "generic_string"
              * "generic_datetime"
===Create a subcribe topic for executing command===
  * for previous command example
  * create topic $deviceId/mervis/command/change_temperature
  * with two addresses:
    * temperature(32-bit float)
    * date(string)
{{ :en:mervis-scada:annotation_2020-08-27_110134.png?600 |}}