MQTTPublishMeta()

Publish custom metadata called by the CRBasic program.

Syntax

MQTTPublishMeta (Result, “TableName”, “FieldName”, “Key”, “Value”, “OptionalTopicSegment”)

• Result {float | long} : Response code

  • 0 = Success

  • -1 = No MQTT connection

  • -2 = TableName or FieldName not found

  • -5 = System error

  • -6 = Did not run

• "TableName" {string} or {NULL string “”} : Specifies what data table to target. The TableName will be included in the topic structure. If a null string is supplied, the segment is omitted from the topic structure.

• "FieldName" {string} or {NULL string “”} : Specifies what field name in a data table to target. The FieldName will be included in the topic structure. If a null string is supplied, the segment is omitted from the topic structure.

• "Key" {string} : Specifies the JSON key to publish. The provided Key is used directly as the JSON key and is paired with the value supplied in Value.

• "Value" {float | long | string | boolean | double} : The provided Value is encoded into JSON and published as the JSON value for the given Key.

• "OptionalTopicSegment" {string} (Optional) : Adds an extra topic level. When provided, this segment is appended to the topic structure where the Key and Value are published.

Topic Structure <base topic>/pr/<UID>/metadata/#

Example Topic Structures Based on Parameters

• MQTTPublishMeta(meta_data_result, “”, “”, “<Key>”, “<Value>”)

  • Topic <base topic>/pr/<UID> /metadata

• MQTTPublishMeta(meta_data_result, “”, “”, “<Key>”, “<Value>”, “<OptionalTopicSegment>”)

  • Topic <base topic>/pr/<UID> /metadata/<OptionalTopicSegment>

• MQTTPublishMeta(meta_data_result, “<TableName>”, “”, “<Key>”, “<Value>”)

  • Topic <base topic>/pr/<UID> /metadata/<TableName>

• MQTTPublishMeta(meta_data_result, “<TableName>”, “<FieldName>”, “<Key>”, “<Value>”)

  • Topic <base topic>/pr/<UID> /metadata/<TableName>/<FieldName>

• MQTTPublishMeta(meta_data_result, “<TableName>”, “<FieldName>”, “Key”, “Value”, “<OptionalTopicSegment>”)

  • Topic <base topic>/pr/<UID> /metadata/<TableName>/<FieldName>/<OptionalTopicSegment>

• MQTTPublishMeta(meta_data_result, “<TableName>”, “”, “Key”, “Value”, “<OptionalTopicSegment>”)

  • Topic <base topic>/pr/<UID> /metadata/<TableName>/<OptionalTopicSegment>

Data Format Structure

Payload JSON

{
  "notice": {
    "UID": "<UID>",
    "timestamp": "yyyy-mm-ddThh:mm:ss",
    "<Key>": "<Value>"
  }
}

CRBasic Example

Const LONGITUDE = -111.8549
Const LATITUDE  = 41.7666
Const ALTITUDE  = 4498

Public engine_rpm As Long
Public fuel_level As Float
Public pto_engaged As Boolean
Public tire_pressure(4) As Float
Public meta_data_result
Public trigger as Boolean

DataTable (Deere_4020_Chart, 1, -1)
  DataInterval (0, 10, Sec, 10)
  Sample (1, engine_rpm, Long)
  Sample (1, fuel_level, IEEE4)
  Sample (1, pto_engaged, Boolean)
  Sample (4, tire_pressure(), IEEE4)
  MQTTPublishTable (1, 0, 10, Sec, 2, LONGITUDE, LATITUDE, ALTITUDE)
EndTable

'Main Program
BeginProg

  'Test Values
  engine_rpm        = 1800
  fuel_level        = 100
  pto_engaged       = True
  tire_pressure(1)  = 32.1
  tire_pressure(2)  = 32.2
  tire_pressure(3)  = 35.1
  tire_pressure(4)  = 35.2

  Scan (10, Sec, 0, 0)

    'Trigger MQTTPublishMeta() Examples:
    If trigger = True Then
      trigger = False   ' reset trigger

      '1 - Topic: <base topic>/pr/<UID>/metadata
      ' - Only the key:value are used
      MQTTPublishMeta (meta_data_result, "", "", "farm_name", "Twin Pines")

      '2 - Topic: <base topic>/pr/<UID>/metadata/established
      ' - OptionalTopicSegment = established
      MQTTPublishMeta (meta_data_result, "", "", "date", "11/05/1955", "established")

      '3 - Topic: <base topic>/pr/<UID>/metadata/Deere_4020_Chart
      ' - TableName = Deere_4020_Chart
      MQTTPublishMeta (meta_data_result, "Deere_4020_Chart", "", "VIN", "JD4020-000001")

      '4 - Topic: <base topic>/pr/<UID>/metadata/Deere_4020_Chart/engine_rpm
      ' - TableName = Deere_4020_Chart
      ' - FieldName = engine_rpm
      MQTTPublishMeta (meta_data_result, "Deere_4020_Chart", "engine_rpm", "rpm_range", "1500-2202")

      '5 - Topic: <base topic>/pr/<UID>/metadata/Deere_4020_Chart/engine_rpm/pto_rpm
      ' - TableName = Deere_4020_Chart
      ' - FieldName = engine_rpm
      ' - OptionalTopicSegment = pto_rpm
      MQTTPublishMeta (meta_data_result, "Deere_4020_Chart", "engine_rpm", "pto_rpm", "540", "pto_rpm")

      '6 - Topic: <base topic>/pr/<UID>/metadata/Deere_4020_Chart/engine_type
      ' - TableName = Deere_4020_Chart
      ' - OptionalTopicSegment = engine_type
      MQTTPublishMeta (meta_data_result, "Deere_4020_Chart", "", "type", "6.6L Diesel", "engine_type")
    EndIf

    CallTable Deere_4020_Chart

  NextScan
EndProg

Example Data

The following example data corresponds to the 4th example in the CRBasic example.

Subscribe cs/v2/pr/ABCD-EFGH-1234/metadata/Deere_4020_Chart/engine_rpm

{
  "notice": {
    "UID": "ABCD-EFGH-1234",
    "timestamp": "2026-01-31T12:14:00",
    "rpm_range": "1500-2202"
  }
}