Allen-Bradley API Reference

{
  "create_ts":"2023-09-19T20:37:12.678Z",
  "scada0":10,
  "scada1":20,
  "scada2":30,
  "scada3":40,
  "scada4":50,
  "scada5":60,
  "scada6":70,
  "scada7":80,
  "scada8":90,
  "scada9":100,
  "temperature":86.230003356933594,
  "message":"AB rocks            "
}

The Maximal request configures the Allen-Bradley connector to collect data from a ControlLogix PLC at address 192.142.100.22 every 5 seconds. It collects data from 3 tag addresses named "scada", "temperature", and "message" . If it cannot read the tags within 1 second, it returns a timeout error. 

In this example, the connector retrieved ten 32-bit integers from the PLC starting at the "scada" tag address and added each integer to the generated JSON as a separate property named "scadaN" where N is the zero-based array index number. In the PLC, the "scada" tag had an array containing the following ten integer values: [10, 20, 30, 40, 50, 60, 70, 80, 90, 100]. The generated JSON included the corresponding ten properties: "scada0":10, "scada1":20, "scada2":30, "scada3":40, "scada4":50, "scada5":60, "scada6":70, "scada7":80, "scada8":90, "scada9":100.

The connector also retrieved one Floating point number from the PLC starting at the tag address "temperature" and added it to the generated JSON as a property named "temperature". Because the connector retrieved only one value, it did not append an index number to the end of the "temperature" property name.  In the PLC, the "temperature" tag was a floating-point number 86.230003356933594. The generated JSON included the corresponding property "temperature":86.230003356933594.

The connector then retrieved a 20-byte string from the PLC starting at the tag address "message" and added it to the generated JSON as a property named "message". Because the connector retrieved only one value, it did not append an index number to the end of the "message" property name. In the PLC, the "message" tag was the 20-byte string "AB rocks            ". The generated JSON included the corresponding property "message":"AB rocks            ".

The connector receives the collected JSON data in the source_payload field of a JSON document, and inserts it in a record in the "abTable1" table.

"tagName" options

If you want to read an array starting in the middle, add the first position inside square brackets as part of the tag name.

For example, the following request values would generate the following retrieved data.

Request values

{
  "tagPath":"1,0",
  "tagName":"scada[4]",
  "tagElementCount":3,
  "tagType":"int32",
  "propertyPath":"scada"
}

Retrieved data

{
  "create_ts":"2023-09-26T19:01:39.714Z",
  "scada0":50,
  "scada1":60,
  "scada2":70
}

In this example, the "scada" tag represents an array in the PLC containing the following ten integer values: [10, 20, 30, 40, 50, 60, 70, 80, 90, 100]. The tag array is zero-based.

The first element is [0] so "tagName": "scada[4]" collects data at the 5th item in the array, which has the value of 50. Specifying "tagElementCount": 3 collects 3 items from the array.

The connector generates JSON containing the properties "scada0":50, "scada1":60, and "scada2":70. These properties correspond to the properties named "scada4":50, "scada5":60, and "scada6":70 in the results from the Maximal example.