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IO-Link

logiccloud Control can connect to an IO-Link master that exposes a REST API (JSON over HTTP), poll process data and parameters from the master’s ports and connected devices, and write values back. To do this, a new connection of type IO-Link must be created and parameterized in the connection settings of the respective runtime.

Section titled “Create a new IO-Link connection”

Select Add IO-Link connection and enter the REST endpoint of the IO-Link master together with its credentials. After the connection has been created, select it in the outline tree to edit its configuration.

Connection settings:

  • Name: Name of the connection
  • Description: Description, optional
  • Url: base URL of the IO-Link master’s REST endpoint
  • Username: user name for authenticating against the master
  • Password: password for authenticating against the master

Read and write resources

Section titled “Read and write resources”

An IO-Link connection is organised into resources. A resource points at a specific part of the master’s REST tree — the gateway, a master, a master port, or a connected device — and carries the variable mappings for the values found under that path.

  • Read resources poll the master at a fixed interval and map the returned JSON values onto Input program variables.
  • Write resources push values from Output program variables back to the master.

When addressing a resource you select what it points at (for example a device alias, a master number and port number, or a resource path such as /processData/values). Process-data values are read and written through the device’s IODD description, so values are exposed by their IODD names rather than raw byte arrays.

Read resource settings:

  • Poll interval: interval (ms) at which the resource is polled from the master

Write resource settings:

  • Payload: payload template written to the resource
  • Write mode: when the value is written — on change (write only when the mapped value changes), time triggered (write at a fixed interval) or buffered on change (write on change but buffered over an interval)
  • Write interval: interval (ms) used by the time-triggered / buffered write modes

Mapping process variables

Section titled “Mapping process variables”

Each resource carries a list of mappings between a JSON value and a program variable:

  • Variable name: the program variable that will be mapped
  • Json path: the path to the value in the JSON payload returned by the master
  • Value path: the path pointing to the value inside the IODD structure (under the JSON path)
  • Data type: data type of the value — used when reading/writing raw byte-array values (BooleanT, StringT, IntegerT, UintegerT, Float32T, TimeSpanT, TimeT, ByteArrayT)