Troubleshoot Device Connectivity Status

Estimated reading time: 2 minutes

At times, a device may display as Disconnected, as in the following example.

Why is the Device Disconnected?

Certain conditions cause a PLC to be disconnected in OT Link Platform.

Condition Reasons PLC Appears as Disconnected Steps to Connect the Device

Free Tag: Explicit register name required

  • Certain device drivers, such as Allen-Bradley CompactLogix, will not have a list of register names in the DeviceHub Add Tag form.
  • When a list of registers is not provided, the case-sensitive register name must be entered exactly as it is defined in the PLC.
  • In these cases, the device will not display a Connected status until a tag with a correct register name is created.
  1. See DeviceHub Add a Tag and DeviceHub Manage Tags to add a tag with a case-sensitive register name.
HID Device in Wait State
  • Some HID (Human Interface Devices), such as barcode scanners, are always disconnected and only show a connected status when they send data to OT Link Platform.
  1. This is a temporary state and no intervention is required. The device will connect when there is data to receive.
Incorrect PLC Configuration
  • If configuration changes have been made to a PLC, the best way to ensure accurate OT Link Platform status is to delete and recreate the DeviceHub Device.
  1. Delete the DeviceHub Device. See DeviceHub Add, Monitor, or Delete Device.
  2. Create a new DeviceHub Device with the correct PLC configuration.
Incorrect Tag Information
  • To prevent the PLC from going into fail safe mode or from crashing the process when a tag has incorrect information, OT Link Platform disconnects communication with the PLC.
  • For example, a tag may contain an incorrect address.
  1. Monitor all the tags in Flows to identify the bad tag.
  2. Find the tag with a success flag set to false.
  3. Delete the tag from DeviceHub. See DeviceHub Manage Tags.
  4. If there is no data on the flows, restart the PLC. If a node in a flow indicates "waiting for messages" and nothing is displayed in the debug console, this means that OT Link Platform has stopped communicating with the PLC, so there is no data.