FAQ

Short answers to common questions about the Data Layer. Each entry links to the page with the details. Problems and error messages are described in Troubleshooting.

Each entry has a fixed anchor (for example #faq-start-broker). To find an error message, search the Troubleshooting page for it.

Platforms and broker

Do I have to change my program when I move from ctrlX OS to a PC?

Answer: No, not the node addresses, types or call patterns: they are the same on the ctrlX Data Layer and LumiScan Keryx. What changes is the connection (a PLC on ctrlX OS, the OPC UA Connector on a PC), the tools, and the names of the method results.
More: ctrlX Data Layer and LumiScan Keryx

Do I have to start the broker on a PC?

Answer: No. When an app starts and no broker answers on the PC, it starts one at tcp://127.0.0.1:5555. The broker keeps running when the apps end. Only the OPC UA Connector never starts one: start it after the apps.
More: The broker

How do I look at the nodes?

Answer: On Windows on the Keryx page http://127.0.0.1:7555/, in LumiScan Keryx Utilities, or with krxclient. On Ubuntu with krxclient. On ctrlX OS in the Data Layer view of the ctrlX OS web interface.
More: Tools

Calling functions

Should I use the handshake or the execute method?

Answer: Use the execute method for operations within about 1 s when your program can wait. Use the handshake for longer operations - the Cam Driver’s connect-camera, disconnect-camera and reset are handshakes only - or when your program must not block. Use a stream for continuous processing.
More: Choosing a Pattern

Streams

How does a PLC read stream results?

Answer: Stream results are FlatBuffers records. Switch on keep-latest-output in the module whose result you need and read its plain output nodes, or subscribe to Calibration’s plain-points.
More: Keep latest output

OPC UA

Can the OPC UA Connector use encryption or user names?

Answer: No. It accepts anonymous, unencrypted clients only. Run it on a trusted machine network, open port 4840 for the PLC only, and give observing clients a --read-only instance.
More: Security

Support

Where do I get help?

Answer: See the site-wide LumiScan FAQ, or contact customer.success@hdvisionsystems.com, +49 6221 6721905. For licences: licenses@hdvisionsystems.com.