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PLC definition know-how

Since with B&R web server priority is to low and no multi core CPU support is available. Service Ui is faced with many time out challenges while loading plc definition from B&R web server (REST API). There are multiple strategies implemented to handle time out challenges.

plc-definition-mode

Cached

Default setting with B&R PLC. PLC definition is read from B&R web server: http://localhost/service-ui/plc-definition/. If a request is successful, the response is cached to user working directory from Service Ui: .cache/HOST_NAME/plc-definition/. If a request is failed (time out, invalid web server configuration, ...), Service Ui is searching plc definition file from local .cache directory.

Restrictions

  • Since Service Ui reads items-br.json/items-s7tia first after execution. If REST API request always fails, new item definition is not available. That state is indicated with yellow REST state. Use Configuration/PLC connect slider to reconnect.
    plc-definition-cache
  • Since full PLC definition is separated into hundred of files. There is no crawl algorithm for caching, only anyway requested files will written into cache.

Online

PLC definition file request to PLC web server only. This is the behavior with older Service Ui versions.

Local

Since Siemens S7 Tia web server is not integrated. This is the default behavior with Siemens S7 target.

All PLC definition files will read from Service Ui user working directory: plc-definition/. Full plc definition file tree is generated by UPbuild__ServiceUiBackend build config directly.

Restrictions

  • To update plc defintions, execution of generate command at ServiceUiBackend target folder is required.
  • Version of connected PLC must be compatible to generated plc-definition folder at ServiceUiBackend user working directory.