Node-red-contrib-cip-st-ethernet-ip cycle time not respected

General
1

I have been using node-red-contrib-s7 to read tags from Siemens PLCs and I define a reading cycle time. Each cycle generates an object with the tags and enters in the flows correctly. However, when using the equivalent node node-red-contrib-cip-st-ethernet-ip to read tags from a Rockwell PLC, I notice that the cycle time is not respected, and the reading is done without a predicted time.

Thanks,

Roberto

2

It's been done time since I used that node but I suspect it does one of 2 things...

  1. Make implicit messaging & so only send data upon PLC changes (i.e. truly event based)
  2. Uses explicit messaging (polling for values) but only Enid when it notices a value change (pseudo event based)

In other words I think you only get values upon change (not at every poll)

I may be misremembering.

3

Hi Steve,

Thanks for your attention.

After speaking with experts, I was informed that the Allen Bradley PLC reading nodes work well with Control Logix but not with Compact Logix. This is my case. There are a very large number of communication errors emitted by the node. However, the tag readings are performed correctly, despite the annoying error messages. Have you heard anything about this?

Best regards,

Roberto

4

Are these errors coming out of the node (as a message) or are they thrown?

Does adding a catch node quieten the errors?

You could try raising an issue on the repository - if the author is responsive, it might get fixed? GitHub · Where software is built

5

Hi Steve,

I tried using a catch node to avoid errors, but it didn't work. I'll make a specific post about the problem.

Thanks,

Roberto

6

If you can clarify if they are thrown errors (appearing in debug output as red items) or if they are output from the node (e.g. payload="Something bad happened" or similar) I can advise.

Can you paste a screenshot?