Thanks a lot for the explanation, I will give that a try. I have a related question - does the standard allow for both string data as well as binary data of different sizes, for the same class, instance and attribute? If so, how exactly are they differentiated, or would the user have to know in advance the format of the data and process the response accordingly?
I seem to be making some progress here, but please see attached for a discrepancy that I don't understand. Supposedly the request got a 15 byte response? The response should actually be 14 bytes, as can be seen in the other screen capture. The Codesys string display also has the first character missing, and and only shows 13 characters. What is the 21262 number shown for uiLength? All this is extremely confusing.
Please see attached for what I need, how can that be coded with the function block in CodeSys?
Are there any practical examples of how the Ethernet/IP service function blocks are used in PLC programs? https://help.codesys.com/webapp/_cds_obj_function_block;product=codesys;version=3.5.17.0 - this says that "insert with arguments" should show the input and output arguments, but that didn't seem to be happening. The video at https://www.youtube.com/watch?v=-YcEYccH88U shows the visualization, but not the usage. I looked at https://help.codesys.com/webapp/8kboBg6ZzK46zifJPwfAWmWbaa0%2Ffld-Function-Blocks;product=EtherNetIP%20Services;version=3.5.17.0,...
Thanks a lot, that brought up the values. The "Always update variables" at the bottom of the display is confusing, I thought it meant that they would be displayed regardless, didn't know about the separate controls elsewhere. Perhaps this needs to change.
After a lot of experimentation, I am finally able to get the Ethernet/IP link established between the Pi and the device, I am still not sure what exactly was preventing it earlier, have to go back and see whether I can find the issue. Everything is green on the Devices tree, status is good. My question now is about the IO Mapping tab, it shows a grayed out "Not updated" for the Current Value field of all the variables. Do the variables have to be mapped to something in the PLC_PRG for the values...
What does the "Adapter not configured yet ..." diagnostic message mean, along with the "Not running" status of Ethernet/IP? The IP address of the adapter is correct, it has been added by using an EDS file, it can be pinged from the laptop as well as the Pi. What other configuration is expected? These devices work fine with a Rockwell PLC, using the exact same EDS files, and the Class 1 connection gets established right away.
Making progress here, I deleted the Ethernet section and added it again, that added the proper tasks which were missing earlier, I had used the demo program to start with. I did not get the IP address warnings, was able to download and run. Now I have the issue reported in https://forge.codesys.com/forge/talk/Engineering/thread/5efa115498/, but the problem there seemed to be something related to the device not being on, that is not the case here. Please see attached screenshot, would appreciate some...