Pylogix Local UDT

Taylor Turner · Oct 4, 2022

Can I not access locally defined UDT data?

Scope..
Task>Prog1>Parameters and Local Tags(Test1 = real)(UTD.Test2 = real)

Code:

#To access the local tag.. (Works)
$PLC.Read('Program:Prog1.Test1').Value


#To access the UDT tag.. (Does not work)
$PLC.Read('Program:Prog1.UDT.Test2').Value

dmroeder · Oct 4, 2022

What does "does not work" mean? What does it say when you print .Status?

Taylor Turner · Oct 4, 2022

"Program not found, please check name!"

dmroeder · Oct 4, 2022

Taylor Turner said:
"Program not found, please check name!"

I have checked the name(s)

That appears to be a response from "GetProgramTagList()", not a read.

Edit: So somewhere you are calling GetProgramTagList("Program Name") and it is not finding that program name.

Taylor Turner · Oct 4, 2022

I regret to inform... I found a syntactic error in my own regard.

dmroeder · Oct 4, 2022

Taylor Turner said:
I regret to inform... I found a syntactic error in my own regard.

I'm actually happy that was the case

Taylor Turner · Oct 4, 2022

dmroeder said:
That appears to be a response from "GetProgramTagList()", not a read.

Edit: So somewhere you are calling GetProgramTagList("Program Name") and it is not finding that program name.

Thanks a ton...

Stat info: My program runs ~180ms faster by reading the tags as a dictionary. (09_multi_read_faster.py)

dmroeder · Oct 4, 2022

Taylor Turner said:
Thanks a ton...

Stat info: My program runs ~180ms faster by reading the tags as a dictionary. (09_multi_read_faster.py)

Yes, lists are much faster because multiple reads are packed into a single packet, where if you call Read one at a time, they each get their own packet. I have a couple of new things to hopefully further increase performance, it's just a matter of finding the time.

Taylor Turner · Oct 5, 2022

dmroeder said:
Yes, lists are much faster because multiple reads are packed into a single packet, where if you call Read one at a time, they each get their own packet. I have a couple of new things to hopefully further increase performance, it's just a matter of finding the time.

Another note:

I have an application using Pylogix as middleware amung three devices. This application uses the asyncio, transports and Protocol module to talk to one of the devices(not the PLC). The data_received runs when there is a change for me. I'm working a second project where I need to observe tag changes from the PLC. I don't want to poll pylogix constantly, are there any alternatives you can think of? Currently looking into a MSG instruction and PyDispatcher.

dmroeder · Oct 5, 2022

Taylor Turner said:
Another note:

I have an application using Pylogix as middleware amung three devices. This application uses the asyncio, transports and Protocol module to talk to one of the devices(not the PLC). The data_received runs when there is a change for me. I'm working a second project where I need to observe tag changes from the PLC. I don't want to poll pylogix constantly, are there any alternatives you can think of? Currently looking into a MSG instruction and PyDispatcher.

Pylogix doesn't have a "listen" function, thought that is an interesting idea, a few people have asked for over the years.

What is your concern with constantly polling the tag? How frequently would you be polling it?

Taylor Turner · Oct 5, 2022

dmroeder said:
Yes, lists are much faster because multiple reads are packed into a single packet, where if you call Read one at a time, they each get their own packet. I have a couple of new things to hopefully further increase performance, it's just a matter of finding the time.

dmroeder said:
Pylogix doesn't have a "listen" function, thought that is an interesting idea, a few people have asked for over the years.

What is your concern with constantly polling the tag? How frequently would you be polling it?

Ideally a script would run only when the plc tells it to. I have yet to test the performance by polling, your 06_read_loop.py. My only concern right now is in theory. Polling hogs a thread and voids RTOS principals, eventually I need to account for a battery powered system. I'll code it up and get an application point of view though.

Pylogix Local UDT

Taylor Turner

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dmroeder

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Taylor Turner

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dmroeder

Lifetime Supporting Member

Taylor Turner

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dmroeder

Lifetime Supporting Member

Taylor Turner

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dmroeder

Lifetime Supporting Member

Taylor Turner

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dmroeder

Lifetime Supporting Member

Taylor Turner

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