ZMQ pyleco free example

[seb5g]

Hi @BenediktBurger

I sent you an email about this but can tell also here: some colleagues would like to use Pymodaq with their existing setups that ran with labview. They were thinking about using ZMQ which is just fine with a PyMoDAQ Director.

Could you pinpoint the steps required to build an example from raw ZMQ to interact with the Director?

An example with python but without pyleco would be just fine. Or maybe we can bundle pyleco into a dll to be used within labview?

cheers

[BenediktBurger]

Quick response:

1. You have to create a Labview LECO library (not the Coordinator, but some actor like object)
2. Create the LECO Director in Labview as well

Depending on your use case, it can be sufficient to implement a subaet of these methods.
If they just want to get notifications of New values, and if #405 is implemented, the require Labview implementation will be not that large.

Regarding the implementation, you can take a look at the protocol definiton: https://github.com/pymeasure/leco-protocol/tree/pyleco-state

What is the desired use case?

[seb5g]

They have some labview code already running and while they want to move to pymodaq they are reluctant to transform everything at once. So the idea would be to use one of the pymodaq control module Director and control the instruments they have in labview and get back data into the pymodaq ecosystem!

[BenediktBurger]

I sent you my Private Email, which you might give them for better communication.

Do I understand it correctly, that they want to control a Labview program from a PyMoDAQ dashboard?

One option is to use the existing director plug-ins, that requires, however, to make the Labview Code behave like a pymodaq plugin bring remote Controller, including serialization of pymodaq objects.
Probably, the Labview Code could use the python pymodaq serializer (good that it is it's own package now) for de/serialization.

Another idea: They could write their own pymodaq plug-ins, which then communicate via LECO with the Labview Code.
That would reduce simplify the needed Labview Code.

Now to the Labview code:

• first, there is some work regarding a leco publisher by my collegues: https://git.rwth-aachen.de/nloqo/labview-python-interfaces
• my suggestion is to create a really basic leco library (how to create a leco message and basic json parsing), which should be quite fast
• maybe helper functions like sending a message: it should be a Zmq dealer socket, you use send_multipart message where the different parts are so called frames. For the content see the leco Definition. As a short Intro, the first frame is the leco Version, then Sender, then receiver, then the Header, and finally the payload (either the json message or your own payload between the plugin and the Labview Code)
• for communication with the Coordinator, only very few commands are necessary (could be done even without json parsing!): sending sign_in/out, handle a few errors (if you are not slgned in...) and handle the pong by the Coordinator (could be prevented by sending regularly an empty message to the Coordinator)

I might be able to give a Python example for "pyleco Light", as an idea what to implement in Labview.
I'm open for a call to answer questions and to give hints how to implement leco in Labview.

[seb5g]

Great, thanks for this detailed answer. I will look into it and present this to my colleagues.

[seb5g]

@Ashwolaa you may be interested with this discussion

[malik-irain]

I think there is a big limitation. I could easily do the signin/signout stuff and also use "rpc.discover" to get the callable methods. I can even control an actuator and do an rpc on move_home.

However, if I want to call the move_abs method, I need to give an additional payload which is the serialization of the DataActuator object representing the position I want to go to. I suppose it is the same with any data using units. It means right now, one would have to reimplement DataActuator, its serialization and deserialization in LabView (or any other language) to be able to communicate with an Actor or Director in PyMoDAQ.