Adding a simulation¶

A simulation is two classes: a model (the physics, no UI) and a view (the drawing).

The model¶

plcyard/sims/my_machine.py. Its module docstring documents the I/O: it becomes the simulation reference.

"""Conveyor with a photo-eye.

Digital (slot words):
  %I0.0 Start (NO)   %I0.1 Stop (NC)   %I0.2 Photo-eye
  %Q0.0 Motor
"""

@dataclass
class ConveyorModel:
    name = "Conveyor"
    position: float = 0.0
    start_pressed: bool = False
    stop_pressed: bool = False
    outputs: int = 0
    events: list[str] = field(default_factory=list)

    def input_words(self) -> dict[int, int]:          # slot → 16-bit word, read every input scan
        return {1: int(self.start_pressed) | int(not self.stop_pressed) << 1}

    def set_output_words(self, words: dict[int, int]) -> None:   # written every output scan
        self.outputs = words.get(2, 0) & 0xFFFF

    def step(self, dt_ms: float) -> None:              # advance the physics after each scan
        ...

• Slot 1 is %I0.x, slot 2 is %Q0.x.
• Analog: analog_inputs() returns {channel: volts} (0-10 V, channel 0 is %IW64); set_analog_outputs(volts) receives the outputs.
• Append a line to events for misuse (a crash, an overflow).

Register it in MODELS in plcyard/sims/__init__.py: "conveyor": ("Conveyor", ConveyorModel).

The view¶

A QWidget that takes the model and repaints it (see plcyard/ui/sim_views3.py for examples built on the shared canvas and control panel), registered in VIEWS. Give every labelled device its address so it can be dragged onto a program.

The example and the tests¶

Add a working example in plcyard/data/samples/ and a test that runs it on the model and checks the machine does its job. Then regenerate the reference:

python -m plcyard.docgen