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Template Project

The Template project is a minimal, pre-wired TwinCAT application that demonstrates how to connect the ApplicationBase framework into a working starting point. It provides the scaffold — PackMLModule, HMI, recipe loading, and events — all wired and ready to extend.

Entry Point

MAIN.TcPOU instantiates Machine('Machine'), calls Machine.Initialize() on the first scan until initialization completes, then calls Machine.CyclicLogic() every 100 ms.

PROGRAM MAIN
VAR
    Machine : Machine('Machine');
END_VAR

IF NOT Machine.Initialized THEN
    Machine.Initialize();
    RETURN;
END_IF

Machine.CyclicLogic();

Machine Function Block

Machine EXTENDS PackMLModule IMPLEMENTS I_Machine

The top-level function block. It registers all sub-objects in FB_Init and overrides the PackML state methods.

Registered sub-objects:

Object Type Purpose
Events TcEventClass Raises machine-level TwinCAT events
EventReactor EventReactorPackMLVisitor Reacts to events with PackML state transitions
Machine_HMI Machine_HMI HMI symbol and button handling
SyncedSquareWaves SyncedSquareWaves Demo cyclic component
RecipeFile JsonFile<10000> Loads ST_Recipe from C:\Data\Recipe.json

Initialization Sequence

Initializing() runs as a sequenced state machine before the PackML state machine starts:

Step Action
0 Configure Production and Manual unit modes via FB_PMLUnitModeConfig
10 Call RecipeFile.LoadFile()
20 Wait for load to finish, then call RecipeFile.ReadSymbol()
30 Set ModuleInitialized := TRUE

PackML States

Machine extends PackMLModule and overrides the transition methods:

State method Behaviour
Clearing Calls ResetComponents() and ResetModules(), then completes
Starting Completes immediately
Execute Empty — add production logic here
Stopping Completes immediately
Aborting Completes immediately
Stopped, Aborted No override

Unit modes configured: Production, Manual. Both allow mode changes from Stopped and Aborted states.

Cyclic Logic

OnCyclicCall() runs every scan inside CyclicLogic():

  • Manual mode — HmiEnableDisableAllVisitor enables HMI on every node in the tree, allowing individual component control from the HMI.
  • All other modes — HMI is disabled on the tree; only the top-level Machine_HMI is re-enabled.
  • SetAllOverrideVisitor propagates _Override to every component in the hierarchy each scan.
  • Raises E_Machine.EStop_Pressed when the E-stop is not OK.

HMI

Machine_HMI EXTENDS PackMLStatemachine_HMI

Handles the three standard operator buttons and writes the HMI struct to the TwinCAT HMI symbol server.

Button Permissive Action
Start Current state = Stopped ChangeState(Start)
Stop Current state ≠ Aborted ChangeState(Stop) (or Abort when already Stopped)
Reset Current state = Aborted ChangeState(Clear) (or Reset otherwise)

The ST_Machine_HMI struct is published as a TwinCAT HMI symbol (accessible to Administrators and Admin group):

TYPE ST_Machine_HMI EXTENDS ST_HmiFunction :
    STRUCT
        Override : LREAL := 100.0;
    END_STRUCT
END_TYPE

Interface

I_Machine EXTENDS I_ContainStatemachine

Member Type Direction Purpose
Override LREAL set Speed / override percentage applied to all components
Recipe REFERENCE TO ST_Recipe get Active recipe values

Recipe

ST_Recipe is loaded from C:\Data\Recipe.json at startup and re-read into the symbol Recipe via the ADS symbol interface.

ST_Recipe
└── Axis : ST_AxisRecipe
    ├── Velocity     : LREAL := 100
    ├── Acceleration : LREAL := 1000
    ├── Deceleration : LREAL := 1000
    └── Jerk         : LREAL := 1000

Extending the Template

To build a real application from this template:

  1. Add components and sub-modules — declare them inside Machine and register them in FB_Init with RegisterWithParent(THIS^).
  2. Implement state logic — fill in the Starting, Execute, Stopping, and Clearing methods with the production sequence.
  3. Extend the recipe — add fields to ST_Recipe and update C:\Data\Recipe.json accordingly.
  4. Add events — define event enums in the .tmc event class file and raise them via Events.RaiseEvent(...).
  5. Extend the HMI — add fields to ST_Machine_HMI and handle them in Machine_HMI.CyclicLogic().