Using custom UDTs with code generation

Overview

PLCflow includes system UDTs (UDT_MotorSimple, UDT_MotorVFD, UDT_ValveDiscrete, UDT_ValveAnalog, UDT_SensorAnalog, UDT_Setpoint, ALARM_UDT) that work out of the box. These are reasonable defaults but rarely match an established shop’s existing standards. The way to bridge that gap is to add your own UDTs to the library and have the generators use them instead.

This recipe covers the full workflow: get your UDT into the library, bind its members to the generator slots, use it in a generation, import the result. Once a UDT is in the library, every subsequent project on the same account can reference it.

Use this recipe when your shop has standard UDTs you want PLCflow to generate against, when a customer requires their own UDT structure for delivery, or when the system defaults are close to what you need but missing a specific member.

Step 1. Add your UDT to the library

Open UDT Library from the dashboard. Two ways to get your UDT in.

Option A. Upload from L5X

If your UDT already exists in a Studio 5000 project, this is the fast path.

1. In Studio 5000, right-click the UDT in the Data Types folder, click Export Component. Save the L5X to disk.
2. In UDT Library, click Upload UDT in the top-right.
3. Drop the .L5X file in the dialog (or click to browse).
4. Set the Category for the UDT. This is the critical step. The category determines which generation module sees this UDT. Valid categories:
   • MOTOR, VFD_MOTOR for fixed-speed and variable-speed motors
   • VALVE for on/off valves
   • AI, AO for analog inputs and outputs
   • DI, DO for discrete I/O (rarely customized; the defaults usually fit)
   • ALARM for Alarm Code’s alarm structures
   • PARAMETER for Parameter Code’s setpoint structures
5. Optionally set a Name Override to rename the UDT during import.
6. Click Upload. The UDT lands in your User-scope library.

Option B. Build manually in the editor

If you want to build from scratch (no existing L5X):

1. Click New UDT in the top-right of UDT Library.
2. Fill in the Name (must be unique in your scope), Category, and Description.
3. In the All Members panel, click Add Member for each member: name, data type, default, description, required flag.
4. Bind members to the Required Fields generator slots that show up for the selected category (see Step 2 below).
5. Click Create UDT.

Either way, the UDT now lives in your User-scope library and is visible to every PLCflow project on your account.

Step 2. Bind members to the generator slots

This is where most “I added my UDT but the generation does not work” issues come from. Each category has a set of generator slots the modules need filled. For example, a MOTOR-category UDT needs members bound to the “run command”, “run feedback”, and “fault” roles. The names of your members can be anything (Run_Cmd or Cmd_Start or Drive_Enable), but the binding tells PLCflow which one to drive.

The edit dialog has a Required Fields panel that lists every slot for the chosen category. Each row:

• An orange marker for required slots, grey for optional ones.
• The slot’s purpose (the human-readable role).
• A small chip showing the role identifier.
• A dropdown to pick which of your members fills that slot.

Pick a member from the dropdown for each required slot. The dialog blocks save until every required slot is bound and surfaces a message naming the unfilled slot.

Members not bound to any slot are kept as internal. They become part of the UDT’s structure and ship in the generated L5X, but the generator doesn’t drive them. Useful for HMI-only fields, timestamps, operator IDs, and other metadata.

Step 3. Use the UDT in the generation editor

Open the target generation module (I/O Code, Alarm Code, or Parameter Code) and either upload a spreadsheet or add rows manually.

Each row has a UDT column with a dropdown showing every UDT in the library that matches the row’s category:

• In I/O Code, the dropdown filters by device type (MOTOR rows show MOTOR UDTs, VALVE rows show VALVE UDTs, etc.).
• In Alarm Code, the dropdown shows ALARM UDTs.
• In Parameter Code, the dropdown shows PARAMETER UDTs.

Pick your custom UDT in the UDT column for any row that should use it. The generated L5X references that UDT by name; the AOI calls resolve member references based on which member is bound to each slot in the UDT definition.

If you have an existing Tag Database populated under the matching category, Import from DB pulls those rows in with the UDT reference already set.

Step 4. Generate and import

From the populated editor:

1. Click Validate to confirm every row passes, including that the UDT reference resolves to a library entry with all required slots bound.
2. Click Generate Code. The console streams progress.
3. The generated L5X references your custom UDT by name throughout. The Required Components panel includes the UDT L5X for import into Studio 5000.

Studio 5000 import

If your custom UDT already exists in your Studio 5000 project (you exported it from there in Step 1), Studio 5000’s import dialog defaults to Use Existing. No collision, no extra import needed.

If your custom UDT does not yet exist in the target project (you built it in PLCflow):

1. Right-click the Data Types folder.
2. Click Import Component.
3. Select the UDT L5X from PLCflow’s Required Components.
4. Click OK.

Then import the main routine:

1. Right-click the program you want the routine in.
2. Click Import then Import Routine.
3. Select the routine L5X.
4. Set the routine name if prompted.
5. Click OK.
6. Review your code before deployment. Walk through a few rungs; confirm they reference your custom UDT.

Common pitfalls

FAQ

What if my UDT has Studio 5000-specific features like initial values?

The L5X upload preserves member metadata, including default values on members. When you save defaults on a member in the editor, those flow through to the generated L5X. Round-trip is preserved.

Can I share custom UDTs across team members?

User-scope UDTs are visible only to the user who created them. Project-scope UDTs (visible to everyone on a project) ship with the Projects module. Org-wide libraries are on the roadmap. In the meantime, export the UDT to L5X and have each team member upload it.

How do I know what slots PLCflow expects for a specific category?

Open the matching system UDT in UDT Library and look at its Required Fields panel. That shows every slot the category supports, marked required vs optional. Build your custom UDT to fill the same slots.

Can I have multiple variants of the same UDT (T_MOTOR_v1, T_MOTOR_v2)?

Yes. Each is a separate library entry under a different name. Different generations can use different variants. Useful when migrating a fleet of projects from one structure to another.

My custom UDT works for some rows but not others. Why?

Most often the UDT category doesn’t match the row’s type. The dropdown only shows UDTs that match. If a row falls back to the default unexpectedly, double-check the UDT’s category against the row’s device type.

Related

• UDT Library. Where the custom UDTs live and where the slot-binding happens.
• I/O Code, Alarm Code, Parameter Code. The three primary consumers of custom UDTs.
• Tag Database. Tags carry the UDT reference. After setting up custom UDTs, populate the Tag Database to lock in shop-wide naming.