Configuring Automatic User Login on SIMATIC Basic Panels (TIA

Overview

This article documents how to implement an automatic operator login at runtime start on SIMATIC Basic Panels (KTP400 Basic, KTP700 Basic, KTP700 Basic 2nd generation, KTP900 Basic, KTP1200 Basic, KTP1200 Basic 2nd generation) programmed with TIA Portal / WinCC (TIA Portal) Comfort or Advanced. Automatic login is commonly requested when an HMI must power up directly into the operator's main screen without presenting a password dialog, for example on OEM starter kits, kiosk-style HMIs, or single-role machines.

Three engineering approaches are presented:

1. Dummy start screen + value-change event using the system function Logon.
2. Area pointer "Coordination" + tag trigger firing the Logon function on tag change.
3. Scheduler / planned task calling Logon once at runtime start (supported only on Comfort Panels and on Basic Panels whose runtime image supports scheduled tasks - see compatibility section).

Prerequisites

User Administration on Basic Panels

User administration in TIA Portal is configured under Runtime settings > User administration of the HMI device. Each panel supports a limited number of users and groups; the limits differ between 1st and 2nd generation devices:

Create at least one group (e.g., "Operators") with appropriate area authorizations and assign at least one user (e.g., "Operator") to that group. The login used for the automatic procedure must exist with a known, project-defined password - never rely on default empty passwords because they are stripped at compile time.

Confirm the user can be logged in manually from the runtime via the standard user button before automating the procedure. This isolates credential problems from automation problems.

System Function Reference

The TIA Portal Logon system function logs the named user on with the supplied password. Its parameters:

Two complementary functions are useful for cleanup:

• Logoff - terminates the current user session.
• GetUserName - reads the currently logged-in user into a string tag for diagnostics.

Detailed parameter semantics are in the WinCC (TIA Portal) system manual referenced in the Prerequisites table. The Logon function executes synchronously on the HMI runtime; no screen change is performed by the function itself.

Approach 1 - Dummy Start Screen with Value-Change Event

This is the most widely supported method on legacy and current Basic Panels because it uses only screen events and the built-in Logon function - no scripting, no scheduler, no project-wide event needed.

Concept: Configure the panel's startup screen to a dedicated, empty "AutoLogin" screen that contains an internal trigger tag. When the screen loads, the tag's start value triggers a value-change event that runs the Logon function with hard-coded credentials and then activates the real start screen.

Step-by-step - Approach 1

1. In the HMI tag table create an internal tag HMI_StartupTrigger of type Bool with Start value = 1.
2. Add a new screen AutoLogin. Leave the visual content empty (optional text "Logging in...").
3. In the project tree, under HMI device > Screens > AutoLogin > Events, open Loaded.
4. Add the following function list on the Loaded event:
   1. Set tag - set HMI_StartupTrigger = 0 (to avoid re-trigger on screen refresh).
   2. Logon - User = "Operator", Password = the operator's password constant.
   3. Optionally: Set tag - write return value of Logon into a diagnostic tag HMI_AutoLoginResult.
   4. ActivateScreen - Screen name = "Main", Number = configured screen number (default 1).
5. In the value-change event of HMI_StartupTrigger add a redundant ActivateScreen calling the main screen as a safety net.
6. Open Runtime settings > General > Start screen and select AutoLogin as the project's start screen.
7. Compile and download the project to the panel.

Why it works: The screen's Loaded event fires exactly once per runtime start because the trigger tag is reset to 0 inside the same function list. Manual operator navigation back to AutoLogin after first start will still reset the trigger, but the value-change event will not fire (0 -> 0) and the user will simply be re-validated, which is harmless.

Approach 2 - Area Pointer Coordination with Tag Trigger

The Coordination area pointer is a 1-word interface that lets the PLC handshake with the HMI for life-bit and operator acknowledgement. It also exposes the runtime's "operating state" via individual bits. By assigning a tag of the PLC's choosing as the trigger source, you can fire Logon from a value-change event anywhere in the project without relying on a dedicated screen.

Step-by-step - Approach 2

1. Enable the Coordination area pointer under Runtime settings > Connections > Area pointer with a tag from the PLC (e.g., DB_HMI.Coordination, length = 1 word).
2. Create a trigger tag HMI_LoginPulse of type Bool, Start value = 0, internal.
3. Open HMI device > Events > Tag value changes and add an event for HMI_LoginPulse on the change from 0 to 1.
4. Add to that event:
   1. Set tag - HMI_LoginPulse = 0 (clear the pulse).
   2. Logon - User = "Operator", Password = operator password.
   3. ActivateScreen - "Main".
5. From the PLC startup OB (e.g., OB100) or first scan, set the HMI bit that drives HMI_LoginPulse to 1 for one cycle after the HMI signals "ready". A common pattern:

// Pseudo-ST in PLC startup
IF "HMI_Coord".%X11 THEN // bit "ReadyForOperation" from Coordination pointer
  "HMI_LoginPulse" := TRUE;
END_IF;

Why it works: The Coordination area pointer tells the PLC when the HMI runtime is fully initialized. Driving HMI_LoginPulse from the PLC ensures that the value-change event fires after the HMI user administration is loaded - which is required for Logon to find the user entry.

Approach 3 - Scheduler (Where Supported)

Some Basic Panel images support the Scheduler (planned tasks) editor under HMI device > Schedules. Where supported, you can configure a one-shot task that fires Logon at runtime start.

1. Open HMI device > Schedules and add a new trigger named AutoLogin.
2. Set the trigger condition to "Runtime start" (available on Comfort Panel images and selected 2nd gen Basic Panel images).
3. Configure the event to call the Logon system function with the operator credentials.
4. Optionally follow with ActivateScreen to your main screen.

Parameter Mapping Summary

Verification

1. Reboot the panel (power-cycle, do not just restart the runtime from the loader).
2. Observe: the panel briefly shows the AutoLogin screen (Approach 1) or the configured main screen directly (Approach 2 / 3).
3. Open the user button on the runtime and confirm that the current user is the configured operator, not "Logged out".
4. Inspect the diagnostic tag HMI_AutoLoginResult - it must contain 1 (TRUE) after startup. If it reads 0 the Logon call rejected the credentials; jump to the Troubleshooting section.
5. Stop and restart the HMI runtime from the loader (Start > Start Runtime) three times and verify identical behavior.
6. Power-cycle the panel and verify again. The trigger must fire on every cold start.

Troubleshooting Matrix

Security Considerations and Field-Proven Caveats

• Credentials compiled into the HMI runtime file are extractable from the .ap* / .br* image. Do not reuse the same password for operator accounts on HMIs that ship into unsecured environments.
• On 2nd generation KTP Basic panels, user passwords are hashed in the project but the plaintext is still compiled into the runtime; treat the compiled runtime as confidential.
• If you need an "automatic" feel without hard-coded credentials, configure a button that calls Logon with credentials from a tag, and have the operator authenticate via RFID or barcode reader that writes the tag. This decouples the credential from the project file.
• Adding automatic login disables the original "User view" logon dialog for the operator role. Always provide a path (e.g., shift change button) that calls Logoff before allowing a different role to log in.
• Combine with the User login required for operation option in the screen's security settings if you want all other screens to remain protected by group membership while still bypassing the logon dialog.

Field Commissioning Notes

• Always validate the procedure on the actual target panel, not only the TIA Portal simulation. The PC simulation may handle screen Loaded events differently than the embedded runtime.
• If the panel is part of a larger HMI network with a master panel, configure the operator credentials identically on every panel to avoid mismatches after master-to-slave tag distribution.
• For migration from WinCC flexible projects: the same Logon system function exists; the dummy-screen pattern translates directly to TIA Portal screens without changes.
• On KTP1200 Basic 2nd generation panels, the runtime supports up to 50 users; reserve at least one slot for a "ServiceAutoLogin" account used only during commissioning and disable that user at production handoff.