Resolving Sm@rtClient App No Input Gray Screen on TP900 Comfort

Problem Description

The Siemens Sm@rtClient App (iOS) connects to a SIMATIC HMI Comfort Panel running the integrated Sm@rtServer runtime option and mirrors the panel screen on an iPhone or iPad. After deploying a TP900 Comfort panel in February 2017 for remote access, the customer reported that starting around October 2017 the Sm@rtClient session opens to a flat gray canvas with a "No Input" icon. The behavior reproduces on a previously working iPhone (iOS 11.2.2) but does not reproduce on a control iPhone running iOS 10.1.2 with Sm@rtClient Lite. A hard reset of the iOS device and a network-settings reset do not clear the fault.

The same diagnostic icon ("No Input") is used in WinCC Comfort/Advanced runtime to indicate that a configured tag, area pointer, or connection does not have a valid value. The visual effect on a remote Sm@rtClient is a uniform gray backdrop because the panel cannot paint any tag-bound object without that data source. The fault is therefore not a smartphone rendering bug in isolation; it is a runtime-state symptom whose cause can sit in the panel, the network path, the TIA Portal project, or the mobile app build.

Affected Environment

Root Cause Analysis

Three root-cause classes converge on the same "No Input" surface symptom. Investigate them in this order because each one is faster to rule out than the next.

Cause A — Mobile app regression on iOS 11.x

Sm@rtClient versions prior to V1.1.2 ship an internal session-establishment routine that breaks under iOS 11.2+. The session starts, the gray canvas is drawn, and the runtime reports "No Input" because the tag-stream back-channel is never initialized. The fix in V1.1.2 is a client-side patch; the panel-side runtime is unchanged.

Evidence: the same panel image, served to a Sm@rtClient Lite client on iOS 10.1.2 and iOS 11.2.1, paints correctly. Only the full Sm@rtClient build on iOS 11.2.x is broken, which isolates the fault to the app/iOS interaction.

Cause B — Project-side Visibility animation misuse

A TIA Portal project that sets a Visibility animation on the entire main screen (the root screen object) rather than on a contained element evaluates the visibility tag at session start. If the tag is uninitialized when the Sm@rtClient session establishes, the screen is rendered invisible — which displays as a flat gray with no objects. This is one of the documented anti-patterns in the WinCC Comfort scripting manual.

The bug is silent in TIA Portal compile: the project downloads, the local panel boots, but on first paint the root screen has visibility = 0. From a remote client the diagnosis reads as "No Input" because the runtime cannot resolve any of the screen's bound tags.

Cause C — Sm@rtServer session state, certificate, or authentication

If Sm@rtServer is not started on the panel, the Sm@rtClient cannot complete the handshake and the canvas is drawn empty. The same effect appears when:

• The panel's user authentication rejects the Sm@rtClient credential set.
• The Sm@rtServer certificate changed (panel clock reset, certificate renewal) and the client caches the previous fingerprint.
• The Sm@rtServer port (default 443 for HTTPS-based Sm@rtServer; legacy 1024/5900/5800 for VNC-style Sm@rtServer) is blocked by a firewall or NAT rule.
• The HMI image was reloaded without re-enabling the Sm@rtServer runtime option.

Diagnostic Procedure

Run the following checks in order. Each check has a pass/fail criterion and a fixed next step.

Step 1 — Confirm the local panel screen

1. Walk up to the TP900 Comfort and observe the local display for the same screen the customer is trying to view.
2. If the local display is correct and only the remote client shows gray + "No Input", go to Step 2.
3. If the local display is also gray with "No Input", the fault is upstream of Sm@rtServer — open the TIA Portal project, check tag connections, then go to Step 5.

Step 2 — Verify the Sm@rtClient app build

1. On the iPhone, open the App Store → Updates → confirm the installed Sm@rtClient version.
2. Target build: V1.1.2 or later. Builds prior to V1.1.2 are not reliable on iOS 11.2.x.
3. If the installed build is below V1.1.2, update and re-test before doing anything else.

Step 3 — Verify Sm@rtServer state on the panel

1. On the TP900 Comfort, open the Control Panel → "Sm@rtServer" (or "System").
2. Confirm Sm@rtServer is set to Start and the configured port matches the value entered in the Sm@rtClient session.
3. Confirm a password is set and that the same password is entered on the client.
4. If the panel was re-imaged or a new runtime image was downloaded, Sm@rtServer defaults to disabled. Re-enable and re-enter the password.

Step 4 — Verify network reachability

1. From the iPhone (on the same network as a local test, or on a network that has a route to the panel), open Safari and browse to https://<panel-ip>:<port>.
2. A successful TLS handshake that returns the Siemens Sm@rtServer landing page confirms the port and certificate are reachable.
3. If the browser reports a certificate warning, accept it once on the iPhone and then re-launch the Sm@rtClient so the new fingerprint is cached.

Step 5 — Inspect the TIA Portal project for the visibility-on-root-screen anti-pattern

1. Open the project in TIA Portal and navigate to the affected screen.
2. Select the root screen object (the screen itself, not a contained control).
3. Open Properties → Animations → Visibility. If a tag is bound to the root screen's Visibility, the binding must be removed or moved to a child object.
4. Recompile, download to the panel (full download, not delta), and re-test.

Resolution Procedures

Resolution 1 — Update Sm@rtClient to V1.1.2 (primary fix)

1. On the affected iPhone, launch the App Store.
2. Tap the profile icon, swipe down to refresh, and install any pending Sm@rtClient update.
3. Confirm the installed version reads 1.1.2 (or later) under Sm@rtClient → Settings → About.
4. Force-quit the Sm@rtClient app and re-launch.
5. Re-enter the panel IP, port, and password and start the session.

Expected result: the TP900 Comfort screen paints within 3–8 seconds and tag values update live. The "No Input" icon does not appear.

Resolution 2 — Remove visibility animation from the root screen

1. In TIA Portal, open the screen that displays gray on the remote client.
2. Click the empty area outside any control to select the root screen object.
3. Open Properties → Animations and delete any Visibility entry.
4. Apply the same animation to a transparent overlay rectangle or a placeholder element if the logic is genuinely required.
5. Compile the project (full rebuild) and perform a full HMI image download to the TP900.
6. Cycle power on the panel and re-test from the iPhone.

Resolution 3 — Re-establish the Sm@rtServer session

1. On the TP900 Comfort Control Panel, open the Sm@rtServer settings.
2. Toggle Sm@rtServer Stop, wait 10 seconds, then toggle Start.
3. If a password is set, change it to a temporary value, save, then change it back. This forces the Sm@rtClient to re-authenticate from scratch.
4. On the iPhone, delete the saved session in the Sm@rtClient app and re-enter the connection parameters.

Resolution 4 — Reset the Sm@rtServer certificate

1. On the TP900 Comfort, open Control Panel → Security → Certificates.
2. Delete the active Sm@rtServer certificate and let the runtime regenerate one.
3. From the iPhone, browse to the panel's Sm@rtServer URL in Safari once to accept the new certificate.
4. Re-launch the Sm@rtClient session.

Verification

After applying the fix, run the following checks to confirm the fault is cleared.

Preventive Configuration

Two project-level practices reduce the chance of recurrence for the next service visit.

1. Never bind Visibility to the root screen object. Use a contained, transparent placeholder element and bind Visibility to that element. This keeps the root screen always visible and isolates the conditional logic.
2. Document the Sm@rtServer port and password in the project documentation. After every TIA Portal download, confirm the Sm@rtServer toggle is still enabled. A common cause of a previously working panel losing remote access is a re-image that reset the runtime option to disabled.

Escalation Path

If the above steps do not clear the "No Input" symptom, collect the following artifacts and escalate to Siemens Industry Online Support:

• TIA Portal project archive (with the runtime image export)
• TP900 Comfort firmware / image version (read from the Control Panel → System → About)
• Sm@rtClient app version (from iPhone App Store)
• iOS version and device model
• A short video or screenshots of the local panel vs. the remote client, side by side, showing the same screen at the same time
• Network topology (panel IP, port, NAT/firewall rules in the path)

Submit through the Siemens Industry Online Support portal with the order number and the panel's serial number for a faster trace against known Knowledge Base entries.

Cross-Reference: "No Input" in Industrial HMI Context

The "No Input" / "No Signal" surface icon is a common diagnostic across industrial HMI families. It is not specific to Siemens or to Sm@rtClient:

• PanelView Standard operator terminals render a similar diagnostic when zero I/O words are configured (Words Sent = 0 in the message configuration), as documented in the PanelView Standard Operator Terminals User Manual (2711-UM014).
• Projector and monitor families (Panasonic PT-RZ970, Dell E2014H) reserve a "No Input Signal" canvas for the same root cause class — a configured source that is not producing a valid signal. See the Panasonic PT-RZ970 Operating Instructions and the Dell E2014H User's Guide for the equivalent fault tree.

Pattern: if a device renders a flat background plus a "no input" indicator, the diagnostic always points at a missing or invalid source upstream, not at the renderer. The same principle applies to Sm@rtClient and the TP900 Comfort.

Field Notes

• iOS 11 changed the URLSession default timeout and TLS behavior; that is the most likely cause of the regression. Building the mobile app against the new iOS 11 transport stack (V1.1.2) is the supported workaround.
• Sm@rtClient Lite uses a different code path and is not a reliable regression test for the full Sm@rtClient. If a customer reports a fault, ask which app they are using — it changes the answer.
• A gray remote client is rarely a display problem. Spend the diagnostic budget on the project, the runtime option, and the app build before suspecting the iPhone hardware.