What the window is telling you
EasyBuilder Pro polls every device configured in the project. When one stops answering, the runtime pops the "PLC no response" window with the device name, station number and a code identifying the failed conversation — and repeats it on every retry, which is why the screen fills with the same message. The useful information is which device and station: that's the conversation to debug, not the HMI, not the whole network.
Six checks, in order
| Check | Where | Classic miss |
|---|---|---|
| 1 · Right driver for the PLC | System Parameters → Device list in EasyBuilder Pro | The protocol variant matters — the wrong flavor of the right brand still times out |
| 2 · Station number / unit ID | Device settings on both ends | HMI polling station 1 while the PLC answers as station 2; on multi-drop RS-485, duplicate stations |
| 3 · Serial parameters match exactly | Baud, data bits, parity, stop bits | Delta DVP-style defaults (9600, 7, E, 1, ASCII) vs the driver's RTU default — one wrong field is enough |
| 4 · Wiring | RS-485 A/B lines, shield, terminators | A/B swapped works on the bench with one device and fails on the machine |
| 5 · Tags pointing at addresses the PLC doesn't have | The objects on the screens where the error pops | The window appears only on certain screens → an object there polls a register that doesn't exist in this PLC |
| 6 · EasyBuilder Pro version | Project compiled on an old EBPro | Documented driver bugs fixed by minor updates (e.g. a 4.10.04 → 4.10.06 Modbus RTU fix) — recompile on current |
When a device is gone for good
If the window points at a device that was physically removed from the machine, the fix is configuration hygiene, not comms: delete it from the device list (or disable its polling) and re-download the project. Leaving ghosts configured buries real errors under noise.
Screen dark instead of erroring?
That's a different tree — power, backlight, boot — covered in the black-screen triage. And if the question is whether the HMI or the PLC is at fault, the brand-agnostic checklist settles it in a minute.
Keep producing while you wait
Have the panel project export? Drop a FactoryTalk View, TIA Portal, Weintek or CSV export into our free HMI project converter — it runs in your browser, the file never leaves your PC, and every display becomes a page of buttons, indicators and values for the app, with the real tag names already in place.
Today, from a phone: the free LineKeeper app for iPhone and iPad speaks EtherNet/IP, Siemens S7 and Modbus TCP. On Allen-Bradley Logix it reads the controller's own tag list automatically; on S7 and Modbus you add the addresses you care about. Build a dashboard and an operator panel with start/stop buttons in about 15 minutes, mount a spare iPad in full-screen panel mode, and the operator has a screen before the first repair quote arrives. Reading is free; writes are a one-time unlock with confirmation and limit checks on every value.
The 15-minute temporary panel
Zero-config tag browser for Logix, drag-and-drop dashboard, operator panel, alarms — no changes to the PLC program.
On a desktop? Scan with your iPhone or iPad to get the free app.For the machine itself: the LineKeeper device — in development — is a self-contained 7″ or 10″ touchscreen built to live on the machine permanently — the same drag-and-drop screens, plus what a phone shouldn't carry:
- Live view of every tag, refreshed twice a second — plus write access with a full audit log
- Operator panel: start/stop, indicators, setpoints — hold-to-run buttons release safely
- Stays useful after the repair: data logging, dashboards, machine diagnostics
Small hardware that helps while the panel is out
- GL.iNet Opal travel router — Wi-Fi into the machine network from a spare switch port, so the phone app can stand in as the screen today.
- Anker USB-C to gigabit Ethernet adapter — wired straight into a spare switch port, the phone sees the controller in seconds; USB-C iPhones and iPads need no drivers.
- VIVO pole-mount VESA arm — puts the temporary screen at eye level on a machine post instead of a chair.
- TICONN IP67 enclosure with clear cover — houses the gateway or Wi-Fi bridge on the machine without bare boards on the rail.
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