HMI — Human-Machine Interface¶

PiPLC includes a built-in HMI editor for creating interactive operator panels that bind directly to PLC memory.

Modes of Operation¶

Mode	Launch	Description
Embedded	Tools > HMI	HMI window inside the main IDE
Standalone	`PiPLC-HMI` executable	Independent app that connects to any engine via WebSocket

Standalone HMI Application¶

The standalone PiPLC-HMI application connects to any PiPLC engine on the network, making it ideal for dedicated operator stations or remote monitoring.

Launching:

# Open with connection dialog
piplc-hmi

# Connect directly to a server
piplc-hmi --url ws://192.168.1.50:9100

# Open a saved HMI project file
piplc-hmi --file my-panel.hmi

Connection menu (standalone mode only):

Connect to Server (++ctrl+shift+c++) — opens a connection dialog to enter the server URL and select a context
Disconnect — disconnects from the remote engine

The status bar shows connection state (Connected/Disconnected) in standalone mode.

Tip

On Windows, .hmi files are associated with PiPLC-HMI during installation. Double-click any .hmi file to open it directly in the standalone app.

Editor and Runtime Modes¶

The HMI window has two distinct modes:

Editor Mode¶

The full editing environment with all chrome visible:

Menu bar, main toolbar, element palette, and properties panel
Drag and drop elements from the palette onto the canvas
Configure element properties (address bindings, colors, labels, ranges)
File operations: New, Open, Save, Save As

Runtime Mode¶

A minimal interface focused on the live operator panel:

Menu bar and main toolbar are hidden
Only a minimal runtime toolbar with mode toggle buttons is shown
Element palette and properties panel are hidden
Window auto-resizes to match the canvas resolution
Live data binding refreshes at 20 Hz (50 ms interval)
Scan statistics displayed in the status bar (scan count and average time)

Switch between modes using:

Mode > Editor Mode or ++f5++
Mode > Runtime Mode or ++f6++

Program change safety

If a program download replaces the monitored context's program while in runtime mode, the HMI automatically returns to editor mode to prevent stale bindings from referencing deleted data. A status bar message notifies you: "Program changed — HMI returned to editor mode."

Context Selection¶

By default, the HMI follows the IDE's active engine context. You can override this to monitor a different context independently:

Follow IDE checkbox (toolbar) — when checked, the HMI tracks whatever context the IDE has selected
Uncheck Follow IDE to enable the context combo box
Select any available engine context from the dropdown
The combo box updates automatically when contexts are created, removed, or renamed

This allows you to edit one context in the IDE while monitoring a different context on the HMI.

Note

If the pinned context is removed, the HMI falls back to the IDE's active context.

Fullscreen Kiosk Mode¶

Press ++f11++ to enter fullscreen mode, which hides all chrome — menu bar, toolbars, status bar, and dock panels — leaving only the HMI canvas.

Press ++f11++ or ++escape++ to exit fullscreen
++alt+f4++ in fullscreen exits fullscreen instead of closing the application
Dock panels are restored appropriately based on the current mode (editor or runtime)

This is ideal for dedicated kiosk-style operator stations using a Raspberry Pi touchscreen.

Canvas Configuration¶

Resolution Outline¶

A dashed rectangle shows the target screen resolution as a design guide.

Toggle via View > Show Resolution Outline (enabled by default)
A resolution label is displayed at the bottom-right corner of the outline
The outline stays visible at any zoom level

Canvas Size¶

Configure the target resolution via View > Canvas Size...

Preset resolutions:

Preset	Resolution	Use Case
RPi 7" Touchscreen	800 x 480	Raspberry Pi official touchscreen
SVGA	800 x 600	Standard small display
Wide 7"	1024 x 600	Wide-format 7" displays
XGA	1024 x 768	Standard monitor
HD 720p	1280 x 720	HD displays
WXGA	1280 x 800	Wide XGA
Full HD	1920 x 1080	Large displays
Custom	User-defined	Any size from 100 to 3840 px

The dialog includes a live proportions preview showing the aspect ratio with a dimensions label. When custom dimensions match a preset, the preset auto-selects.

When switching to runtime mode, the view auto-fits to the target resolution. The editor canvas remains unrestricted with margins beyond the target area.

Grid and Snap¶

View > Show Grid — toggle the alignment grid
View > Snap to Grid — snap elements to grid intersections during placement

Grid spacing and grid color are configurable via Preferences.

HMI Preferences¶

Open via File > Preferences (++ctrl+comma++).

Canvas settings:

Setting	Description
Background Color	Canvas background color
Grid Color	Grid line color (supports alpha for semi-transparent lines)
Grid Spacing	Grid cell size in pixels (5–100)

Buttons: OK, Cancel, Apply, and Restore Defaults.

Available Elements¶

Input Elements¶

Element	Description
Push Button	Momentary button — active while pressed
Toggle Switch	ON/OFF switch with two states
Selector Switch	Multi-position selector
Slider	Analog value control for N: region addresses
Numeric Entry	Direct numeric input for integer values

Output Elements¶

Element	Description
Indicator Lamp	Color-coded status indicator for bit addresses
Motor Indicator	Motor state display (running/stopped)
Numeric Display	Numeric value readout from N: region
Bar Graph	Visual bar chart for analog values
Trend	Time-series trend chart with history

Decoration Elements¶

Element	Description
Text Label	Static text label for annotation
Rectangle	Decorative shape for grouping
Background Image	Background image layer for panel layouts

Connecting to PLC Memory¶

HMI elements bind to PLC addresses via symbolic names. An HmiSymbolResolver translates symbols to addresses at runtime.

The HMI communicates through the IEngineContext interface:

forceBit() / writeBit() for digital inputs
writeInteger() for analog inputs
readBit() / readInteger() for indicators and displays