Introduction

CanLover is a desktop application for analysing, decoding, and interacting with CAN bus networks. It supports live connections to physical hardware adapters as well as offline replay of recorded log files, and it provides a set of specialised windows for inspecting raw traffic, decoded signals, diagnostic trouble codes, network topology, and bus health.

Main Features

• Multi-channel live capture from PEAK, Vector, and Kvaser hardware adapters
• Signal decoding via DBC and SYM database files
• J1939 support — PGN/SPN decoding, address claims, DM1/DM2 DTCs, and DM25 freeze frames
• Replay of ASC, TRC, and BLF log files with timeline scrubbing and variable speed
• Signal plotting with configurable multi-panel layouts and drag-and-drop assignment
• Node Logic — visual scripting engine: wire event, logic, data, and action nodes to automate CAN behaviour without writing code
• CAN transmit with periodic scheduling and animated signal waveforms (ramp, sine)
• Bus statistics — real-time load, error counters, and traffic breakdown per channel
• Database browser — visual bit-layout inspector for DBC and SYM files
• Session recording exportable to ASC, TRC, or BLF

Supported Platforms

Application Layout

CanLover uses a dockable window layout. All windows can be freely repositioned, resized, tabbed, and undocked. The layout is preserved between sessions.

A session starts with the Bus Configuration window, where you select hardware channels, attach database files, and connect. Once connected (or a replay is loaded), the remaining windows populate with live data.

Licensing

Some features require a valid license file. CanLover will load a license from the application data directory automatically on startup. See the Licensing section for details on which features require a license.

Diagnostic Report

If you encounter a problem and need to contact support, use Help → Send Diagnostic Report… to send a report directly to the developer. The report includes your application version, operating system, CPU model, hardware fingerprint, license status, and the last 100 lines of the application log. A preview of the report is shown before sending so you can review its contents. The report is transmitted over HTTPS and requires an active internet connection.

Bus Configuration

The Bus Configuration window is the starting point for every session. Open it with the Configure… button in the main toolbar. It covers device discovery, channel setup, database attachment, and session management.

Discovering Devices

Click Refresh Devices to enumerate all connected CAN adapters. Detected hardware is displayed in a collapsible list grouped by device, showing the device type, serial number, and the number of available channels.

If a device does not appear, verify that the vendor driver is installed and the adapter is powered on before clicking Refresh.

Configuring Channels

Expand a device entry to reveal its individual channels. For each channel:

Only channels with the enable checkbox ticked will be opened when you connect.

Attaching Database Files

Each channel can have one or more database files attached for signal decoding:

• +DBC — attach a DBC file (CAN database with message and signal definitions)
• +SYM — attach a SYM file (Peak Symbol Editor format)

A file browser opens to select the file. Multiple files can be attached to the same channel; signals from all files will be decoded concurrently.

J1939 Options

When a DBC or SYM file containing J1939 messages is loaded, an additional J1939 section appears with options for BAM assembly, SPN decoding, and CSV-based SPN description lookup.

Connecting

Once channels are configured and databases are attached, click Connect Active Channels. CanLover opens all enabled channels at the selected bitrates and begins capturing traffic.

A recording starts automatically when you connect. The status bar shows elapsed recording time.

Replay Sessions

To replay a previously recorded file instead of connecting to hardware:

1. Click + Add Replay File and select an ASC, TRC, or BLF file.
2. Attach decoder files (+DBC/+SYM) to any replay channel as needed.
3. Use the playback controls at the bottom of the window:

Multiple files can be added and will be played in sequence as a single concatenated recording.

Stopping a Replay

Clicking Stop Replay ends the replay session and restores the channel configuration to the state it was in before the replay started, allowing you to reconfigure channels, change bitrates, or connect to hardware immediately.

If the replay produced a recording that has not been saved yet, CanLover will ask whether to save it before stopping. Choose Save to export the recording, Discard to drop it, or Cancel to return to the replay without stopping.

Saving a Recording

Before disconnecting or connecting to a different device, CanLover offers to save the current session recording. The save dialog supports three formats:

Choose a format, set the output path, and click Save. Selecting Discard discards the in-memory recording without saving.

Raw Trace

The Raw Trace window shows every CAN frame that passes through the session, in real time. It has two complementary view modes selectable via tabs at the top.

When a session is opened, the active view mode is chosen automatically: if at least one channel has a DBC or SYM file attached, the window opens in Unique mode so decoded signal data is immediately visible; otherwise it opens in Trace mode. You can switch modes freely at any time during the session.

Trace Mode

Trace mode is a chronological log of all frames in the order they were received or transmitted, up to an internal buffer of approximately 16 000 entries.

Columns

TX frames are highlighted with a subtle blue background to distinguish them from received traffic.

Sorting

Click any column header to sort the visible rows by that column. Clicking the same header again reverses the order; a third click removes the sort and restores insertion order. The Data column cannot be sorted.

Controls

Hovering over a frame row shows a tooltip with the decoded signal values for that frame, if a database is loaded.

Unique Mode

Unique mode consolidates the stream into one row per CAN ID, showing only the most recent data for each message. This gives an at-a-glance view of all active messages on the bus.

Columns

Rows whose data changed within the last 500 ms are highlighted in amber, making it easy to spot active messages.

Sorting

Click any column header to sort by that column (ascending → descending → none). The Data / Value and Unit columns cannot be sorted.

Signal Expansion

If a database is loaded, each row in Unique mode can be expanded (click the arrow) to reveal the decoded signals for that message. Multiplexed messages show a sub-level for each active multiplexer value.

Signal Table

The Signal Table window provides a real-time tabular view of every decoded signal value across all loaded databases. It requires at least one DBC or SYM file to be attached to an active channel.

License required: DBC/SYM signal decoding requires the DBC Decoder feature in the license.

Layout

Each row represents a single signal. Signals are grouped by their parent message name.

The total number of decoded signals is shown in the top-right corner of the window.

Controls

Highlights

Rows whose value changed within the last 500 ms are highlighted in green. This makes it easy to see which signals are currently active and changing, especially on a busy bus.

Usage Tips

• Use the filter box with a message name to focus on the signals of a specific ECU.
• Combine with the Signal Plot window to quickly identify which signals are worth plotting: find the signal of interest here, then drag it from the plot window’s signal browser onto a canvas cell.
• In replay mode, the table reflects the signal values at the current playback position. Scrubbing the timeline updates all rows accordingly.

Signal Plot

The Signal Plot window visualises signal values as time-series charts. Signals can be freely assigned to a configurable grid of plot panels.

License required: Signal plotting requires the Signal Plot feature in the license.

Signal Browser

The left sidebar contains a hierarchical browser listing all decoded signals, organised by message name. Use the filter box at the top of the sidebar to search by message or signal name.

Adding Signals to a Plot

Drag a signal from the sidebar and drop it onto any panel in the plot canvas. Each panel accepts multiple signals and assigns a distinct colour automatically (up to eight colours before cycling).

To remove a signal, right-click anywhere on the panel and select Remove signal from the context menu.

Layout

The toolbar above the canvas contains a layout picker that sets the grid arrangement of panels:

Changing the layout preserves existing signal assignments where possible.

Stacked vs. Shared Axis Mode

Each panel supports two display modes, toggled from the right-click context menu:

• Shared axis — all signals in the panel share a single Y axis and are overlaid on one chart. Useful when signals have similar ranges.
• Stacked — each signal gets its own sub-plot with an independent Y axis. The X axes are linked so panning one pans all. Useful for comparing signals with very different scales.

Zoom and Navigation

The plot canvas is interactive:

• Scroll to zoom the X axis (time axis)
• Middle-click drag to pan
• Double-click to reset zoom to the full history window

In live mode the X axis spans a rolling history window. In replay mode it spans the full recording length, and a cursor marker shows the current playback position on every signal.

Markers

The toolbar contains a marker threshold setting (default 50). When the number of visible samples falls below this threshold (i.e., you are sufficiently zoomed in), individual sample markers appear on the plot lines to show the exact measurement points.

Controls

DTC Panel

The DTC Panel displays active Diagnostic Trouble Codes (DTCs) reported by J1939 nodes on the network. It processes DM1 (active faults) and DM2 (previously active faults) messages as they arrive.

License required: The DTC Panel requires the DTC Panel feature in the license. Protocol requirement: A J1939 database must be loaded for SPN and FMI descriptions to appear.

Layout

The header shows the total count of active DTCs. The Clear button removes all entries from the list.

Each row in the table represents one DTC:

Deduplication

If the same SPN + FMI combination from the same source address is received more than once, the existing row is updated rather than creating a duplicate. The occurrence count reflects the latest value from the node.

Usage Tips

• The Source column shows the raw J1939 address in hex. Cross-reference with the J1939 Network window to identify the reporting node by manufacturer and function code.
• Sort by Time to see the chronological order in which faults appeared.
• Sort by Source to group all faults from the same ECU together.

Freeze Frame

The Freeze Frame window captures and displays J1939 DM25 (Expanded Freeze Frame) data — a snapshot of signal values recorded by an ECU at the moment a fault was triggered.

License required: Freeze Frame requires the Freeze Frame feature in the license. Protocol requirement: Requires J1939 and a loaded database with DM25 support.

Layout

The window is split into two panels.

Left Panel — Snapshot List

Lists all freeze frame snapshots received during the session. Each entry shows:

• Timestamp — session time when the snapshot was received
• Source — J1939 source address of the reporting node (hex)
• Trigger SPN — the Suspect Parameter Number that caused the fault

Click a snapshot to select it and view its contents in the right panel.

Right Panel — Snapshot Detail

Displays the contents of the selected snapshot:

Below the header, a table lists all captured signals with their physical values at the time of the fault. These values are immutable — they represent the state of the system at the moment the fault was detected, not the current live values.

Controls

Usage Tips

• Use freeze frames in conjunction with the DTC Panel to correlate a fault code with the operating conditions present when the fault occurred.
• Multiple snapshots from different ECUs or different fault events accumulate over the session, allowing comparison between events.

J1939 Network

The J1939 Network window shows the nodes discovered on the J1939 network by listening for Address Claim (PGN 0xEE00) messages. It provides a quick topology overview of which ECUs are present on the bus.

Protocol requirement: Requires a J1939-enabled channel. Nodes only appear after they have transmitted an Address Claim message.

Layout

The header shows the total count of discovered nodes.

Each row in the table represents one network node:

Behaviour

• Nodes are added the first time an Address Claim is received from a new source address.
• If the same source address transmits a new Address Claim (e.g., after an address conflict resolution), the existing row is updated with the new NAME information.
• Nodes accumulate over the session; there is no automatic expiry.

Usage Tips

• Use this window to confirm all expected ECUs are present and have successfully claimed their addresses before starting a diagnostic session.
• Cross-reference the Source column in the DTC Panel with the addresses shown here to identify which physical node is reporting a fault.
• The J1939 standard assigns well-known function codes (e.g., 0x00 = Engine, 0x04 = Transmission). Consult the J1939-81 specification or your system documentation for the full list.

Database Browser

The Database Browser lets you inspect the contents of loaded DBC and SYM database files — message definitions, signal properties, and visual bit layouts — without needing an active CAN session.

License required: The Database Browser requires the Database Browser feature in the license.

Opening a Database

If a database is already attached to an active channel via the Bus Configuration window, it is automatically shown in the browser. To browse a file independently of any session, click the Load button and select a DBC or SYM file.

If a session database is configured after an ad-hoc file is loaded, the session database takes priority and the ad-hoc file is dismissed.

Left Panel — Channel and Message List

The left panel shows a tree of channels, each with the count of messages defined in its database. Expand a channel to see its messages listed by CAN ID and name. Click a message to select it and view its details in the right panel.

The divider between the left and right panels can be dragged left or right to resize them. This is useful when message names are long and would otherwise be truncated.

Right Panel — Message Detail

The right panel has four tabs for the selected message.

Signals Tab

A table of all signals defined in the message:

Hovering over a row shows a tooltip with any value descriptions (named enumeration values) defined for that signal in the database.

Bit Layout Tab

A colour-coded grid showing the physical bit positions occupied by each signal within the 8-byte CAN data field.

• Rows represent bytes (byte 0 at the top).
• Columns represent bits within each byte (bit 7 on the left, bit 0 on the right).
• Each signal is rendered in a distinct colour. A colour legend below the grid identifies which signal corresponds to which colour.

For multiplexed messages, a combo box above the grid selects the multiplexer value. The layout updates to show the signals valid for the selected mux value.

Value Tables Tab

Shows the enumeration tables for signals that have named values defined in the database. Each such signal is listed by name; beneath it a two-column table maps each raw integer value to its human-readable description. Signals with no value table are omitted. If no signal in the message has a value table, the tab shows a note to that effect.

Validation Tab

Analyses the message definition and reports potential problems. Issues are shown in a table with a severity indicator and a description.

Overlapping bits between multiplexed signals that belong to different multiplexer values are not flagged, because those signals are never active at the same time. If no issues are found, the tab displays a confirmation that the message definition is valid.

CAN Transmit

The CAN Transmit window allows you to compose, schedule, and send CAN frames. It supports both raw frames with manually edited bytes and database-backed frames with per-signal value control and animated waveforms.

Adding Frames

Use the toolbar buttons to add entries:

• + Add from DBC — opens a dialog to select a message from any loaded DBC or SYM database. The entry is pre-populated with all signals and their default values.
• + Add Raw — opens a dialog to define a raw frame by CAN ID, DLC, and initial data bytes.

Entries can be removed by right-clicking the entry header and selecting Remove.

Sending Frames

Each entry has two send modes:

The period field sets the interval in milliseconds between successive transmissions. When periodic transmission is active, the entry header displays the current period.

DBC Message Entries

For frames added from a database, the entry expands to show a signal table:

Signal Behaviors

The Behavior column controls how the signal value changes on each periodic transmission:

The Period mult. setting controls how many frame transmissions make up one full waveform cycle. The minimum effective cycle is 200 ms.

Animated signals (any mode other than Fixed) show the current animated value in the value column as read-only. Switch back to Fixed to regain manual control.

Enum Signals

Signals with named value descriptions in the database show a dropdown instead of a numeric input or slider. Select a value by name from the dropdown.

Raw Frame Entries

Raw entries show a DLC selector and a row of byte fields. Each byte is edited as a two-digit hexadecimal value (00–FF). The raw bytes are sent as-is without any database encoding.

CAN Statistics

The CAN Statistics window shows real-time bus health metrics for every active channel — bus load, traffic counters, error rates, and hardware status.

Layout

The window contains one collapsible section per active channel. The section header shows the channel index, device identifier, channel type (Physical, Virtual, or Replay), and configured bitrate.

A Reset button in the top-right corner of each physical channel header resets the hardware error counters on the adapter.

Replay channels display a “Statistics not available” message — metrics are not meaningful for file-based sessions.

Bus Status

Shows the current hardware error state reported by the adapter:

TEC (Transmit Error Count) and REC (Receive Error Count) are shown below the state when the hardware supports reading them. Values are colour-coded: green below 96, yellow up to 127, orange up to 255, red at bus-off threshold.

Bus Load

A colour-coded progress bar provides an at-a-glance view: green below 50 %, yellow at 50 %, red above 50 %. Hardware load readings from the adapter are shown separately when available.

Traffic

Counts of frames observed since the session started, broken down by frame type:

Received: Total, Extended ID, CAN FD, Remote
Transmitted: Total, Extended ID, CAN FD
Bytes: Total bytes received and transmitted

Error Frames

A breakdown of CAN error frames by error type:

Error counts are colour-coded on a logarithmic scale: dimmed when zero, yellow for 1–9, orange for 10–999, red for 1 000 and above.

Licensing

CanLover uses a feature-based licensing system. A subset of windows and capabilities requires a valid license file; the rest of the application runs without one.

License File

The license is a JSON file placed in the CanLover application data directory. It is loaded automatically at startup. No manual import step is required — simply copy the license file to the correct location and restart the application.

The expected location on each platform:

License Properties

A license with an expiry date will stop granting access to licensed features after the expiry date. The application continues to run with unlicensed features available.

Licensed Features

Features not listed above (Raw Trace, CAN Statistics, CAN Transmit with raw frames, Bus Configuration) are available in all configurations without a license.

Obtaining a License

Contact the CanLover sales team to purchase a license. Provide your machine identifier, which can be found in the About dialog under Help → About. License files are issued per machine and cannot be transferred to a different computer.

License Validation

CanLover verifies the license signature using an embedded Ed25519 public key on every startup. Tampered or incorrectly generated license files are rejected. The application also monitors system time integrity to prevent circumventing expiry dates by setting the clock back.

Workspaces

Workspaces let you save and restore the visual layout of the application — which windows are open, where they are docked, and how the dockspace is arranged. Each workspace is independent; switching between them instantly loads the saved layout without affecting the active bus session or any channel configuration.

The Workspace Tab Bar

A tab bar sits just below the toolbar. Each tab represents one saved workspace. Click a tab to switch to that layout.

When you add a new workspace you can choose:

• New empty — starts with all windows floating at their default positions.
• Duplicate current — copies the current layout as a starting point.

Saving and Loading

Workspaces are saved automatically to workspaces.json in the application configuration directory when the application exits, and loaded again on the next startup. The last active workspace is restored.

You can also save and load workspaces to arbitrary files via the File menu:

Exported workspace files are plain JSON and can be shared between machines or committed to version control alongside a project.

What Is Saved

Each workspace stores:

• Docking layout — the full ImGui dockspace state (window positions, sizes, split ratios, tab groupings).
• Window visibility — which windows are open or hidden.

The following are not part of a workspace and are shared across all workspaces:

• Hardware channel configuration (adapters, baud rates, database assignments).
• Active bus connection or replay state.
• Application settings such as the colour theme.

Configuration Directory

Workspaces are persisted in the platform-specific configuration directory alongside canlover_settings.json:

Node Logic

Node Logic is a visual programming environment built into CanLover. Wire together event, logic, data, and action nodes on a canvas to create scripts that react to live CAN traffic — no code required.

License required: Node Logic requires the Node Logic feature in the license.

Opening the Editor

Open the Node Logic window from Windows → Node Logic in the main menu bar. The window contains a toolbar at the top, a log panel, and the node canvas below.

Toolbar

The current graph name is shown in the toolbar next to the separator when a named graph is loaded. While the graph is running, node and link editing is locked — the canvas is read-only until you press Stop.

Concepts

Event Nodes

Execution always starts at an event node. When the node’s condition fires, the graph traverses the exec chain connected to that node’s exec output.

Exec (Flow) Nodes

Exec nodes control the flow of execution.

Data Nodes

Data nodes compute values. They are evaluated lazily when an exec node reads their output, and the result is memoised for the duration of a single event firing.

Action Nodes

Action nodes interact with the CAN session. They require an open CAN library to be loaded; the validator blocks the graph from starting if action nodes are present but no hardware (or virtual) session is active.

Building a Graph

1. Right-click on the canvas to open the node browser. Type to filter by name, then click a node type to place it.
2. Drag from any output pin to a compatible input pin to create a link. Incompatible pin types show a red indicator.
3. Double-click a node header (or click the … button) to open its configuration popover (CAN ID, timer interval, signal name, comparison operator, etc.).
4. Press Run in the toolbar. Any validation errors appear in the log and must be resolved before execution begins.
5. Press Stop to halt at any time.

Pin Types and Connections

Numeric types (Bool, Int, Float) accept each other with automatic coercion: a Float connected to an Int pin truncates to integer; a Bool connected to a Float pin yields 0.0 or 1.0.

Validation

The validator runs automatically when you press Run. Common errors:

Warnings (non-blocking) are shown for disconnected event nodes and unreachable subgraphs.

Execution Model

• Thread safety: the entire graph runs on the render thread. CAN receive, decode, and TX threads are never touched — a slow graph only lowers frame rate, never drops CAN frames.
• OnTimer fires at most once per rendered frame. At 60 FPS the minimum effective interval is ≈ 16 ms.
• CAN-driven events (OnMessageReceived, OnDBCMessageReceived, OnSignalChanged) fire synchronously inside drain() and therefore see fully decoded signal values for the current frame batch.
• SendDBCMessagePeriodic is driven by tick() on each rendered frame; it fires independently of any event chain.
• Data node memoisation: each data node evaluates at most once per event firing. Subsequent reads within the same chain return the cached result.

Saving and Loading

Graphs are stored as JSON files in a graphs/ folder inside the application configuration directory. The Save As… button saves under a user-chosen name; Load lists all named graphs in a dropdown.

The most recently used graph is saved automatically to node_graph.json (the autosave slot) whenever the Node Logic window is closed or a different graph is loaded. It is restored automatically when the window is next opened. To include the graph in a workspace, use File → Save Workspace.

Usage Tips

• Use a Sequence node to fan out from a single event to multiple action chains.
• DoOnce before a SendFrame is a clean way to send an initialisation frame exactly once when the session starts — connect OnSessionStart → DoOnce → SendFrame.
• Use SetVariable / GetVariable to pass data between independent event chains without running wires across the canvas.
• Keep OnTimer intervals above 50 ms for periodic CAN TX — very short intervals can saturate the bus.
• The Counter node combined with Branch lets you trigger an action every N-th frame rather than every frame.
• OnDBCMessageReceived lets you react to specific decoded messages without knowing the raw CAN ID — configure the message name and select which signal values to expose as Float outputs.
• SequenceValue in wrap mode is useful for cycling through a test pattern (e.g., RPM sweep) automatically each time a timer fires; in bounce mode it reverses direction, producing a triangle-wave sequence without extra logic.
• SendDBCMessagePeriodic is the easiest way to keep a DBC message on the bus at a fixed rate — drop it on the canvas, configure message name and interval, wire up signal value sources, and press Run. No event node or exec chain needed.