OBD2 Data Visualization Tool

A Windows application for visualizing and comparing CSV data. Built with PyQt6 and PyQtGraph for high-performance chart rendering. Built for the purpose of comparing OBDII data, but can be used for anything.

Features & User Guide

Data Import

• CSV File Loading: Open single or multiple CSV files via File menu or drag-and-drop
• Multi-Channel CSV Support: Handles interleaved multi-channel data (Car Scanner format) - automatically separates channels
• Past Imports: Home screen shows recently opened files for quick access
  • Double-click to reopen
  • Ctrl+Click for multi-select, then "Open Selected" to load multiple files at once
  • Clear History button to reset
• Add Import: Load additional CSV files to compare against the current data

Visualization

• Individual Channel Plots: Each channel displayed on its own graph with synchronized X-axis
• Multi-Import Overlay: Same channels from different files plotted on the same graph with different colors
• Click-to-Position Crosshair: Click anywhere on a chart to see exact values from all imports at that time
• Channel Title Values: Each chart title shows the current value at the crosshair position
• Adjustable Graph Heights: Taller/Shorter buttons adjust all chart heights by 5% increments
• LOD Optimization: Level-of-detail downsampling (max 2000 points) for smooth performance with large datasets
• Scroll Wheel: Scrolls the graph area vertically
• Ctrl+Scroll: Zooms X-axis in/out centered on last clicked position (or view center if none)

Time Navigation

Located in the sidebar:

• Start/End Time Inputs: Directly set the visible time range
• Center Time + Go: Jump to a specific time
• Navigation Buttons: ±0.1s, ±0.5s, ±1s, ±5s, ±15s, ±30s, ±1min, ±5min
• Zoom Slider: Drag left to zoom out (full range), right to zoom in (minimum 10 seconds)
  • Uses exponential scaling for natural zoom feel
  • Zooms centered on last clicked position (if within view), otherwise view center
• Reset View: Red button in center returns to full data range

Channel Visibility

In the sidebar below time navigation:

• Chart Checkbox: Single checkbox to show/hide the entire chart (determines Shown vs Hidden section)
• Import Dot Buttons: Colored circles next to each channel - click to toggle individual import lines
  • Solid circle = import line visible
  • Hollow ring = import line hidden
• Show All / Hide All: Quick toggle buttons for all channels
• Dynamic Sorting: Shown channels appear at top, sorted by unit then alphabetically

Import Management

In the "Imports" section of the sidebar:

• Color Legend: Each import has a distinct color (click the color dot to change it)
• Duration Display: Shows total time span of each import
• Time Offset: Shows offset relative to base import (first loaded)
• Sync Button: Opens synchronization dialog for non-base imports

Time Synchronization

When comparing multiple CSV files:

• Base Import: First loaded file is the reference (offset = 0)
• Synchronize Dialog: Click "Sync" button next to any additional import
  • Adjust time offset with ±0.1s to ±5min buttons
  • Or type offset directly
  • Charts update in real-time as you adjust

Math Channels

Create calculated channels from existing data:

• Create Math Channel Button: Opens the math channel dialog
• Up to 5 Inputs: Select channels A through E from dropdowns
• Expression Field: Python-style math expressions like (A/0.45) * 14.7 or A + B * C
• Real-time Validation: Expression must evaluate to a number
• Unit Selection: Autocomplete from existing units
• Edit Button: Modify existing math channels

Available Functions:

• Basic: abs, min, max, sqrt, log, log10, exp, pow
• Trig: sin, cos, tan
• Rounding: floor, ceil, round
• Statistical: rolling_avg(X, seconds), rolling_min, rolling_max, delta, cumsum
• Clipping: clip(X, min, max)
• Array-wide: np_min, np_max, np_mean, np_std
• Conditionals: if_else(condition, true_val, false_val)
• Constants: pi, e
• Comparisons: <, >, <=, >=, ==, !=

Data Filters

Show or hide data based on conditions:

• Create Filter Button: Opens filter dialog
• Filter Name: Required identifier
• Boolean Expression: Must evaluate to True/False (e.g., A > 100)
• Show/Hide Mode:
  • Show (👁): Display only matching data
  • Hide (🚫): Hide matching data
• Time Buffer: ±0.1s to ±10min around each match point
• Filter Precedence: Top filter = highest precedence (use up/down buttons to reorder)
• Cross-Import Sync: If any import matches, all imports show/hide that time range (respects offsets)
• Enable/Disable: Checkbox to toggle each filter without deleting

Window Layout

• Resizable Sidebar: Drag the splitter between sidebar and charts
• Split Window Mode: View menu → Detach sidebar to separate window (useful for dual monitors)
• Persistence: Window size, position, and splitter ratio saved between sessions

Saved Views

Save and restore complete analysis sessions:

• Save View: File → Save View (Ctrl+S) to save current state with a name
  • Pre-fills name if re-saving an existing view
• Home Screen: Saved views appear on the right side of the home screen
  • Double-click or select and click "Open Selected" to load
  • Delete button (🗑) next to each view for quick removal
  • "Delete All" button to clear all saved views
• Auto-prompt: When closing or opening new files, you'll be prompted to save (skipped if no changes)

What's saved in a view:

• CSV file paths (with relocation dialog if files move)
• Import colors and time offsets
• Math channels and filters
• Chart visibility (shown/hidden) and import line visibility per channel
• Time range and zoom level
• Graph heights (taller/shorter setting)
• Split window mode state

Storage location: Documents/OBD2Analyzer/views/

Data Format

The tool expects semicolon-delimited CSV files with these columns:

Column	Required	Description
SECONDS	Yes	Timestamp in seconds
VALUE	Yes	Sensor reading
UNITS	Yes	Unit of measurement (e.g., "rpm", "°F")
PID	Yes	Channel/sensor name

Example (Car Scanner format):

SECONDS;VALUE;UNITS;PID
0.0;800;rpm;Engine RPM
0.0;25;°C;Coolant Temp
0.1;850;rpm;Engine RPM
0.1;25;°C;Coolant Temp

The parser handles interleaved rows - different channels can have different sample rates.

Installation

Running the Executable

1. Ask Saurabh for obd2_analyzer.zip
2. Extract the zip
3. Run obd2_analyzer.exe

Developer Installation

1. Create and activate a virtual environment:

   python -m venv venv
   venv\Scripts\activate  # Windows
   # source venv/bin/activate  # Linux/Mac

2. Install dependencies:

   pip install -r requirements.txt

3. Run the application:

   python src/obd2_native.py

Building the Executable

Run the build script from the repo root:

run/build_exe.bat

This will:

1. Install PyInstaller if needed
2. Convert logo.png to run/logo.ico
3. Build the executable using run/obd2_analyzer.spec

Output will be in run/dist/obd2_analyzer.exe

Architecture

src/
├── obd2_native.py              # Application entry point
└── obd2_viewer/
    ├── core/                   # Core data processing
    │   ├── data_loader.py      # CSV file loading
    │   └── multi_channel_parser.py  # Multi-channel CSV parsing
    ├── dialogs/                # Dialog windows
    │   ├── loading_dialog.py   # Loading spinner
    │   ├── synchronize_dialog.py  # Time sync dialog
    │   ├── math_channel_dialog.py # Math channel creation
    │   ├── filter_dialog.py    # Filter creation
    │   └── expression_helpers.py  # Shared expression evaluation
    ├── widgets.py              # Reusable UI components
    ├── data_types.py           # Data structures (ImportData, etc.)
    ├── main_window.py          # Main application window
    └── chart_widget.py         # PyQtGraph chart components

Testing

# Run all tests
pytest src/test/ -v

Known Limitations

1. Data Format: Only supports semicolon-delimited CSV with SECONDS;PID;VALUE;UNITS columns
2. Export: No chart export functionality yet
3. Sessions: No way to save/restore visualization sessions

Roadmap

• Chart export (PNG, SVG)
• Data annotations and markers
• Session save/restore
• Additional CSV format support

Past Issues & RCAs

PyInstaller PyQt6 DLL Load Failure (Dec 2025)

Issue: DLL load failed while importing QtWidgets when running the PyInstaller-built exe

Root Cause: PyQt6 6.10.1 has DLL loading compatibility issues with PyInstaller on Windows. Additionally, shiboken2 (PySide2's Qt5 binding) was being bundled and conflicting with PyQt6.

Solution:

1. Downgraded PyQt6 to 6.5.2
2. Added exclusions for PySide2, shiboken2, PySide6, shiboken6, PyQt5 in spec file
3. Pinned PyQt6 version in requirements.txt to >=6.5.0,<6.6.0

Saved View Loading Async Issue (Dec 2025)

Issue: "No files could be loaded from this view" error and app hanging when loading a saved view

Root Cause: _load_file() uses a background thread and returns immediately. The view manager was checking mw.imports and trying to apply colors/offsets before files finished loading, resulting in empty imports list.

Solution:

1. Refactored load_saved_view to queue files using main window's existing queue system
2. Added _on_view_files_loaded callback that runs after all files finish loading
3. Updated _load_next_queued_file to call the callback when queue empties
4. Added null checks for _loading_dialog since saved view loading doesn't create one

Frontend Callback Failure (Dec 2024)

Issue: Dash callbacks not triggering graph display (legacy web version)

Root Cause: Dashboard was creating its own Dash app instance, but callbacks were registered on a different instance.

Solution: Modified dashboard to accept external Dash app for callback registration.

License

This project is licensed under the MIT License - see the LICENSE file for details.

Acknowledgments

• Built with PyQt6
• Charts powered by PyQtGraph
• Data processing with Pandas and NumPy
• Data format from Car Scanner