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+# OBD2 Terminal Dashboard
+
+This repository contains a Textual-based terminal dashboard for querying an OBD-II adapter and presenting live vehicle telemetry alongside raw command output.
+
+`scanbus.py` is intentionally excluded from this README.
+
+## What It Does
+
+- Displays live dashboard metrics for speed, RPM, fuel level, oil temperature, and coolant temperature.
+- Renders a command table for OBD modes `01`, `02`, `03`, `04`, `06`, `07`, and `09`.
+- Polls commands asynchronously with a global queries-per-second limit.
+- Deduplicates concurrent reads of the same OBD command.
+- Caches command results using a default TTL plus per-command overrides from `command_ttl.conf`.
+- Supports a simulated mode for UI development without a physical adapter.
+- Streams application logs inside the terminal UI.
+
+## Repository Layout
+
+- `obd2_tui.py`: main Textual app, CLI entry point, keyboard bindings, command polling, and inline TTL editing.
+- `obd2_interface.py`: async OBD abstraction, connection lifecycle, rate limiting, caching, TTL config reloads, and simulation support.
+- `models.py`: Pydantic models for the live telemetry report and scan definitions.
+- `ui.css`: Textual stylesheet for the dashboard, command table, and log panel.
+- `command_ttl.conf`: command-specific cache TTL overrides in milliseconds.
+- `test.py`: unit tests for report normalization, interface behavior, caching, TTL updates, simulation, and UI helpers.
+- `requirements.txt`: Python dependencies.
+
+## Architecture
+
+The application has two main layers:
+
+1. `OBD2App` in `obd2_tui.py`
+   - Builds the terminal UI with Textual.
+   - Polls a small set of key telemetry commands continuously for the metric cards.
+   - Polls the currently visible rows in the selected OBD mode table.
+   - Lets the user edit a selected command's cache TTL from the UI.
+
+2. `OBD2Interface` in `obd2_interface.py`
+   - Connects to the adapter through `python-OBD`.
+   - Serializes outbound queries through a worker queue.
+   - Enforces a global rate limit.
+   - Maintains a TTL cache keyed by command name.
+   - Watches `command_ttl.conf` and hot-reloads TTL overrides.
+
+`SimulatedOBD2Interface` swaps in a fake connection that generates dynamic values for development and testing.
+
+## Requirements
+
+- Python 3.11+ recommended
+- An ELM327-compatible OBD-II adapter for real vehicle data
+- Terminal support suitable for a Textual application
+
+Install dependencies:
+
+```bash
+python3 -m venv .venv
+source .venv/bin/activate
+pip install -r requirements.txt
+```
+
+## Running
+
+Run against a real OBD adapter:
+
+```bash
+python3 obd2_tui.py
+```
+
+Run in simulated mode:
+
+```bash
+python3 obd2_tui.py --simulated
+```
+
+Optional flags:
+
+- `--qps`: maximum OBD queries per second across the app. Default: `10.0`
+- `--ttl-config`: path to the TTL override file. Default: `command_ttl.conf`
+
+Example:
+
+```bash
+python3 obd2_tui.py --simulated --qps 25 --ttl-config command_ttl.conf
+```
+
+## UI Behavior
+
+The dashboard is composed of:
+
+- Metric cards for the five primary telemetry values
+- A command table for the selected OBD mode
+- A TTL editor bound to the currently highlighted command
+- An in-app log panel
+
+The polling strategy is selective:
+
+- Core telemetry commands are always queried so the metric cards stay current.
+- The mode table queries only commands that are currently visible in the viewport.
+- Duplicate requests for the same command are coalesced through the interface queue and cache.
+
+## Keyboard Controls
+
+- `q`: quit
+- `b`: toggle metric card border style
+- `e`: focus the TTL editor
+- `escape`: return focus to the command table
+- `left` / `right`: previous or next OBD mode
+- `shift+up` / `shift+down`: jump to top or bottom of the table
+- `1`, `2`, `3`, `4`, `6`, `7`, `9`: switch directly to that OBD mode
+
+## TTL Configuration
+
+`command_ttl.conf` uses the format:
+
+```text
+COMMAND_NAME,ttl_ms
+```
+
+Examples:
+
+```text
+SPEED,10
+RPM,10
+FUEL_LEVEL,5000
+GET_DTC,86400000
+```
+
+Notes:
+
+- TTL values are stored in milliseconds.
+- A value of `0` effectively disables caching for that command.
+- The app reloads the file automatically while running.
+- Editing a TTL in the UI writes the updated value back to the configured TTL file.
+
+## Testing
+
+Run the unit tests with:
+
+```bash
+python3 -m unittest -v test.py
+```
+
+The tests cover:
+
+- Report value normalization
+- Query rate limiting
+- Cache hit and cache expiry behavior
+- TTL override parsing and persistence
+- Simulated connection behavior
+- Display formatting and duration parsing helpers
+
+## Current Environment Note
+
+In the current workspace environment, `python3 -m unittest -v test.py` fails immediately because `pydantic` is not installed. After installing dependencies from `requirements.txt`, the test command should be rerun.
+
+## Development Notes
+
+- Logging is routed into the Textual `RichLog` panel through a custom logging handler.
+- The codebase uses `Report` as the shared mutable telemetry state for the UI.
+- `command_ttl.conf` is large because it predefines cache behavior for many standard OBD commands.
+- `obd2_interface.py` also contains a non-TUI `__main__` path that continuously logs report snapshots, but the primary entry point for normal use is `obd2_tui.py`.