# Decode real car and gauge signals with a custom CAN sniffer

Reads real CAN-bus traffic, aligns it with dashboard video or human-moved gauges, and produces usable signal definitions and live visualizations. Demonstrated vehicle speed decoding and physical gauge-position decoding.

## Hardware
CSS Electronics CANsub.2; OBD2-DB9 cable; Opel Astra in live vehicle example; optional CANmod.input and potentiometer board

A physical CAN interface captures signals from a vehicle or test gauges for decoding.

## Shopping list

Use listen-only capture and correct cable pinout; do not transmit vehicle control commands or operate the computer while driving.

Quantities are for one build. Unless marked source-specified, they are planning quantities; confirm kit contents and the chosen configuration before ordering.

### Confirm before buying
- Optional reference-board model and vehicle-specific bus access require confirmation.

### 1 × CSS Electronics CANsub.2
- Requirement: Required
- Quantity basis: Planning quantity for one build; check the selected configuration
- Purpose: Capture CAN traffic.
- Destination: https://www.csselectronics.com/products/can-fd-usb-interface-ethernet-cansub-2
- Match: Product page
- Link review: Page checked; stock not assessed
- Evidence: Creator source
- Source: https://www.csselectronics.com/pages/can-bus-reverse-engineering-ai-llm-claude
- Source: https://github.com/CSS-Electronics/can-bus-reverse-engineering-skills

### 1 × OBD2-to-DB9 adapter cable
- Requirement: Required
- Quantity basis: Planning quantity for one build; check the selected configuration
- Purpose: Connect vehicle diagnostic socket to interface.
- Destination: https://www.csselectronics.com/products/obd2-db9-adapter-cable
- Match: Exact creator-recommended accessory
- Link review: Page checked; stock not assessed
- Evidence: Creator source
- Source: https://www.csselectronics.com/pages/can-bus-reverse-engineering-ai-llm-claude
- Source: https://github.com/CSS-Electronics/can-bus-reverse-engineering-skills

### 1 × USB (CANsub-compatible) data cable
- Requirement: Required
- Quantity basis: Planning quantity for one build; check the selected configuration
- Purpose: Connect to the computer for programming or data.
- Notes: Connect the CANsub to the analysis computer.
- Sourcing: Use existing equipment or match the specification above. No exact purchase link verified.
- Evidence: Setup requirement — check against your configuration
- Source: https://www.csselectronics.com/pages/can-bus-reverse-engineering-ai-llm-claude
- Source: https://github.com/CSS-Electronics/can-bus-reverse-engineering-skills

### 1 × Computer for capture and decoding
- Requirement: Required
- Quantity basis: Planning quantity for one build; check the selected configuration
- Purpose: Build, configure or flash the software.
- Notes: Run webCAN / Python capture tools.
- Sourcing: Use existing equipment or match the specification above. No exact purchase link verified.
- Evidence: Setup requirement — check against your configuration
- Source: https://www.csselectronics.com/pages/can-bus-reverse-engineering-ai-llm-claude
- Source: https://github.com/CSS-Electronics/can-bus-reverse-engineering-skills

### 1 × Vehicle / live CAN source
- Requirement: Required
- Quantity basis: Planning quantity for one build; check the selected configuration
- Purpose: Provide traffic to decode.
- Notes: Creator’s live example used an Opel Astra; access to proprietary CAN data differs by vehicle.
- Sourcing: No exact purchase link verified; confirm the model and requirements above before ordering.
- Evidence: Creator source
- Source: https://www.csselectronics.com/pages/can-bus-reverse-engineering-ai-llm-claude
- Source: https://github.com/CSS-Electronics/can-bus-reverse-engineering-skills

### 1 × Contactless CAN reader
- Requirement: Optional
- Quantity basis: Planning quantity for one build; check the selected configuration
- Purpose: Alternative capture connection.
- Notes: May help when desired traffic is not exposed at the OBD port; follow the manufacturer wiring guide.
- Destination: https://www.csselectronics.com/products/contactless-can-bus-reader-adapter
- Match: Creator-recommended optional accessory
- Link review: Page checked; stock not assessed
- Evidence: Creator source
- Source: https://www.csselectronics.com/pages/can-bus-reverse-engineering-ai-llm-claude
- Source: https://github.com/CSS-Electronics/can-bus-reverse-engineering-skills

### 1 each × CANmod.input and potentiometer board
- Requirement: Optional
- Quantity basis: Planning quantity for one build; check the selected configuration
- Purpose: Controlled reference signal experiment.
- Notes: Not required for a basic vehicle capture; exact potentiometer board not identified.
- Sourcing: No exact purchase link verified; confirm the model and requirements above before ordering.
- Evidence: Creator source
- Source: https://www.csselectronics.com/pages/can-bus-reverse-engineering-ai-llm-claude
- Source: https://github.com/CSS-Electronics/can-bus-reverse-engineering-skills

Source reviewed, not assembled or hands-on tested. A working product page does not confirm stock, firmware compatibility or a complete build.

## Setup
Specialist tools

## Coding tool
Claude Code

## How the agent helped
Martin Falch's 'How I built the skill (or asked Claude to)' section says he deliberately did not create the Python tools himself, instead directing Claude through test cases and corrections; the article shows the resulting software operating with CANsub hardware.

## Before you build
Use listen-only capture. Wiring and reference signals require expertise; decoded results are not safety-certified. Do not transmit control commands to a vehicle.

## Sources
- Original build: https://www.csselectronics.com/pages/can-bus-reverse-engineering-ai-llm-claude
- Supporting source: https://github.com/CSS-Electronics/can-bus-reverse-engineering-skills

Source reviewed 2026-11-04. Not hands-on tested.