LIN-CAN Gateway for Heated/Ventilated Seat Buttons

Overview

This project implements a bidirectional protocol gateway between LIN and CAN buses to integrate repurposed OEM heated/ventilated seat button modules into a 2020 Ram 1500. The gateway translates button presses from the LIN bus into CAN messages for the vehicle's Body Control Module (BCM), and translates heat/vent intensity and backlighting commands from the CAN bus into LIN commands for the button module LEDs and backlighting.

Final Product: src/gateway/gateway.ino | Documentation

Demo Videos

• Button Functionality - Controlling heat and vent settings
• Backlighting Integration - Buttons working in concert with center stack

Project Structure

├── src/                          # Source code
│   ├── gateway/                  # Final LIN-CAN gateway (production)
│   ├── BusSniffer/               # Bus capture tool for reverse engineering
│   └── test/                     # Test sketches for protocol validation
├── docs/                         # Documentation and analysis
│   ├── CAN_analysis/             # Python scripts for CAN protocol analysis
│   ├── LIN_analysis/             # Python scripts for LIN protocol analysis
│   └── references/               # Datasheets and connector terminations
├── HARDWARE.md                   # Hardware specifications and components
├── WIRING.md                     # Wiring diagrams and connections
├── MOUNTING.md                   # Enclosure and mounting information
├── METHODOLOGY.md                # Software development methodology and approach
└── README.md                     # This file

Hardware

Mounting

Wiring

Software Development

Required Libraries

Install these libraries via Arduino Library Manager:

• LIN_master_portable_Arduino by Georg Icking
• ESP32-TWAI-CAN by sorek (handmade0octopus)

Features

Gateway Functionality

• LIN to CAN: Translates button presses to CAN events (ID 0x302)
• CAN to LIN (LEDs): Translates heat/vent intensity commands (ID 0x31E) to button LED states
• CAN to LIN (Backlight): Translates brightness commands (ID 0x2FA) to button backlighting
• Button Debounce: 300ms debounce prevents multiple triggers
• Diagnostic LED: RGB LED provides visual feedback for system state

Protocol Details

• LIN Bus: 19,200 baud, LIN 2.0, 50Hz polling rate
• CAN Bus: 125 kbps, normal mode (TX + RX)
• Power Consumption: ~0.36W (0.03A @ 12V)
• Security: WiFi and Bluetooth disabled

Getting Started

1. Hardware Setup

1. Connect the ESP32 board to the vehicle's CAN bus and 12V DC power via the center stack display screen connector C1
2. Connect the LIN bus to the seat button modules (dedicated LIN bus with only ESP32 and button modules)

2. Arduino IDE Configuration

Select the following board settings:

• Board: ESP32S3 Dev Module
• USB CDC On Boot: Enabled
• PSRAM: OPI PSRAM
• Upload Mode: USB-OTG CDC (TinyUSB)

3. Upload Gateway Firmware

1. Open src/gateway/gateway.ino
2. Upload to the board
3. Open Serial Monitor at 115,200 baud to view diagnostic messages

Pin Configuration

Function	Pin	Description
LIN TX	10	LIN transmit
LIN RX	3	LIN receive
LIN CS	46	LIN chip select (active high)
LIN FAULT	9	LIN fault detection
CAN TX	11	CAN transmit
CAN RX	12	CAN receive
LED R	39	Onboard red LED
LED G	38	Onboard green LED
LED B	40	Onboard blue LED

Message Translation

Button Press Translation (LIN → CAN)

LIN Event	LIN ID	LIN Data	→	CAN ID	CAN Data
Driver Heat Press	0xC4	0x41, 0xFF	→	0x302	[0, 2, 16, 0, 8, 0, 0, 0]
Driver Vent Press	0xC4	0x11, 0xFF	→	0x302	[0, 2, 64, 0, 8, 0, 0, 0]
Passenger Heat Press	0x80	0x88, 0xFF	→	0x302	[0, 2, 0, 4, 8, 0, 0, 0]
Passenger Vent Press	0x80	0xA0, 0xFF	→	0x302	[0, 2, 0, 16, 8, 0, 0, 0]

Intensity Control Translation (CAN → LIN)

CAN ID 0x31E carries both driver (D0) and passenger (D1) states simultaneously:

Driver States (D0):

• 0 = Off → LIN 0xB1: [0x0C, brightness]
• 1-3 = Heat Low/Med/High → LIN 0xB1: [0x1C/0x2C/0x3C, brightness]
• 4/8/12 = Vent Low/Med/High → LIN 0xB1: [0x4C/0x8C/0xCC, brightness]

Passenger States (D1):

• 64 = Off → LIN 0x32: [0x09, brightness]
• 65-67 = Heat Low/Med/High → LIN 0x32: [0x49/0x89/0xC9, brightness]
• 68/72/76 = Vent Low/Med/High → LIN 0x32: [0x19/0x29/0x39, brightness]

Backlighting Translation (CAN → LIN)

CAN ID 0x2FA byte 2 (range: 0-200 decimal) is passed directly to LIN messages as the second byte.

Diagnostic LED Indicators

Color	Meaning
Green	Normal operation (idle)
Cyan flash	CAN message received
Magenta flash	Button press detected
Yellow	Initialization in progress
Red	Error state

Troubleshooting

No button detection

• Verify LIN connections and CS pin (should be HIGH)
• Check Serial Monitor for LIN polling activity

LEDs not responding to vehicle commands

• Verify CAN bus connection and termination
• Check Serial Monitor for CAN RX messages on IDs 0x31E and 0x2FA

CAN messages not sent

• Check CAN bus initialization status
• Verify CAN TX/RX pins and bus speed (125 kbps)

License

This project is licensed under the Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License.

You are free to:

• Share — copy and redistribute the material in any medium or format
• Adapt — remix, transform, and build upon the material

Under the following terms:

• Attribution — You must give appropriate credit
• NonCommercial — You may not use the material for commercial purposes
• ShareAlike — Derivatives must use the same license

See the LICENSE file for the full license text.

Acknowledgments

• Georg Icking for the LIN_master_portable_Arduino library
• sorek (handmade0octopus) for the ESP32-TWAI-CAN library
• SK Pang Electronics for the ESP32-S3 CAN & LIN Bus Board
• Claude Code (Anthropic) for development assistance

Author

Projects In Motion, 2025