Candlelight GNX - CAN FD Interface

A stylish CAN FD interface device shaped like the iconic Buick GNX, combining classic automotive aesthetics with modern CAN bus functionality.

Overview

The Candlelight GNX is a clone of the popular candlelightfd CAN FD interface, reimagined in the distinctive silhouette of the legendary Buick Grand National GNX. This USB-to-CAN adapter provides CAN bus communication capabilities while paying homage to one of the most iconic performance cars of the 1980s.

Front view of the Candlelight GNX

Back view showing the USB-C connector and CAN terminal

Features

🚗 CAN Bus Support

• CAN 2.0A/2.0B - Classic CAN protocol support
• CAN FD - CAN with Flexible Data-rate for higher bandwidth applications
• High-speed CAN transceiver (TJA1051T-3) for robust communication
• Screw terminal connector for easy CAN H/L wiring

🔌 Modern Connectivity

• USB-C interface for reliable power and data connection
• USB 2.0 Full Speed communication
• Plug-and-play compatibility with existing CAN tools

⚡ Power & Status

• 3.3V LDO regulator (MCP1754S) for clean power supply
• Power LED - Visual confirmation of device power
• TX/RX LEDs - Real-time indication of CAN traffic
• USB powered - No external power supply needed

🔧 Advanced Features

• DFU (Device Firmware Update) - Field-upgradeable firmware via USB
• Piezo buzzer - Audio feedback for diagnostics and alerts (plays "Not Like Us" on boot)
• SWD programming interface - For development and debugging
• STM32G0B1CBT6 microcontroller - ARM Cortex-M0+ with CAN FD support

Hardware Specifications

Component	Part Number	Description
Microcontroller	STM32G0B1CBT6	ARM Cortex-M0+, 128KB Flash, CAN FD
CAN Transceiver	TJA1051T-3	High-speed CAN transceiver with VIO pin
Voltage Regulator	MCP1754S-3302	3.3V, 150mA LDO regulator
Clock Source	MAX7375AXR805	8MHz silicon oscillator
USB Connector	USB-C	16-pin horizontal mount receptacle

Firmware

The Candlelight GNX uses the open-source candleLight firmware with CAN FD support.

Firmware Repository

https://github.com/raulperdomo/candleLight_fw.git
Branch: topic/candleLightFD

Flashing Instructions

1. Enter DFU Mode: The software will automatically jump to DFU mode when running. The BOOT0 jumper (J1) is only needed if the software gets corrupted.
2. Flash the firmware using dfu-util:

   sudo dfu-util -D candleLightFD_fw.bin -a 0 -s 0x08000000

3. Reset the device to begin normal operation

Prerequisites

• dfu-util installed on your system
• candleLightFD firmware binary (.bin file)

Usage

1. Connect the USB-C cable to your computer
2. Wire your CAN bus to the screw terminal (CAN H, GND, CAN L)
3. Install appropriate drivers if needed (most modern systems have built-in support)
4. Use with your favorite CAN analysis software:
   • SocketCAN (Linux)
   • PCAN-View (Windows)
   • SavvyCAN
   • CANoe/CANalyzer
   • And many others supporting candleLight protocol

LED Indicators

• Power LED (Red) - Device is powered and operational
• TX LED (Green) - Transmitting CAN frames
• RX LED (Blue) - Receiving CAN frames

Pin Configuration

CAN Terminal (J2)

Pin	Function
1	CAN H
2	GND
3	CAN L

SWD Debug (J3) - 10-pin Cortex Debug Connector

Standard ARM SWD interface for development and debugging.

BOOT0 Jumper (J1)

Pin	Function
1	BOOT0
2	GND

Short these pins together while connecting USB to force the device into DFU (Device Firmware Update) mode. This is only needed if the software gets corrupted and cannot automatically enter DFU mode.

CAN Termination (J4)

Jumper to add 120Ω termination resistor between CAN H and CAN L. Install jumper if this device is at the end of the CAN bus network.

Compatibility

The Candlelight GNX is compatible with:

• Linux - Native SocketCAN support
• Windows - candleLight drivers
• macOS - Third-party CAN software
• Embedded systems - Any system supporting USB CAN adapters

Development

This is an open-source hardware project. The KiCad design files are available in this repository.

Project Files

• Defcon_33.kicad_pro - Main project file
• Defcon_33.kicad_sch - Schematic design
• Defcon_33.kicad_pcb - PCB layout
• Defcon_33.xml - Netlist export

License

Hardware design is open source. Please refer to the firmware repository for firmware licensing terms.

Tribute

This project pays homage to the 1987 Buick Grand National GNX, one of the most feared muscle cars of its era. Just as the GNX dominated the streets with its turbocharged performance, the Candlelight GNX aims to dominate your CAN bus analysis needs with style and reliability.

The boot sound is a nod to Kendrick Lamar, with the buzzer playing "Not Like Us"

"All I ever wanted was a black Grand National" - Kendrick Lamar (tv off)

"We never stop pulling... until we're there." - GNX Commercial, 1987