TrailCurrent Bearing

GNSS (Global Navigation Satellite System) module for precise positioning, timing, and navigation. Part of the TrailCurrent open-source vehicle platform.

Project Overview

TrailCurrent Bearing is a standalone GNSS module that utilizes the DFRobot Gravity GNSS receiver. The data that comes in is formatted and sent over the CAN bus for other modules to use.

Example Use Cases:

• Digital clocks with precise time synchronization
• Navigation and geolocation devices
• Geospatial macros that control devices based on pinned locations
• Vehicle tracking and positioning systems

Hardware Overview

• Function: Precision GNSS receiver with CAN bus interface
• Key Features:
  • DFRobot Gravity GNSS receiver supporting multiple satellite systems
  • CAN bus output for integration with TrailCurrent ecosystem
  • Flexible GNSS mode selection (GPS, BeiDou, GLONASS, combinations)
  • Hierarchical schematic design (5 sheets) for system modularity
  • Power management and signal conditioning

Hardware Requirements

Components

• GNSS Receiver:

  • DFRobot Gravity GNSS module with multi-constellation support

• Microcontroller:

  • ESP32 or equivalent for CAN interface and data processing

• Power Management:

  • Buck converter for regulated power supply

• Interface:

  • CAN transceiver for CAN bus communication
  • JST XH connectors for power and signal distribution

KiCAD Library Dependencies

This project uses the consolidated TrailCurrentKiCADLibraries.

Setup:

# Clone the library
git clone git@github.com:trailcurrentoss/TrailCurrentKiCADLibraries.git

# Set environment variables (add to ~/.bashrc or ~/.zshrc)
export TRAILCURRENT_SYMBOL_DIR="/path/to/TrailCurrentKiCADLibraries/symbols"
export TRAILCURRENT_FOOTPRINT_DIR="/path/to/TrailCurrentKiCADLibraries/footprints"
export TRAILCURRENT_3DMODEL_DIR="/path/to/TrailCurrentKiCADLibraries/3d_models"

See KICAD_ENVIRONMENT_SETUP.md in the library repository for detailed setup instructions.

Opening the Project

1. Set up environment variables (see Library Dependencies above)
2. Open KiCAD:

   kicad /path/to/EDA/trailcurrent-gps-module/trailcurrent-gps-module.kicad_pro

3. Verify libraries load - All symbol and footprint libraries should resolve without errors
4. Navigate hierarchical sheets:
   • Main sheet links to sub-modules for power management, GNSS interface, CAN interface, etc.
   • Each sheet is self-contained but references consolidated library components
5. View 3D models - Open PCB and press Alt+3 to view the 3D visualization
   • All 3D models should load from the consolidated library path
   • Models use relative ${TRAILCURRENT_3DMODEL_DIR} references

Firmware

See src/ directory for PlatformIO-based firmware implementing CAN bus communication and GNSS data processing.

Setup:

# Install PlatformIO (if not already installed)
pip install platformio

# Build firmware
pio run -d /path/to/project

# Upload to board
pio run -t upload -d /path/to/project

GNSS Modes

The DFRobot Gravity receiver supports multiple satellite constellation configurations:

• Mode 1: GPS only
• Mode 2: BeiDou only
• Mode 3: GPS + BeiDou
• Mode 4: GLONASS only
• Mode 5: GPS + GLONASS
• Mode 6: BeiDou + GLONASS
• Mode 7: GPS + BeiDou + GLONASS (Maximum constellation)

Configure the desired mode in firmware initialization. Multi-constellation modes provide better coverage, especially in urban canyons and challenging environments.

Manufacturing

• PCB Files: Ready for fabrication via standard PCB services (JLCPCB, OSH Park, etc.)
• BOM Generation: Export BOM from KiCAD schematic (Tools → Generate BOM)
• JLCPCB Assembly: This project supports automated assembly using JLCPCB
  • See BOM_ASSEMBLY_WORKFLOW.md for detailed assembly workflow
  • Component library includes LCSC, Mouser, and DigiKey part numbers for flexible sourcing

Project Structure

• EDA/trailcurrent-gps-module/ - KiCAD schematic (5 sheets) and PCB design files
  • Main module sheet with sub-sheet references
  • Power management circuit
  • GNSS interface circuit
  • CAN interface circuit
  • Support circuits (regulators, filtering, etc.)
• src/ - Firmware source code for GNSS data processing and CAN interface
• lib/ - Custom libraries and dependencies
• include/ - Header files

Documentation

• Main Schematic: EDA/trailcurrent-gps-module/trailcurrent-gps-module.kicad_sch (with 5 sheet hierarchy)
• PCB Layout: EDA/trailcurrent-gps-module/trailcurrent-gps-module.kicad_pcb

License

MIT License - See LICENSE file for details

This is open source hardware. You are free to use, modify, and distribute these designs for personal or commercial purposes.

Contributing

Improvements and contributions are welcome! Please submit issues or pull requests to the main repository.

Support

For questions about:

• KiCAD setup: See KICAD_ENVIRONMENT_SETUP.md
• Library consolidation: See CONNECTOR_CONSOLIDATION_SUMMARY.md
• Assembly workflow: See BOM_ASSEMBLY_WORKFLOW.md