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The BlueBus hardware design is open-source and available for review, modification, and manufacturing. The schematics and board layouts are provided in industry-standard EAGLE format.

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Design files

BlueBus hardware designs are organized by version, with both schematic and board layout files available.

Hardware v1

Initial production hardware design with core functionality

Hardware v2

Current production design with improved audio chain and features

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File locations

All hardware design files are located in the hardware/ directory of the source repository: 
hardware/
├── v1/
│   ├── BlueBus.sch    (Schematic)
│   └── BlueBus.brd    (Board layout)
└── v2/
    ├── BlueBus.sch    (Schematic)
    └── BlueBus.brd    (Board layout)
The design files use Autodesk EAGLE format (.sch for schematics, .brd for board layouts). You can view and edit these files using EAGLE or other compatible tools.

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Design tool

The schematics are created and maintained using Autodesk EAGLE (Easily Applicable Graphical Layout Editor).

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Opening the schematics

You can view and edit the BlueBus schematics using:
  • Autodesk EAGLE (Free, Standard, or Premium versions)
  • Fusion 360 with EAGLE integration
  • Compatible third-party viewers
EAGLE’s free version is sufficient for viewing and making modifications to the BlueBus design files.

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Online viewing

You can view the BlueBus hardware design online without installing any software:

CADLAB.io

View the BlueBus project on CADLAB.io for online schematic browsing and version history
CADLAB.io provides:
  • Interactive schematic viewer
  • Board layout visualization
  • Revision history and changes
  • Diff views between versions
  • No software installation required

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Key design sections

The BlueBus schematics are organized into functional sections:

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Power supply

  • 12V vehicle power input and protection
  • 5V and 3.3V regulated supplies
  • Power sequencing and filtering
  • Reverse polarity protection

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Microcontroller section

  • PIC24FJ1024GA606 with supporting circuitry
  • Crystal oscillator
  • Reset circuitry
  • Programming header (ICSP)
  • Decoupling capacitors

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Bluetooth module

  • BM83 module integration
  • I2S audio connections
  • UART control interface
  • Antenna matching network
  • Status LED connections

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I-Bus interface

  • TH3122.4 transceiver circuit
  • I-Bus connector pinout
  • Protection components
  • Wake-up circuitry

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Audio outputs

  • PCM5122 DAC circuit
  • DIT4096 S/PDIF encoder
  • PAM8406 amplifier circuit
  • Output connectors and protection
  • Audio filtering and coupling

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USB interface

  • FT231XS USB to UART bridge
  • USB connector
  • ESD protection
  • Configuration resistors

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Board layout

The board layout files (.brd) contain:
  • Component placement and routing
  • PCB layer stackup (typically 2 or 4 layer)
  • Trace widths and impedances
  • Ground plane design
  • Mounting holes and mechanical dimensions

Board size

Compact form factor designed to fit behind vehicle dash panels

Connector placement

Connectors positioned for easy access and cable routing

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Manufacturing

The board layout files are production-ready and can be submitted to PCB manufacturers.

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Manufacturing specifications

ParameterTypical Value
Board Thickness1.6 mm
Copper Weight1 oz (35 µm)
Minimum Trace0.15 mm
Minimum Spacing0.15 mm
FinishENIG or HASL
Solder MaskGreen (standard)
SilkscreenWhite
The design follows standard PCB manufacturing capabilities and doesn’t require advanced processes.

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Design modifications

The open-source nature of the project allows you to modify the hardware:

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Making changes

  1. Clone or download the hardware design files
  2. Open the appropriate version (.sch and .brd) in EAGLE
  3. Make your modifications
  4. Run design rule check (DRC)
  5. Generate manufacturing files (Gerbers)

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Design rules

The board layout includes design rule files specific to the intended manufacturer. Always run DRC before manufacturing to ensure your changes comply with the manufacturing capabilities.
If you make improvements or modifications, consider contributing them back to the project through a pull request.

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Bill of materials

While not stored as separate files, you can generate a BOM (Bill of Materials) from the schematic files using EAGLE’s built-in BOM generation tools. The BOM includes:
  • Part designators (R1, C2, U3, etc.)
  • Component values
  • Package types
  • Manufacturer part numbers (in component attributes)
  • Quantity needed

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Assembly

The board layouts use surface-mount components (SMD) that require appropriate assembly equipment:
  • Solder paste stencil application
  • Pick-and-place machine (or manual placement)
  • Reflow oven or hot air rework station
  • Optional: Wave soldering for through-hole components
Most PCB manufacturers offer assembly services and can populate the boards using the provided design files and BOM.

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Licensing

The hardware design files are open-source and available under the terms specified in the project license. This allows you to:
  • Study the design
  • Manufacture boards for personal use
  • Modify and improve the design
  • Share modifications with the community
Check the project’s LICENSE.md file for specific licensing terms and conditions.

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