bac-hardware/sbc/cm5-carrier-board/README.md

MCU Carrier Board – CM5-Compatible (Single bacBus)

Subsystem: MCU
Status: ✅ Released

Latest Release:

• Version: v1r1
• Date: 2025-04-03
• KiCad: v9

Overview

This board is a respin of the CM5 MINIMA Rev2 by Pierluigi Colangeli, adapted to fit within the Build a CubeSat structure. It accepts a Raspberry Pi Compute Module 4 or 5 and provides a Key-M M.2 slot for 2230/2242 PCIe cards. Both CSI camera connectors are available, as well as 10/100 Ethernet via PicoBlade (for use with BotBlox switches) and USB 2.0 via USB-C.

The board integrates into the system using a single bacBus bus and is intended as a compact, flexible CubeSat payload computer.

Please consider starring CM5 MINIMA and supporting Pierluigi for his foundational work.

Respin Changelog

1. Deletions

• 1x USB-C
• HDMI
• IO:
  • SPI conn
  • I2C conn
  • Power LED
  • Env sensor
• PCI-E 3v3 buck converter

2. Changes

• Move CSI0 further left
• Extend M.2 to 2242
• Passives: 0402 -> 0603
• Horizontal USB-C conn
• M3 solder nuts
• Switches -> jumper pads

3. Additions

• CSI1
• PicoBlade for ethernet (instead of RJ45)
• CAN controller/transceiver: MCP251863T-H/SS
• Power multiplexing
• 2 current sensors: INA260
• bacBus M.2 connectors: MDT350M01001VT
• IMU: BNO086

Specifications

• Dimensions: 85 mm × 85 mm
• Layer Count: 6
• Panelization: No
• Mounting: Via rails or M3 bolts
• Stacking: bacBus connection on Xp side only, top and bottom.

Connectors & Interfaces

• Compute Module: Raspberry Pi CM4 or CM5
• Expansion Slot: Key-M M.2 2230/2242 (PCIe)
• USB: USB-C for data + power
• Ethernet: 10/100 via PicoBlade
• Camera: Dual CSI camera connectors
• bacBus: System connection for power, I2C, and CAN

Files

• Design files: Located in the kicad9/ folder
• Schematics: PDF
• 3D Render:
  

Manufacturing

• Release: sbc-cm5-carrier-board-v1r1
• BOM: Included
• Instruction:
  • Ordering: Included (PCBWay)
  • Sourcing: Not Included
  • Assembly: Not Included

Notes

This board is intended for development and test environments including high-altitude ballooning. Not spaceflight-rated.

Acknowledgments

Adapted from CM5 MINIMA Rev2 by Pierluigi Colangeli – many thanks to Pier for sharing his excellent work and providing guidance on this respin.

Known Bugs and Limitations

• No onboard 3.3 V rail for PCIe – must be supplied externally when EPS is not connected
• USB breakout not yet implemented
• Single bacBus connection
• Additional GPIO and interfaces could be broken out
• No coin cell backup battery for RTC

Ongoing Testing Results

Untested

• Ethernet via PicoBlade
• M.2 Slot
• CAN

Working

• The CM5 :]
• Both CSI

Not Working

• IMU - bad clock?

License

This PCB is licensed under CERN-OHL-S-2.0 in accordance with the upstream CM5 MINIMA REV2 project.

Contributing

Contributions to the Build a CubeSat hardware ecosystem are highly appreciated! To keep things structured, here’s how you can contribute:

Fixes & Improvements to Existing Designs

1. Create a new feature branch (git checkout -b feature/your-feature-name)
2. Commit your changes (git commit -m 'Brief description of change')
3. Push to the branch (git push origin feature/your-feature-name)
4. Submit a Pull Request (PR) with a clear description of the changes

New Designs & Community Contributions

• Create your own repository
• Share a link in community discussions or open an issue
• If relevant, it’ll be referenced in the docs 🙌

Supporting This Project

• Patreon
• KoFi
• PayPal