Building big systems with remote hardware teams

Early in our company’s history, the team built out a development platform, named the Gemini Bring-up board, representing the core of the embedded design for our product-- our Gemini complex (Service Processor + Root of Trust
Management Network plane). The resulting platform was a very nice development tool, with hilarious silkscreen and some awesome ideas that have continued informing current and future designs, but we rapidly outgrew this first design. While the major choices held, such as which microcontrollers are present, the still-nebulous design of the actual product, and subsequent design iteration, left the periphery of the bring-up board bearing little resemblance to the final Gemini complex design. The changes came from a variety of unforeseen sources: the global chip shortage forced BOM changes and a better understanding of the constraints/needs of our product necessitated architecture changes, resulting in further drift between this platform and what we intended to implement in the product.

First custom Oxide hardware with SP and RoT

A re-imagining of what would be most useful gave way to the Gimletlet, a major work-horse for in-house development, designed (and initially hot-plate reflowed) by Cliff. The Gimletlet is essentially a development board using the STM32H7 part that we’re using as our Service Processor (SP) in our product. It provides power and basic board functionality including a couple of LEDs, and a dedicated connector for a network breakout card, and breaks out most of the remaining I/O to PMOD-compatible headers. This choice has been key to enabling a very modular approach to prototyping, recognizing that less is more when it comes to platforms. The Gimletlet design means that we can build purpose-built interface cards without needing to worry about network connectivity or processor support, simplifying the design of the interface cards and able to share a core board support package.

Custom STM32H7 board with I/O breakout to many PMOD interfaces

Our team has learned that modularity is key to making these small proto-boards successful. It does mean workspaces can get a little messy with a bunch of boards connected together, but we’ve found this to be a good balance, allowing our team members to cobble together a small, purpose-built system that meets their specific needs, and allows us to easily share these common, low-cost setups to our distributed team. The modularity also means that storing them is relatively easy as they can be broken down and stashed in small boxes.

Gimletlet with Igntionlet, SPI MUx, Dimmlet, RoTCarrierCarrier, and RoTCarrier connected

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