We talk with Tobias Kästner, a physicist-turned-software-architect and technical consultant at Inovex, about his journey from painfully slow hardware-software integration cycles to achieving three-week hardware sprints. Tobias shares hard-won lessons from medical device development, where fuzzy requirements and constant feedback from life scientists forced his team to rethink traditional approaches.

The conversation centers on practical techniques: breaking monolithic PCB designs into modular "feature boards" connected via shields (think Arduino-style), using Git for hardware version control with SHA-1s printed on silkscreens, and leveraging tools like Zephyr RTOS to enable plug-and-play firmware that matches the modularity of the hardware. Tobias explains how relaxing constraints like board size and using automation to merge schematics allowed his team to iterate rapidly while maintaining a clear path to final form-factor designs. We discuss how this approach scaled to projects with 120+ people across multiple teams, and why the interplay between system architecture, organizational structure, and information flow matters more than most realize.

"When the board arrived, not a single line of code had been written for it because no one had been able to touch it. It took us nine additional months to debug all the things out of it." — Tobias Kästner

"I've never seen any board working the first time. I've never seen any prototype without thin wires patching things out, but that's maybe a different story." — Tobias Kästner

"We cannot think these architectures as independent of one another. If we have limitations in two of these architectures, we will see these limitations in the third architecture as well." — Tobias Kästner

Through Inovex, Tobias provides trainings for both Zephyr and Yocto Linux, as well as consultancy and engineering support for embedded projects -- from 1-2 day workshops evaluating architectural state and cost/benefit analysis, to first prototypes, to full-fledged software development. With partners such as alpha-board (Berlin) and Blunk electronic (Erfurt), they also offer agile hardware services and help teams get started with the methods discussed in this episode.

Companies:

Talks and publications:

Books recommended by Tobias:

You can find Jeff at https://jeffgable.com.
You can find Luca at https://luca.engineer.

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