Explore the fascinating journey of porting the Zephyr operating system to a hearing aid in this 36-minute conference talk. Delve into the challenges and solutions encountered when adapting Zephyr for a life-changing medical device that operates with minimal power and space while being produced in millions. Learn about molding Zephyr to support exotic development environments, including FDA-approved medical devices. Discover the intricacies of making Zephyr a modular component, porting it to a custom processor, ensuring endianness portability for the Bluetooth stack, supporting proprietary toolchains, and enhancing tracing infrastructure. Gain insights into the unique aspects of hearing aid technology, custom tools, toolchain abstraction, out-of-tree code management, and Oticon's contributions to the Zephyr project. Understand the future directions and potential applications of this innovative integration of open-source technology in medical devices.