September 2025 monthly summary focused on delivering hardware integration improvements and maintainability gains for Ethos-U workloads in Zephyr. The month delivered two major items: cleanup in Numaker driver to align with Ethos-U core changes and expanded board support plus sample organization to streamline developer workflows. These efforts reduce configuration complexity, enhance hardware compatibility, and improve the end-to-end model deployment path.

Month: 2025-08 | zephyr-testing repository: Key features delivered: - Ethos-U DCache management integration: added support for default data cache (dcache) flush and invalidate operations for the Ethos-U driver. This feature can be optionally disabled by the user if they provide their own dcache management functions. Introduced a new Kconfig option and implemented the dcache functions using Zephyr's system cache utilities. Commit: 1bc008dae398b425bb4f816b7811bc5f71233c51. - Enhanced USB UDC logging for debuggability: refined logging in the USB UDC driver to improve issue diagnosis. Logs now include the memory address of allocated network buffers for successful allocations and endpoint information for failures. Commit: cfa837c6dd14a99dd90299e748da9eacc6d90392. - Numaker USB device controller ISR refactor: refactored the large ISR into smaller, dedicated functions for plug/unplug, wakeup, reset, suspend, resume, SOF, Setup, and endpoint events to improve code organization and maintainability. Commit: 13315d1ea09b0443f1e3f17ee5235aebc34d90d1. Major bugs fixed (through these changes): - Clarified logging for USB UDC allocation paths to reduce debugging time and misdiagnosis of allocation issues. - Reduced regression risk in USB ISR by modularizing the handler, enabling targeted testing and easier future enhancements. Overall impact and accomplishments: - Substantial improvements in system stability and debuggability for Ethos-U and USB subsystems. - Enhanced maintainability of USB driver codebase through modular ISR design and clearer logs, enabling faster future iterations. - Strengthened integration points with Zephyr kernel (Kconfig options and system cache utilities) to provide flexible and robust configurations for end users. Technologies/skills demonstrated: - C, embedded systems development within Zephyr RTOS - Driver development for Ethos-U and USB controllers - Cache management integration using Zephyr system cache utilities - Kconfig-based feature enablement and configurability - Code refactoring for ISR modularization and improved maintainability - Debugging and logging best practices for driver diagnostics

In July 2025, contributed targeted changes to the zephyr-testing repository to stabilize USB Device Controller (Numaker) behavior and improve code clarity. Addressed a clang-format-induced regression affecting interrupt enable handling and endpoint assignment, and simplified ISR code by removing unnecessary volatile qualifiers. The work reduces runtime risk, improves USB reliability, and enhances maintainability of the USB stack.

June 2025 monthly summary: Focused on stability and reliability in AmbiqZephyr's networking and serial subsystems. Delivered ESP AT Wi-Fi driver fixes to reduce premature socket releases, deadlocks in socket close path, reference-counting issues with rx_sock, and CIPRECVDATA parsing for AT 1.7; added hardware flow control for the Numaker serial driver via Device Tree with a configurable timeout for AT+CIPSEND in TCP sockets; and updated MAINTAINERS to add a hal_ethos_u collaborator. These changes improve production readiness, software robustness, and maintenance efficiency, enabling more reliable IoT deployments and easier collaboration on low-level driver development.

May 2025: Delivered a set of core platform enhancements for AmbiqZephyr on the Nuvoton M55M1x, expanding hardware support, improving configurability, and enabling new workloads. Implemented USB device controller support, board-level button inputs, and MVE acceleration, plus ESP8266 shield integration. Resolved a critical Ethos-U NPU config override issue to ensure reliable NPU configuration overrides. The work improves product readiness across boards, reduces integration effort for customers, and increases the range of DSP/ML workloads that can run on the platform.

April 2025 monthly summary for AmbiqZephyr: Focused on expanding CAN-FD capabilities and improving reliability for CAN devices across supported SoCs. Key outcomes include delivering Nuvoton m55m1x CAN-FD support and stabilizing CAN-FD core clock logic for m2l31x. This work enhances product readiness, reduces integration effort, and strengthens the CAN subsystem's robustness.

March 2025 monthly summary focusing on key outcomes for zephyrproject-rtos/zephyr. Delivered a critical safety fix in the tflite_ethosu sample by replacing unsafe dynamic thread stack allocation with a static stack using K_THREAD_STACK_DEFINE, addressing issues with raw buffer usage. This change, tracked under commit 9f58227bf19c15497f1d9be3dc8afedbddb8afe0, improves memory safety, stability, and portability of the sample across devices. Key achievements: - Fixed unsafe thread stack allocation in tflite_ethosu sample; replaced dynamic memory with static stack using K_THREAD_STACK_DEFINE (commit 9f58227bf19c15497f1d9be3dc8afedbddb8afe0). - Improved memory safety and runtime stability by aligning with Zephyr threading best practices for sample code. - Strengthened maintainability and reviewability of the sample by adopting a robust, documented pattern for thread stack definition.