
Cheng Chang developed and enhanced Bluetooth protocol features and reliability across multiple Zephyr-based repositories, including AmbiqMicro/ambiqzephyr, zephyrproject-rtos/zephyr, and nrfconnect/sdk-zephyr. He built comprehensive test suites for Bluetooth Classic L2CAP and A2DP, implemented protocol compliance fixes, and improved error handling and diagnostics. Using C, Python, and embedded systems expertise, Cheng addressed interoperability issues, reduced compiler warnings, and strengthened unit testing infrastructure. His work included targeted bug fixes for mobile connectivity and concurrency, as well as robust validation and configuration improvements. These contributions deepened automated test coverage and improved Bluetooth stack stability for cross-platform embedded applications.
March 2026: Delivered comprehensive A2DP Bluetooth test suites for sink and source in nxp-upstream/zephyr, substantially improving automated validation for Bluetooth Classic flows. Implemented end-to-end test coverage including endpoint registration, connection lifecycle, capability discovery, and lifecycle operations (open, start, suspend, close) with scenarios in both directions to ensure interoperability with a Bumble peer. The work enables reliable regression testing, faster integration, and better risk reduction for A2DP features. The implementation is backed by focused commits that added both suites and the associated tests for sink and source roles.
March 2026: Delivered comprehensive A2DP Bluetooth test suites for sink and source in nxp-upstream/zephyr, substantially improving automated validation for Bluetooth Classic flows. Implemented end-to-end test coverage including endpoint registration, connection lifecycle, capability discovery, and lifecycle operations (open, start, suspend, close) with scenarios in both directions to ensure interoperability with a Bumble peer. The work enables reliable regression testing, faster integration, and better risk reduction for A2DP features. The implementation is backed by focused commits that added both suites and the associated tests for sink and source roles.
Monthly summary for 2025-12 focusing on key accomplishments and business impact for nrfconnect/sdk-zephyr. Delivered a critical reliability fix for Bluetooth mobile connectivity by aligning MOPL with MTU when MOPL exceeds MTU, preventing mobile device connection failures and improving user experience on iPhone and Android. The change is implemented as a bug fix under the Bluetooth host/obex stack with commit abb707ca3695ee00fec96c69d8ac966d164828ee. This work enhances cross-platform compatibility and reduces support friction, contributing to more stable Bluetooth operations in mobile contexts.
Monthly summary for 2025-12 focusing on key accomplishments and business impact for nrfconnect/sdk-zephyr. Delivered a critical reliability fix for Bluetooth mobile connectivity by aligning MOPL with MTU when MOPL exceeds MTU, preventing mobile device connection failures and improving user experience on iPhone and Android. The change is implemented as a bug fix under the Bluetooth host/obex stack with commit abb707ca3695ee00fec96c69d8ac966d164828ee. This work enhances cross-platform compatibility and reduces support friction, contributing to more stable Bluetooth operations in mobile contexts.
Month: 2025-11 — Focused on reliability and testability for Bluetooth Classic in nrfconnect/sdk-zephyr. Delivered two key changes: (1) OBEX abort concurrency handling fix to ensure correct operation under concurrent requests by validating the active client and rejecting with -EBUSY if a different active client exists; (2) Testing infrastructure enhancement via a STATIC macro to control visibility of static functions for unit testing, enabling testing when CONFIG_ZTEST is enabled without affecting normal builds.
Month: 2025-11 — Focused on reliability and testability for Bluetooth Classic in nrfconnect/sdk-zephyr. Delivered two key changes: (1) OBEX abort concurrency handling fix to ensure correct operation under concurrent requests by validating the active client and rejecting with -EBUSY if a different active client exists; (2) Testing infrastructure enhancement via a STATIC macro to control visibility of static functions for unit testing, enabling testing when CONFIG_ZTEST is enabled without affecting normal builds.
Month: 2025-10 — Zephyr project (zephyrproject-rtos/zephyr). Delivered a targeted bug fix to reduce compiler warnings in the Bluetooth A2DP path by conditionally compiling unused code paths for sink/source delay reporting, aligned with enablement configurations.
Month: 2025-10 — Zephyr project (zephyrproject-rtos/zephyr). Delivered a targeted bug fix to reduce compiler warnings in the Bluetooth A2DP path by conditionally compiling unused code paths for sink/source delay reporting, aligned with enablement configurations.
Month 2025-09 summary focusing on stabilizing Bluetooth L2CAP channel handling in zephyr-testing. Delivered a critical fix for server-role channel retrieval by persisting PSM values in the channel structure, enabling reliable retrieval of channels by PSM. Implemented via two commits addressing the issue 'bluetooth: host: l2cap: fix issue that can't get chan by psm'. Major impact includes improved reliability and maintainability for Bluetooth server components and reduced debugging time for channel lookups, with tests updated accordingly. Technologies/skills demonstrated include C, Bluetooth L2CAP, patch discipline, Git workflows, code review, and testing in Zephyr project.
Month 2025-09 summary focusing on stabilizing Bluetooth L2CAP channel handling in zephyr-testing. Delivered a critical fix for server-role channel retrieval by persisting PSM values in the channel structure, enabling reliable retrieval of channels by PSM. Implemented via two commits addressing the issue 'bluetooth: host: l2cap: fix issue that can't get chan by psm'. Major impact includes improved reliability and maintainability for Bluetooth server components and reduced debugging time for channel lookups, with tests updated accordingly. Technologies/skills demonstrated include C, Bluetooth L2CAP, patch discipline, Git workflows, code review, and testing in Zephyr project.
August 2025 — Zephyr Testing: Delivered notable Bluetooth AVDTP protocol improvements and targeted fixes that strengthen interoperability, error visibility, and reconfiguration robustness in the zephyr-testing repo. A focused commit addressed a command/response format error to improve cross-stack compatibility. These changes reduce configuration errors, improve diagnostics, and advance protocol conformance across platforms.
August 2025 — Zephyr Testing: Delivered notable Bluetooth AVDTP protocol improvements and targeted fixes that strengthen interoperability, error visibility, and reconfiguration robustness in the zephyr-testing repo. A focused commit addressed a command/response format error to improve cross-stack compatibility. These changes reduce configuration errors, improve diagnostics, and advance protocol conformance across platforms.
July 2025 monthly summary for AmbiqMicro/ambiqzephyr focusing on Bluetooth stack hardening and feature enhancements. Delivered robust L2CAP parameter validation, A2DP safety improvements, and expanded configuration error reporting, enhancing stability, debugging clarity, and developer efficiency.
July 2025 monthly summary for AmbiqMicro/ambiqzephyr focusing on Bluetooth stack hardening and feature enhancements. Delivered robust L2CAP parameter validation, A2DP safety improvements, and expanded configuration error reporting, enhancing stability, debugging clarity, and developer efficiency.
June 2025: Delivered a critical Bluetooth AVDTP bug fix in AmbiqMicro/ambiqzephyr to improve interoperability and spec compliance. The change removes LOSC from the set configuration reject response to align with the Bluetooth AVDTP specification, preventing incorrect acceptances during configuration negotiation. The fix is tracked with a concise commit for traceability and low risk to existing flows.
June 2025: Delivered a critical Bluetooth AVDTP bug fix in AmbiqMicro/ambiqzephyr to improve interoperability and spec compliance. The change removes LOSC from the set configuration reject response to align with the Bluetooth AVDTP specification, preventing incorrect acceptances during configuration negotiation. The fix is tracked with a concise commit for traceability and low risk to existing flows.
April 2025 — Delivered a comprehensive Bluetooth Classic L2CAP server test suite in AmbiqMicro/ambiqzephyr, enabling end-to-end validation of connection lifecycle, MTU handling, multi-channel communication, data transfer, and stress scenarios. This work leverages the bumble library for client-side operations and Zephyr L2CAP APIs on the device under test, strengthening regression coverage for the Bluetooth Classic stack.
April 2025 — Delivered a comprehensive Bluetooth Classic L2CAP server test suite in AmbiqMicro/ambiqzephyr, enabling end-to-end validation of connection lifecycle, MTU handling, multi-channel communication, data transfer, and stress scenarios. This work leverages the bumble library for client-side operations and Zephyr L2CAP APIs on the device under test, strengthening regression coverage for the Bluetooth Classic stack.

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