Ying Zhang worked on the telink-semi/zephyr repository, focusing on embedded systems and Bluetooth functionality using C within an RTOS environment. During this period, Ying addressed a critical issue affecting BLE initialization by correcting the definition of the ctr_lock mutex in the random_ctr_drbg.c module. This fix ensured that the sysworkq task could reliably acquire the mutex during Bluetooth startup, restoring proper BLE operation. The work demonstrated a solid understanding of concurrency and synchronization in embedded software, resolving a subtle bug that impacted system reliability. Although no new features were added, the depth of the fix contributed to robust Bluetooth performance.