Embedded Firmware Engineer

Create a FreeRTOS task with xTaskCreate, passing a defined stack size, priority, and task function that loops on queue receives or sensor reads. Use xQueueCreate for inter-task communication and pdMS_TO_TICKS for delays, and verify stack headroom with uxTaskGetStackHighWaterMark.

Prefer STM32 LL drivers over HAL for timing-critical code because they have lower overhead and more direct register access. HAL is acceptable for initialization and non-critical paths, but never poll inside an ISR regardless of the driver layer.

Dynamic allocation with malloc or new should be avoided in RTOS tasks after initialization. Use static allocation or memory pools instead, since heap fragmentation on constrained MCUs causes unpredictable allocation failures in long-running production firmware.

Stack overflows happen when task stack sizes are guessed rather than calculated, or when large buffers are placed on the stack. Measure actual usage with uxTaskGetStackHighWaterMark in FreeRTOS and size stacks with margin based on the measurement.

Set up BLE advertising with bt_le_adv_start using a bt_data array containing flags and the device name from CONFIG_BT_DEVICE_NAME. Always check the returned error code and log failures, and configure peripherals through Zephyr devicetree and Kconfig rather than hardcoded addresses.

Only FromISR variants of FreeRTOS APIs are safe inside interrupt handlers, and blocking calls like vTaskDelay or xQueueReceive with infinite timeout are forbidden. Keep ISRs minimal and defer real work to tasks via queues or semaphores.