ESSENTIAL DUTIES AND RESPONSIBILITIES: Develop and maintain LoRaWAN module AT command firmware across multiple hardware variantsOwn the LoRaWAN MAC layer library - Class A/B/C operation, multicast, FOTA, ADR, regional parameter complianceImplement and validate LoRaWAN specification compliance including Class B beacon timing, ping-slot scheduling, and multicastPort and maintain Zephyr RTOS board support packages including board definitions, device drivers, and subsystem integrationDevelop custom LoRaWAN sensor applications using Mbed OS and Zephyr RTOS for customer-specific deploymentsBring up and validate new hardware variants and component changes across the product lineDesign and execute comprehensive host-based test suites using CppUTest and Zephyr TwisterMaintain bootloaders and FOTA update infrastructure for secure field updatesOptimize power consumption for battery-operated devices targeting ultra-low-power sleep modesSupport LoRa Alliance technical working group contributions (L2 protocol, payload schema). QUALIFICATION REQUIREMENTS: 5+ years bare-metal and RTOS firmware development on Arm Cortex-M (M0+, M3, M4)Strong C/C++ for resource-constrained MCUs (32KB RAM / 256KB Flash targets)LoRaWAN protocol stack implementation experience (MAC layer, Class A/B/C, regional parameters)STM32 family (STM32L151, STM32L4, STM32U3) - peripherals, low-power modes, HAL/LL driversMbed OS 6.x application development and build systemZephyr RTOS - device tree, Kconfig, west build system, subsystem developmentSPI/I2C peripheral drivers (SX1272/SX1276/SX1262 radio, external flash, EEPROM)JTAG/SWD debugging, logic analyzer, RF test equipmentGit, CI/CD (Jenkins), automated firmware testingAT command interface design and implementation.