We are seeking an experienced embedded systems engineer or IoT hardware developer to design and develop a low-cost, modular STM32-based IoT device for advanced asset tracking and environmental monitoring. The device should include multi-sensor data collection, 5G connectivity, full GPS tracking, and many features. Develop a reliable, battery-powered IoT device capable of: Real-time GPS tracking Environmental monitoring Motion and tilt detection 5G data transmission Remote configuration & OTA updates Minimum 20-day battery life MCU STM32 (low-power series preferred: STM32L / STM32U) Secure boot support External flash for data logging Connectivity 5G cellular modem (LTE fallback acceptable if justified) Nano SIM or eSIM support WiFi (2.4 GHz minimum) Bluetooth BLE 5.0+ GNSS (GPS + GLONASS preferred) Sensors Internal temperature sensor External thermocouple support Humidity sensor Pressure sensor 3-axis accelerometer Tilt detection Motion detection Shock/vibration detection Battery level monitoring Power Rechargeable battery Minimum 20 days operation per charge Ultra-low power sleep modes Motion-based wake-up Battery health monitoring Advanced Tracking Features Device must support: Real-time GPS tracking Geofencing (multiple zones) Location history logging Movement-based tracking intervals Tamper detection Impact detection Speed alerts Idle alerts Temperature threshold alerts Data buffering when offline Heartbeat/status reporting Secure TLS communication Remote configuration OTA firmware updates Firmware Requirements Modular and scalable architecture FreeRTOS (preferred) OTA firmware update capability Secure bootloader Remote configuration of: Reporting intervals Sensor thresholds Alert settings Well-documented source code Git repository delivery Designed for future feature expansion Communication Protocols MQTT over TLS HTTPS REST API JSON-based payload Cloud-ready (AWS IoT / Azure IoT compatible) Hardware Design Expectations Low BOM cost Production-ready PCB design Modular sensor expansion capability Compact industrial enclosure Designed for manufacturability (DFM) Option for external antenna Deliverables Complete schematic & PCB files Optimized BOM with cost breakdown Fully functional firmware source code Secure bootloader + OTA implementation Prototype units (if part of agreement) Technical documentation Testing & validation report