Firmware Developer for Custom ESP32 Project

Job Title: Senior Android Engineer (B2B Contract / Remote Vietnam) – IoT & BLE Custom Hardware Company / Project: Premium Cosmetic Hardware Device Location: Remote (Vietnam-based) Contract Duration: 1-Month Sprint (Full-Time, ~120 Hours) Compensation: Competitive Project Rate (USD ) Project Overview: We are developing a premium, commercial cosmetic hardware device built on the Espressif ESP32 platform. The device is powered by an external AC/DC wall adapter and contains an internal high-voltage generator. We require an elite, native Android Freelancer based in Vietnam to engineer a rock-solid, production-grade Bluetooth Low Energy (BLE) communication layer. Because this device operates in an electrically noisy environment with a high-voltage payload, the communication architecture must prioritize safety-critical state machines, EMI data protection, and rapid reconnection profiles. Core Deliverables & Responsibilities: • EMI-Resilient BLE Engine: Design and build the mobile BLE lifecycle (scanning, fast reconnection, state synchronization) in Native Kotlin, ensuring sub-second reconnection if localized high-voltage noise drops the radio link. • Thread-Safe Command Queue: Implement a strictly sequential FIFO command queue using Kotlin Coroutines / Flow or robust frameworks (e.g., Nordic's Android-BLE-Library) to eliminate native Android GATT race conditions. • Data Integrity Verification: Implement packet-level verification (e.g., CRC32 checksums) on custom GATT characteristics to prevent packet corruption caused by high-voltage electromagnetic interference. • Safety Heartbeat / Watchdog: Build a continuous, lightweight background heartbeat loop that continuously signals the app's health to the ESP32. This acts as a critical fail-safe to shut down the high-voltage circuit if the app crashes or disconnects. • Mock Environment Testing: Develop a software-based GATT simulation wrapper on day one to thoroughly test the communication state machines while the physical hardware setup is being finalized. Requirements: • 5+ years of native Android (Kotlin) development experience. • Deep, proven experience shipping production applications that interface with custom BLE/IoT hardware peripherals (Direct experience with ESP32, Nordic, or TI chips is highly advantageous). • Expert understanding of the Android BLE stack, OEM-specific Bluetooth quirks (Samsung, Xiaomi, etc.), and runtime permission structures. • Strong verbal and written English communication skills to collaborate efficiently with our international engineering team. • Comfortable working autonomously on an aggressive 1-month timeline.