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Full Stack & IoT Developer | Kiosk Systems | Mobile Apps | Embedded Solutions I help businesses turn ideas into complete, production-ready products. Instead of hiring separate developers for mobile apps, backend systems, and embedded devices, I provide end-to-end development covering everything from hardware integration to cloud services. Over the past 5+ years, I have built commercial software, IoT products, business systems, kiosk applications, and connected device solutions for startups, companies, and organizations. What I Deliver • Kiosk & Tablet Solutions * Customer feedback systems * Self-service kiosks * Visitor management systems * Android tablet applications * Offline-first business applications * Device management interfaces • Mobile & Cross-Platform Applications * Android and iOS applications * Desktop applications * Internal business tools * Modern, responsive user interfaces • Backend & Cloud Systems * REST APIs * Authentication systems * Admin dashboards * Reporting and analytics * Third-party integrations • IoT & Embedded Development * ESP32 and STM32 firmware * BLE, WiFi, MQTT, LoRaWAN * Serial Port communication * Sensor integration * Hardware-to-cloud connectivity Why Clients Work With Me • One developer responsible for the entire solution • Faster development with fewer communication gaps • Strong understanding of both software and hardware • Clean, maintainable, production-ready code • Transparent communication and reliable delivery Typical projects I work on include kiosk systems, tablet applications, IoT products, industrial monitoring solutions, connected devices, internal business tools, and custom software platforms. Whether you need a prototype, an MVP, or a complete product ready for deployment, I can help transform requirements into a reliable working solution.

I am an Automation system design engineer, Hardware designer, Firmware developer and have the extensive experiences even over 15 years. I'm especially interested in home automation or making intelligent new products or acquire and application new technologies. I work with the target of design to low cost, low power, high performance, the miniaturization of device by a compact layout. I design carefully to achieve the best performance in all projects, I find joy and pride in the successful results of projects. The areas I've experienced a lot are as follows. ● STM32F103RCT6TR, STM32F407VGT6, STM32F429ZIT6, STM32L476RGT6, STM32H743ZIT6, etc. ● ESP32-WROOM-32D, ESP32-WROVER-E, ESP8266, etc. ● nRF51822, nRF52810, nRF52832, nRF52833, nRF52840, nRF52843, etc. ● RAK811, RAK831, RAK3172, RAK4200, etc. ● SIM7000G, SIM7070G, SIM7600E, SIM7600G, etc. ● Arduino Mega2560, Arduino Mega328P, etc. ● SRAM, DDR, DDR2, DDR3, LPDDR3, DDR4, DDR5, LPDDR4, etc. ● MEMS Sensors (3-axis, 6-axis, 9-axis), ECG, PPG, HRM, SPO2, CO, CO2, Humidity and Temperature, Touch, Pressure, PIR, etc. ● PCIe, SATA, Ethernet, HDMI, VGA, LVDS, USB, UART, USART, CAN, SPI, I2C, I2S, RS232C, RS485/RS422, etc. ● BLE, IoT, AWS, GPS, GSM, Bluetooth, Wi-Fi, Z-Wave, Zigbee, LoRa, NFC, RFID, LTE, etc.

I help companies debug, stabilize, and ship embedded products on STM32, ESP32, nRF52, EFR32, NXP KL17, JieLi, HDSC, and other ARM / RISC-V platforms. Typical problems I solve: • STM32 hard faults, crashes, boot issues • Custom board bring-up and peripheral integration • BLE / LoRa / MQTT connectivity issues • RS485 / Modbus communication instability • Low-power optimization for battery-operated devices • OTA reliability issues • Porting firmware to new boards, MCUs, or RTOS platforms • Turning prototypes into production-ready firmware I have 15+ years of embedded development experience across industrial communication systems, low-power IoT devices, wireless products, and mass-production consumer electronics. My background includes product lines with more than 10M devices shipped. Core platforms and technologies: • STM32 / ESP32 / nRF52 / EFR32/ NXP KL17 / JieLi • FreeRTOS / Zephyr / Arduino / PlatformIO • BLE / LoRa / NB-IoT / 4G / Cat.1 • RS485 / Modbus / UART / SPI / I2C • AWS IoT / MQTT / OTA • Battery-powered and ultra-low-power systems Selected experience: • STM32H7 controller platform with dual-core architecture, LVGL UI, RS485 communication, and ESP32-S3 connectivity co-processor • Ultra-low-power fault indicator for utility networks with multi-year battery life and LoRa communication • BLE thermal printer platform focused on wireless stability, motor control, print control, and production reliability Why clients work with me: • Strong debugging and root-cause analysis • Real production and manufacturing support experience • System-level architecture thinking • Clear communication and practical decisions • Reliable long-term collaboration Available for: • Firmware debugging and stabilization • Custom board bring-up • New feature development • RTOS-based firmware architecture • Wireless and industrial communication projects • Long-term embedded support Based in China (UTC+8), with flexible overlap for US / EU / AU teams. Typical response time: within 4 hours. Currently available for new debugging, bring-up, and embedded firmware support projects.

Senior Software Architect specializing in secure systems and IoT Sec solutions with 15+ years of experience. I architect and deliver end-to-end nfc solutions, from embedded firmware to cloud-based backend systems. 🎯 CORE EXPERTISE IOT Systems - NFC Solutions: Reader/Writer, HCE, Digital Wallets (Android/iOS) - Smart Cards: JavaCard, MIFARE, DESFire, NTAG,Global Platform,GP,JCOP,Secure Element - Security: PKI, FIDO, Secure Element,HSM, PCI-DSS Compliance - RFID Systems: Asset Tracking, Access Control - EMV Payment: L1/L2/L3 Kernel Development & Certification - Microcontrollers: ESP32, STM32 (WiFi/BLE, RTOS) - Firmware: Secure Bootloader, OTA Updates, Real-time Systems - Industrial Applications: POS Terminals, Vending Machines, Access Control - IoT Architecture: Sensor Integration, Remote Management Full-Stack Development - Backend: Node.js, REST APIs, Database Design (SQL/NoSQL) - Cloud Services: Firebase, AWS/Azure/GCP Deployment - Mobile: Android (NFC APIs), iOS (CoreNFC), React Native - Desktop: Qt, .NET, Cross-platform Applications - Languages: C/C++, JavaScript/TypeScript, Java, C# 💼 SIGNATURE PROJECTS ✅ ESP32 IoT Systems - Created NFC-enabled payment solution with cloud integration - Built secure firmware with OTA update capabilities - Integrated Firebase for real-time data synchronization ✅ Cross-Platform Digital Wallet - Developed mobile wallet supporting EMV contactless payments - Implemented HCE and Secure Element integration - Built Node.js backend with Firebase authentication ✅ Enterprise RFID Solutions - Designed asset tracking systems for industrial clients - Implemented access control with NFC/RFID readers - Deployed cloud-based management platform ✅ EMV Payment Terminal Solutions - Developed EMV L2 & L3 kernel for contact/contactless terminals - Achieved EMVCo certification for payment applications - Implemented secure key management and transaction processing 🔧 TECHNICAL STACK Hardware: ESP32, STM32, NFC Readers, RFID Systems Backend: Node.js, Express, Firebase, REST APIs Database: MongoDB, PostgreSQL, MySQL, Firestore Cloud: Firebase, AWS, Azure, Docker deployment Mobile: Android, iOS, React Native Desktop: Qt, .NET, Windows/Linux Security: PKI, FIDO, PCI-DSS, Secure Boot 📋 CERTIFICATIONS & STANDARDS EMVCo, PCI-DSS, PBOC, Global Platform, ISO 14443 I deliver production-ready solutions with clean code, comprehensive documentation, and ongoing support. Available for both fixed-price projects and long-term contracts.

I am a professional embedded software engineer with more than 10 years of experience. My current areas of expertise are IoT Applications & Embedded Systems Design, including embedded hardware/software. My Skills: - Know about MCU: Nordic, Silicon Labs, AVR, PIC,ESP32, etc. - Have experience in programming languages such as C/C++, - Solid knowledge of standard interfaces such as I2C, SPI, UART, and CAN. - Have experience using debugging tools such as Segger Jlink, CAN bus analyzer, Logic analyzer,RF analyzer. - IoT devices with wireless connectivity such as LTE, CAT-M1, NB-IoT, BLE, WIFI, NFC - Good experience in Battery Management Systems based on BQ products from TI. - Have experience using Alitium designer,Kicad - Know about medical Regulations and Directives such as EN 300 328,RoHS & REACH，EN 62368-1，EN 55032, EN 55035 etc. The development platform : - Keil .stm32cube, Micochip studio - On semiconductor IDE, Simplicity studio, - esp32-idf, Arduino - nrf connect sdk What I can do for you: (1 ) Electronic components selection,Schematic , PCBA design, output production files (2) Help you to review schematic , pcb files, and test hardware (3) quickly assist in making pcba samples, functional verification and abnormal problem analysis (4) Embedded software development from 0 to 1. (5) Help you to add new function or module to your embedded software system (6) Help you to review code ,test , fix bug in softeware (7) Based on the prototype of your needs, convert it into an actual embedded system design My advantage: （1） The processing and manufacturing efficiency in China is very high, and the cost of components is very low. If you want to do circuit modification and verification, I can use China's JLC and Taobao to quickly make PCBA. （2）I'm a full-stack developer capable of tackling both software and hardware challenges. This allows me to consider software design feasibility and convenience from a hardware design perspective, and vice versa.

👋 Hello, I am YanXia Xu. Embedded Systems Engineer with nearly 30 years of experience in industrial automation and embedded firmware development. Specialized in MCU firmware, RTOS-based systems, industrial communication protocols, and embedded Linux platforms. Extensive experience supporting Japanese enterprise projects and long-term industrial product maintenance. Strong background in debugging, hardware-software integration, and reliable embedded system design.