Abstract
<title>Abstract</title> <p>This paper presents a complete IoT gateway solution based on the ESP32 microcontroller and the SIM7600/A7670SA cellular module, developed to address the lack of native software libraries for these modules in the Arduino ecosystem. The proposed system implements a fully functional data acquisition, cloud communication, and device management platform using direct AT command manipulation over serial interface, eliminating the dependency on proprietary libraries. The architecture features a dual-core design where Core 0 handles all modem communication while Core 1 manages a built-in web server that provides a complete graphical configuration interface. The system supports automatic network mode fallback (5G/4G/3G/2G), GPS positioning with tower triangulation fallback, SMS-based alerts, and bidirectional data transmission with the TagoIO cloud platform. A buffered data sending mechanism aggregates multiple sensor readings into a single HTTP request, reducing network overhead and power consumption. Experimental results demonstrate that the 2G mode achieves the fastest connection establishment (~3.4 s) while 4G provides better throughput for data transmission. The complete firmware is open-source and available on GitHub, enabling easy deployment in rural and remote monitoring applications.</p>