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This article delves into the principles and advantages of LoRa as a core Low Power Wide Area Network (LPWAN) technology. Starting with the Chirp Spread Spectrum (CSS) mechanism, it details the impact of key parameters like Spreading Factor (SF) and Bandwidth (BW) on performance. By comparing LoRa with solutions like NB-IoT and BLE, it highlights its unique value in long-range, low-power, and large-scale connectivity, showcasing its potential through real-world cases.

The concluding article of this series, focusing on exploring the advanced features of the DMR858M module. It covers low-power operation, DMR advanced calling (private/all call), SMS sending/receiving, emergency alarms, voice encryption, and the implementation of repeater mode. Mastering these functions will make your custom walkie-talkie project more complete and professional.

This article is a practical guide to developing ESP32 firmware for the DMR858M module. It proposes an object-oriented driver design method and demonstrates the core code implementation for packet construction and checksum calculation. It also emphasizes the importance of non-blocking asynchronous operations in embedded systems and provides a complete proof-of-concept program to help you get started with software development quickly.

This article deconstructs the binary serial control protocol of the DMR858M module in depth. It analyzes its data frame structure, checksum calculation method, and provides a complete command code reference table. Mastering this protocol is key to implementing module function control and parameter configuration, laying the foundation for subsequent firmware development.

This article details how to integrate the DMR858M module with the ESP32 hardware. It focuses on the key challenges of power supply design, especially how to handle high transient currents to avoid system reboots. Detailed interface logic instructions (UART, PTT, audio) and a proven pin mapping reference are provided to help developers quickly build a stable and reliable hardware prototype.