Design of Digital Voice Conversational Terminal of Coal Mine Based on LWIP

Based on analysis of function limitation of underground speak telephone system, a novel scheme of digital voice conversational terminal of coal mine with network interface based on open-source LWIP protocol stack was proposed, the terminal's application function, hardware composition and software model were introduced, the LWIP protocol stack and its transplanting to FreeRTOS embedded operating system were described, and design points of LWIP in applications layer of the terminal were analyzed. The terminal has functions of digital broadcasting and talkback, uses standard RTP protocol, and supports voice interaction with 8 kHz and 16 kHz sampling frequencies and on-line streaming broadcasting of MP3 with up to 44.1 kHz sampling frequency. Feasibility and effectiveness of the scheme were verified by experiment results.