Design Of Digital Visual Intercom System

With the raising of national economy and the development of computer technology, people put forward higher requirements for the safety of the home environment. Video intercom systems have become an essential infrastructure of residential area. However, Most of the current building intercom systems are analog systems, using the analog audio and video signal transmission. The analog system has many limitations, such as wiring complexity, high cost, limited transmission distance, anti-interference ability, poor stability, poor compatibility. The digital video intercom system solves these problems.A design of digital video intercom system with multimedia processor SoC i.MX27is presented in this dissertation. i.MX27is a multimedia processor SoC based on the ARM926core,it integrates H.264/MPEG4full-duplex hardware codec video processing unit.First, the system architecture and overall design are proposed in this dissertation according to current trends of video intercom system and the technology of audio and video network transmission.Then, the schematic design is completed based on the working method and implementation of each functional module, cluding H.264video codec, audio codec, DDR memory, RTC real time clock, RS-232/485communication, Ethernet communication.Considering the signal reflections, crosstalk and power integrity factors, the PCB design is completed based on the high-speed signal integrity circuit theory and high-speed PCB design experience.Also, based on Linux system, the Bootloader and device driver for each module are designd in this dissertation according to the application requirements.Finally, the system is modular tesed and joint debugged.After debugging, the system realizes the functions of digital video intercom system, the performance has achieved the desired objectives, and the system is stable and video calls perform well.