The Research Of Networked Embedded Railway Scheduling Monitoring System

The telephone voice monitoring is used in almost all of the scheduling industryon a wide range of applications, such as security, transportation, nuclear power, banks,railways and other industries, because of its backup and playback, real-time, easyaccess and other features. With the rapid development of electronic technology,network information technology, voice codec technology and integrated chiptechnology, Voice call monitoring develop from the initial tape monitoring equipment totoday’s large-capacity Internet-based embedded monitoring equipment, whether itsfunction or storage capacity, voice monitoring can’t compare with the past. Especiallywith the appearance of embedded real-time operating system, system-on-chip andnetwork technology, voice monitoring equipment develop toward the direction ofminiaturization and network.It also experienced the process based on the PC, FLASH chip and mobile harddisk and other media in the course of the development of monitoring equipment, butunable to meet the needs of most users because of the high cost, big bulk, limitedstorage capacity and other defects. Based on the above requirements, we design anetworked embedded audio monitoring system. Compare to the normal voicemonitoring system, the system has higher reliability, greater interface flexibility,higher security and better electromagnetic compatibility.The components of networked embedded audio monitoring system include voiceacquisition circuit, the AD control circuit, the memory circuit,3.5-inch LCD resistivescreen interface circuit, USB2.0interface controller, SD card interface, ring detectionand telephone decoding circuit, the front-end conditioning circuit of the voiceinformation, Ethernet interface circuit and S3C2440core circuit. Microprocessor S3C2440-based embedded system platform, the entire system architecture has taken amodular design, which reduces the difficulty of development, improves systemreliability and reduces development costs. Each module can independently debuggingand run. The system includes master module, AD configuration and audio capturemodule, audio decoding player module, external memory interface module andnetwork communication module, this article analyse and design the five-part andcompleted bare machine testing procedures.Master module is the heart which completes system control, datacommunications and voice data processing and other functions in the whole system.Master module uses six core board design. Core chip S3C2440integrated SPI businterface and I2S bus interface, you can directly communicate with the FPGA and thesound card chip with the I2S interface. Data acquisition board transmit audio datacollected through the SPI bus to the main control module, which encodes the datareceived and gives encoded data to the sound card to play through the I2S interface, atthe same time saves it in peripheral as a post-query backup.The AD and audio acquisition module consist of ADI voice capture chip AD1974and the Altera Cyclone IV series EP4CE6E22C8. In this system, the AD1974capturesfour audio at the same time(The chip also can be expanded into simultaneousacquisition of16-channel audio if necessary), and transmits the collected data to theFPGA to deal with through the SPI bus. AD acquisition data of four audio contains64bits, the first, second, third, four-channel data are located pin ASDATA1andASDATA2.The format of data on the ASDATA1pin is a one-channel32-bit andtwo-channel32bit, the format of data on the ASDATA2pin is three-channel32-bitand four-channel32bit. AD1974configuration is16bit quantization, a delayed clockreceive data, the most significant bit of each32bit data are invalid, valid data is the16-bit data from the second high bit. Based on the calculation of the effective data,FPGA takes out64bit valid data of the four channels and integrated together into aframe of data according to channel sequence. In order to facilitate the transfer of dataof the operating system, the format of16-bit data each channel are lower eight bits inthe front and the higher eight bits in the latter. Considering synchronization problemof the data transmission between the different systems, we replace the lowest two bitsfor each channel with the channel number (channel number of the four channels,respectively00,01,10,11), and then transmitted to the main control module via theSPI bus. The FPGA also responsible for controlling the configuration, storage, processing of the voice capture chip and transmission of voice data. The way whichFPGA and CPU jointly controlled voice capture chip not only improves the real-timeperformance and efficiency of the system, but also reduces the difficulty of design.The core chip of audio decode and play module is Philips’s UDA1341, which is aprofessional-grade sound card chip and integrates programmable gain control moduleand the filter module on the chip, can record the pure sound in a relatively harshenvironment, good filtering effect of background noise, the results would be better toplay audio files. In this system, the main function of the module is communicationwith the main control module through the I2S bus interface, receiving coding voicemonitoring information of master module and playing information received real-time.External memory interface module includes a USB interface and SD cardinterface, USB ports can expand hard disk easily, thus making storage capacity greatlyincreased. The USB interface can storage data, transmit data, process data and also beconnected keyboard, wireless LAN and other peripherals. USB2.0OTG (On-The-Go)technology is used on the interface, it complete the transmission of data betweendevices without Host, so that the system get rid of the restrictions of the master-slavearchitecture to achieve the end-to-end data transfer mode, which allows the USB datatransfer data between the devices without HOST, thus making the problem of highcosts and big bulk based on PC-monitoring equipment solved. In addition, SD cardand USB interface support hot-swappable, it has practical significance for on-sitevoice monitoring.Network communication module design Ethernet controller, the core chipDM9000adaptive speed10M/100M and is connected to the LAN and the Internetthrough controller, upload recorded voice messages to the network terminal, realizethe information interaction and sharing between multiple sites. The introduction ofnetwork technology is a major innovation of the system, network-based voicemonitoring system is a new trend in recent years in the monitoring industry, andgradually replaces traditional monitoring equipment because of its unique advantagesof resource sharing.