Digital Audio Transmission Terminal Based On ARM7

This thesis studys on the design of application . On many occasions like in the classroom and some important meetings ,we need to spread the voice from one to one or one to many and record the realtime information. The portable digital audio transmission and storage terminal can achieve and deal with realtime audio information, transpor through the wireless transmission modules, achieve large data storage ,and also can broadcast the audio.Digital audio technology is the further development of audio technologoly. Digital audio technology is a means to pursue the ultimate goal of high-fidelity analog audio signals, high-speed transmission and long time storge.As a portable product, it's core system must be compact and Superior performance. The advantages of the embedded microprocessor,whice has a small size, fast response, rich resource, high stability, make it have many applications in the information and civil areas. Especially in the portable media technology, it will play an increasingly important role.It provides a solid foundation for the realization of paper.The present study uses an embedded system as the core,and codes the digital voice information.Then the system transport realtime information by wireless transmission equipment,and can achieve large capacity information storage.Firstly,Paper studies the characteristics and resources of embedded microprocessor of LPC2138. It demonstrates its feasibility as a core processor. And designs the smallest system and simple control of peripheral devices based on it.Then it studys of the digital audio technology which is the object of the thesis. After understanding its main characteristics and treatment methods, we determine to use adaptive differential pulse code modulation(ADPCM) to deal with the digital audio signal. It uses the correlation between voice signal sample. And as the voice signal has the characteristic of non-stationary, it uses adaptive prediction and adaptive quantization. It makes the audio get great quality at 32Kb rate and can achieve high fidelity audio .After Learning the basic concepts of system architecture, it designs the program of the system. The system uses the LPC2138 as the core processor, mainly to achieve the audio signal A / D and D / A conversion, ADPCM codec, and system peripherals control. Peripheral devices include audio capture circuit, audio broadcast circuit, the wireless transmission module, 3.5-inch LCD display, SD memory and USB host memory interface. The wireless transmission using NRF2401. It works in the global open band of 2.4GHz. It has 125 channels, and can transport from one to many. It uses efficient GFSK modulation, so that the wireless transmission has the better anti-interference,and security. Theoretically,it can reach a maximum communication rate of 1Mbps. It meets the needs of the system and get low-power features. In the data storage section, it uses the SD memory technologies.And also for better compatibility with existing data storage devices, it expand the USB host storage mode. It uses CH375 master / slave control conversion chips.the design of its basic operation achieves high-capacity data storage.It designs the printed circuit board of the system based on The whole circuit ,and debug the soft system. It uses realView MDK as the development platform. It designs the soft programs of audio processing, wireless transmission, data storage inμVision3.At last, it designs the soft program of the system and debug it to get the ultimate realization of system functions.Finally,it tests and analysis the performance of the system , determines that the optimum operating environment is 20 m transmission distance,with 16KHz sampling frequency and 16bit median sampling precision.system uses the ADPCM encoding method. Thesis not only studys the theory of the digital audio transmission terminal based on ARM7 ,but also studys the concrete practice of the system studied, produces a printed circuit board of the system.And it Realizes the basic functions of the system.The system of digital audio transmission terminal based on ARM7 looks small but has enough functions. It has practical applications. It can simply be used in the classroom and meetings which need to record the voice. It can transport the realtime and high fidelity audio information,also realizes large data storage.All of those make it have good market prospects.