Smart Landline Terminal Design And Realization Of Digital Signal Codec

The smart phones can serve traffic, stocks, news and weather information subscription, caller ID and so on, and all the applications are based on digital signal. As we known, before sending or receipting digital signal through traditional telephone network, modulation and demodulation are required. Currently, most modulation and demodulation of communication data for telephone are dependent on specialized hardware circuit, while the control system with MCU core takes the software method, which could avoid additional hardware cost.In this thesis, SPT6608A microcontroller is employed as the control core, setting up corresponding reliable hardware environment. Take the view from software, we describes FSK and DTMF signal coding and decoding methods. Firstly a brief introduction FSK and DTMF signal characteristics and introduction of Sunplus SCM. Secondly discuss three FSK signal decoding methods, zero detection, filters, minimum estimated error, and discuss advantages and disadvantages of these three methods in the actual hardware environment. Thirdly introduce the realization process of minimum estimated error in detail. Fourthly introduce two DTMF signal decoding methods, one is fast Fourier and another one is Goertzel algorithm and analyze the calculation of these two methods. Discuss how to choose decoding method according to hardware restrictions. Fifthly introduce the realization of the software modulator and discuss how to make use of DA converters generate FSK, DTMF signal. Describes how to create a sine value table and improve the performance of modulator. Finally, the system performance test records and a brief analysis of the system performance are given.