Design And Realization Of An Embedded IP Phone Terminal

Based on the analysis of current situation and the development trend of IP phone, this paper has put forward the solution of a kind of new-type embedded IP phone terminal and has finished designing the IP phone codec which is the key part of IP phone terminal.The hardware of the IP phone codec to be designed is based on the fixed point digital signal processor (TI'S TMS320VC5410) while the compression and decompression core in the software of DSP is based on the ITU-T vG.729A .IP phone codec carryout the task of collecting /playing-back .coding /decoding of speech signal and communication with embedded CPU.etc.The existing fixed-point implementation of G.729A is generally written on all-purpose computer, and is no considered real-time quality problems . So the algorithm is needed to be optimized . when testing the G.729A ANSI C source codes offered by ITU-T, we found that some basic operations are called several thousand times and consist of more than 90% of the operation quantity of the whole algorithm.After optimizing these basic operations with the method of combining intrinsic with macro language,the complexity of calculation of G.729A encoders is reduced from 530 MIPSs to 94 MIPSs. This is a key for the optimizing of the whole algorithm . Then,the digital signal processing functions in G.729A are optimized by DSPLIB.According to the structure characteristic of DSP,some sentences of circulation and shifting are rewritten.Finally,the complexity of calculation of the whole algorithm is reduced to 30 MIPSs,which satisfies the real-time request very well.This thesis has put forward IP phone terminal solution of DSP+ embedded CPU ". On the basis of this scheme, this text introuduces the IP telephone systematic framework and the selection of chips for the codec. The circuit design ,focuses on the following hardware modules: power structure environments, A/D,D/A inverter, DSP and embedded CPU's communication interface,DSP modules,and so on. The problems and the corresponds solutions which found in the design and debug are discussed,too. At last, the software design is presented in detail,including system booting,initialization of DSP registers,drivers for AD converter and system software.