The Design Of Embedded VoIP System Based On DsPIC33F

IP telephony is a voice communication tool which uses the Internet or otherIP-based networks as transmission medium. People pay more and more attention to IPtelephony with the development and popularization of the Internet. Compared withthe traditional phone, it shows us obvious advantages: low call charges and lowconstruction cost. Recently, there are a great many software products about IPtelephony which have been widely used in the market, but they also have adisadvantage which can not be neglected: poor removability. In order to solve theseproblems, we propose the design of embedded IP telephony aiming at workingindependently without the support of computer.Firstly, The classification of IP telephony were introduced in this paper. Secondly,we studied key technologies of IP telephony, which included Speech decodingtechnology and network communication protocol. Thirdly, we designed the hardwarecircuits,we chose the high-performance16-bit digital signal controllerdsPIC33FJ256GP710A as the core controller, selected WM8510as voice codec chip,used ENC424J600as the network controller. At last, we designed the software: Callprocessing module, A/D and D/A module, data packing and unpacking, the voicecodec module, network transmission module and serial transmission module. Thesemodules were achieved.In the design process of the IP telephony, the speech codec algorithm based onG.726A protocol and Speex speech codec algorithm were realized on the developmentplatform which used Microchip Explorer16development board. We chose Speex asthe codec algorithm of the IP telephony through comparing the performance andcomplexity of the two algorithms. We simplified the Protocol hierarchy of VoIP andachieved the network transmission based on TCP and UDP using Socket.