The Digitized Speech Classroom Based On H.323 Protocol And μC/OS-Ⅱ Platform

It is enormous commercial promise to develop the multimedia application in IP network.H.323 suggestion is a multimedia meeting system which is based on the packet exchange network (PBN) and made by ITU-T.H.323 meeting system does not assume that its network foundation of working can offer the service quality (QoS) to guarantee.This subject takes "digitized pronunciation classroom" as an example,Have analysed conscientiously and put forward a realization scheme.This scheme is based on H.323 agreement,there are three main tasks.First,Transplantation of embedded real-time operating system μC/OS-II.Second,Expand the system structure of RTOS on the basis of μC/0S-II.Finally,H.323 IP intelligent terminal based on μC/OS-II+LWIP is realized through analyzing conscientiously it.Student terminal adopts TI dual-core processor TMS320VC5471 which integrates a 16-bit fixed point DSP (100MIPS) subsystem and 32-bit RISC micro-controller subsystem. Media access control (MAC) on Ethernet linker layer,μC/OS-II operation system and LWIP protocol are embedded in this chip, which compose the IP intelligent terminal.In the research,The system Boot procedure is designed after analyzing all the characteristics of the TMS320VC5471 EVM.OS_CPU.H, OS_CPU_A.C,OS_CPU_A.ASM of these three procedures areprogrammed according to the EVM after studying all the C cores in the μC/OS-II.Design and debug of the assembly language about the target processor are implemented.By CCS development platform mixing compile and link technique,μC/OS-II is integrate with initialization source codes of system into a full apply.μC/OS-II is only a real-time multitask kernel.Having transplanted uC/OS-II to the processor platform,it is only first step from actual application.We must carry on essential expansion to μC/OS-II and set up a simple and practical real-time operating system(RTOS).Because this subject must realize a H.323 terminal on the basis of μC/OS-II, so we must expand TCP/IP protocol on the foundation of μC/OS-II kernel.I have selected LWIP(light weight ip)that is an opening source code and minitype TCP/IP protocol and used in the embedded system by Adam Dunkels,etc in Swedish Institute of Computer Science.To realize μC/OS-II integrate with LWIP seamlessly, it is necessary to make corresponding modification to μ C/OS-II and LWIP.For example:the support in thread,the modification of signal flag and news queue communication mechanism in μC/OS-II,timer,etc.Then write a driver of network and series to ARM7TDMI.Finally,realized transplantation of μC/OS-II +LWIP on ARM7TDMI.H.323 has four components.and student terminal (IP intelligent terminal based on uC/OS-II +LWIP) is the realization of the terminal component of H.323 on the basis of uC/OS-II +LWIP,which can be connected with teacher computer,and Switch though twisted-pair.It makes the acoustics of the system more perfect because real-time implementation of speech coder algorithmin the DSP.This component can be used as occasions,such as IP telephone terminal, long-range controller based on IP ,etc.