Design Of Kernel Driver For SLIC Telephone Control Chip In CPE

With the continuous improvement of users’ communication requirements,how to ensure the stability of the network and how to provide users with reliable,non-blocking communication circuits are the primary tasks of service providers.To achieve this,in addition to implementing corresponding safeguards on the network itself,the chip that controls the subscriber line interface circuit(SLIC)of the phone is also particularly important.SLIC circuits are widely used in switching equipment and access network equipment.In digital switching systems,the interface between a user’s telephone and a telephone exchange is implemented using SLIC circuits.The SLIC circuit is very important as a control interface for connecting analog telephone lines and PCM digital signals.In addition to data flow,telephone control is also an important function of the SLIC,like ringing,generating tone and caller ID.The DUSLIC XS series PEF31001 chip used in this project is a SLIC voice line terminal chip produced by Intel company.It can reduce the cost for the manufacturer when providing broadband voice calls.It has an integrated DC / DC mode,can support two voice lines with the same power converter,and can achieve excellent power consumption index,and calmly meet various specification requirements.This paper starts with the analysis of demand description,gives the overall architecture and software architecture of the system.According to the system requirements,the system is divided into PCM channel kernel subsystem and Control channel kernel subsystem.This paper focuses on the software development of embedded Linux kernel driver,which makes the system realize the adaptation of SLIC chip.By building ALSA audio framework and ASo C audio system,the corresponding DMA controller driver is designed,and the operation method of DSP equipment is defined,so that PCM data stream can be controlled and transmitted.Based on hwdep module,ioctl similar to character device is implemented,which can receive commands from voice application program.The input subsystem is constructed so that the kernel can report the events of the telephone to the user space for further processing,and finally the kernel driver adapts to the SLIC chip.When connecting the telephone,the chip will generate analog signal of telephone line according to the actual call scenario,which can drive FXS to generate ringing on the telephone,various prompt tones(press key,call waiting,busy tone,reminder,etc.)before and after the call,on/off hook signal detection,mutual conversion and transmission of analog signal and digital PCM signal during the call,as well as CID display(FSK and DTMF),and realize the basic call function.Finally,the separately compiled SLIC voice call module is loaded into the system kernel in the form of KO,and the voice functions are tested successively according to the test list obtained from the above analysis of requirements,all of which meet the requirements.