Development Of Industrial Digital Command Telephone System Based On CAN Bus

In the scheduling environment of industrial field, transportation, power system andso on, there always produce voice command scheduling, contact, or monitoring andother needs. However most voice communication system are based on the traditionalcircuit-switched technology, routing technology or Public Switched Telephone Network(PSTN). Traditional voice communication system has many defects, such as when nodeincreases, the address will be very large, which provides the designer with a heavyworkload. It brought a heavy burden to the maintenance as there are a wide variety ofcomponents and the number of cables. It waste bandwidth because of low or no voicecompression. It can not meet a variety of requirements because of its singlecommunication mode. In actual R&D and use, it often causes complex development insystem, manufacturing and maintenance costly and other drawbacks.As one of the multi-master serial field bus, CAN bus can support for distributedcontrol effectivly. CAN bus has many features such as simple communication hardwareinterface, flexible choice of communication medium, low prices ans so on. Thus CANbus was favored by the interconnection of field devices and was widely used in theautomotive automation, building automation, industrial control and other fields. CANbus mainly works in data link layer and physical layer of OSI model, it is an all-digital,two-way and multi-master field bus. CAN bus has many advantages such as strongerror-correction capability, long distance of transmission, fast transmission speed, stronganti-interference ability and so on. Therefore, it has an enormous practical significanceto achieve a voice communication system constituted by the CAN bus. Currently, theapplied research in voice communication system based on CAN bus is in the initialstage.On these bases, this article discusses the developed of digital commands telephonesystem based on CAN bus，which was used in industrial command scene.The paper described CAN bus technology and voice codecs principle in detailfirstly. Then use the theory of queuing theory to modeling and analysis the datatransmission on CAN bus. Analysis results is used to guide the parameters settings ofthe system at last. In hardware system, industrial-grade ARM9chip AT91SAM9260isused as the main system controller. AT91SAM9260is equipped with voice codecmodule and voice compression module to complete voice digitizing. By controlling the CAN interface module, AT91SAM9260can make the system connected to the CAN busnetwork. Then with auxiliary button module, display module, storage module, RTCmodule etc, a hardware environment which core as ARM9of instructions telephonywith multifunction was build. The system software was based on μC/OS-Ⅱ. Thedesign of the system application software followed by the steps of systemcommunication protocol design, state machine design and task division. At the first halfof the section the paper describes the technical principles of the system and at thesecond half the paper elaborates hardware and software design and system test. The testresults show that the system is stable and reliable, it reached design expectations.