The Design And Realization Of Paging Telephone Based On CAN Bus

CAN (Controller Area Network) or Controller Area Network is a distributed control or real-time control of the serial field bus communication network. As a technologically advanced, high reliability, function perfect, cost-effective remote network communication control mode, it has been widely applied to various automatic control systems.In industrial communication, data transmission required to meet timeliness and the real-time system response. Emphasis on industrial networks in industrial environments the integrity of data transmission, communication network works in the field of poor industrial production, it is necessary to address the issue of environmental adaptation. The call the industrial scene should be ensured that calls is real-time, the delay may result in the failure of command. Secondly, it must ensure the fault-tolerance of voice and data communication on the lines. In the industrial scene, often as a result of various kinds of interference, so that information received by the receiver error. The voice data errors can cause ambiguities or discrepancy. Moreover, in some cases, the confidentiality of data is also very important. Traditional telephone communications system includes terminal equipment, transmission equipment, switching equipment. To ensure that any users of the telephone network can communication with all other users, it is necessary to rely on the telephone switchboard. The use of telephone exchanges, each phone will need a pair of transmission lines to connect to the switches. If use traditional phone calls in the industrial field, because of the need for traditional phone switches and routers, so there will be a lot of complex line, and the cost of routing greatly increasing. However the walkie-talkie has a lower anti-interference performance, it is poor in confidentiality and difficult to meet the immunity requirements.This paper designs an industrial-site voice communication system base CAN bus. CAN has error frame automatic re-made features, high reliability and signal transmission with short-frame structure, low probability of interference, excellent error detection performance, so the Real-time and accuracy of voice can be guaranteed. In addition, CAN bus communication medium may be twisted pair, no special requirements, flexibility to expand the node, routing and installation are very simple, is also easy to maintain, the cost greatly reduced. The most important thing is, CAN encode the data block instead of traditional stations address encoding. Therefore it can communicate without telephone switchboard and the entire system only need to connect to two lines and get rid of the traditional large bundles of wiring.The system hardware has a platform on ARM7, with voice codec modules, voice compression modules, CAN communications modules, I2C keyboard modules, etc. Use of S3C44B0 extensive peripherals, built a hardware environment that core as ARM, from the voice compression and decompression of voice, to the data transmission and reception on CAN bus. This paper also introduced the whole system's software processes and software implement method of each function module. Test results show that the system is expected to complete all of the features, and works stably and reliably.