Design and Innovation of Asynchronous Serial Communication Interface Conversion System of Field Bus

Since the traditional asynchronous serial communication interface conversion system has a series of problems in data reliability, CPU utilization and so on, this paper, starting from the design idea of fieldbus, uses CAN, PROFIBUS-DP, power conversion module, core control module and other software programs to study the conversion process, so as to innovate the conversion system and realize the reliability of data, which greatly improves the utilization rate of CPU.


Introduction
With the development of science and technology, the communication security between computer and peripheral equipment is particularly important. Serial communication has been widely used in measuring, automatic control and intelligent equipment because of its few transmission lines, simple design, low cost and convenient control. Although serial communication technology has gone through a period of development and is relatively mature, because of the increasing demand for data transmission, some engineering and equipment have put forward more stringent requirements for serial communication. Therefore, it is very important to innovate the method of serial communication and improve the reliability, stability and timeliness of data transmission.

Value analysis of fieldbus
Because fieldbus can realize serial, multi-node word number and two-way communication, it brings diversified experience to users' network communication, so it soon becomes a popular new technology in the market. However, in the process of practical technology application, fieldbus always exposes a variety of problems, such as high material cost, limited scope of application, immature bus standards and so on [1]. If these problems are not dealt with in a timely and effective manner, they will seriously hinder the development of the communication industry.
Asynchronous serial communication is one of the main working objects, it is of great significance to improve the efficiency and accuracy of fieldbus. However, in reality, most of the research on interface conversion system is still in the single field bus conversion, Not only single function, but also lack of flexibility in operation, can not meet the higher requirements of field industry. To solve this problem, a RS-485 interface technology is proposed, which uses differential square transportation mode, half-duplex communication bus, and finally realizes 1200 M transmission distance. It is widely used in the field of point-to-multipoint communication. The engineering circuit is shown in figure 1: RS-485 interface technology has the above advantages, but it is difficult to guarantee the reliability of data due to the influence of hardware and software environment, industrial conditions, software design and so on. for this reason, this paper proposes an innovative interface conversion system from the perspective of CAN and PROFIBUS-DP bus design. to achieve the purpose of network resource sharing and data security.

Hardware design
The system is initially designed as the following six modules: CAN bus interface, PROFIBUS-DP bus interface, core control, interface conversion, power conversion and bus selection switch. The structure distribution is shown in figure 2: Figure 2. Structure distribution The system will set up 3 endpoints ,2 switches, one of which will contact the system chipset, as shown in Figure 3:

Core Control
Module.The core control module of this design is C8051F040 single chip microcomputer, which has the advantages of strong anti-interference, low digestion power and strong processing ability. By C8051F040 the setting of single chip microcomputer, the conversion system can effectively increase the hardware integration and reduce the development cost at the same time. As the kernel of the single chip microcomputer is CIP-51, instruction set structure is 8051, which can be effectively compatible with each other and further improve the working frequency of the system [2]. The internal overall structure diagram is shown in figure 4: Figure4. The internal overall structure diagram

communication interface.
A bus driver, a protocol controller and an optocoupler isolation circuit are included PROFIBUS-DP, the bus communication interface. In order to ensure the overall function of communication, the module designs a network device on the bus arrangement to realize data transmission and conversion with other devices. The communication interface module has a total of 7 layers, in which the lowest layer and the microprocessor complete the data processing of the 2-7 layer together. Because the data of the second layer is in the chip of the core control module, it is difficult to process. Other levels of data are relatively easy to process. Notably, its data exchange exists independently at all levels. Because the microprocessor in the communication interface plays an important role in the whole module, it is necessary to design a specific solid state program to adjust the microprocessor in time. Generally speaking, the communication module can be compatible with 80 C32, 80C166, 80X86, 80C167 and other chips, has strong compatibility [3], and can effectively realize the application and communication cycle. Besides, because of the differential driver and RS485 transmission technology, the module also has the advantages of strong anti-interference, high driving and low consumption.

Software design
The system will be based on the keilμVision2 development environment and CI5 program, using the 805 X compiler and 803 compiler to develop and design the software, so that the microcontroller and MCU better operation, to ensure that each module cooperate with each other, Its software structure diagram is shown in figure 5:

Conclusion
On the basis of CAN and PROFIBUS-DP bus technology, this paper creatively puts forward the design of asynchronous serial communication interface conversion system based on field bus, which has positive practical significance for the reliability and industrial efficiency of communication data.

Terminology
On the basis of CAN and PROFIBUS-DP bus technology, this paper creatively puts forward the design of asynchronous serial communication interface conversion system based on field bus, which has positive practical significance for the reliability and industrial efficiency of communication data.