The Research And Design On Component-Based Embedded PLC Hardware Circuit Design Platform

With the development of computer and microelectronics technology, the combining of PLC technology and embedded system become a new direction of the current PLC development, which is widely applied at various occasions. Although different embedded PLC products vary in terms of forms and function, they share the same overall structure. Basically, the embedded PLC is composed of the central processing unit (CPU), memory, I/O(input /output) system, communication interface, internal power module and other optional components. Many I/O modules with the same structure in a PLC would have the same communication and power module in different PLC. In other words, there will be many repetitive hardware designs of PLC. In addition, in the traditional design process, there will be many errors caused by human mistakes in traditional design process. For example, the network label errors caused by complex connection relationship, or duplicating component names caused by negligence of the component rename when a large number of copying components are copied from the same circuit. It will cost a lot of time for the designer to position the components according to the principle of the nearest.In order to reuse the hardware circuit module and improve the correctness of circuit design, we propose a circuit design platform which is based on design components. Firstly, the basic hardware circuit modules of embedded PLC are studied, we found that these modules have three common characters: high repeatability, generability, and independence. These features are in accord with the essential characteristics of the software components, which shows the feasibility to encapsulate these modules into components for the schematic design. Then, a conceptual model of hardware circuit component (HWCC) which supports hardware circuit is proposed on the basis of the research of the software component, component library of the corresponding and component assembling program. The current circuit design tools'network files, footprint library files, and circuit board files are used as interfaces of the secondary development method. And the external development method is used for developing the platform for the embedded PLC circuit design which is based on components. This platform is composed of footprint library, manage system of component library, circuits schematic designer, and parser. The footprint library is responsible for the footprint library files'import and storage. The manage system of component library is responsible for components'making, storage, dynamic modification and extraction. The circuits schematic designer use a graphical user interface for the component based designing of circuit schematic. The parser is in charge of the analysis of the result of the circuit schematic design, and generating corresponding circuit board file.The circuit development experiments show that this proposed platform can reduce the complexity of the circuit design, improve the correctness of circuit design and shorten the development time of circuit design.