Research And Development Of Embedded PLC Module For Application Layer

In recent years,with the development of "made in China 2025",the manufacturing industry is not only simple to produce and process,but also need to provide high value-added services,as well as the personalized needs of users.As one of the most important equipment of industrial control,PLC will have an unlimited market in the future.In traditional PLC,simple ladder diagram,logic diagram or statem ent table are used in programming.It is easy to use without computer knowledge,and the system software development cycle is short and can be modified online.However,due to the inflexible collocation of IO points in traditional PLC,the price of IO points is proportional to IO points,which makes the cost of user development increase.With the development of science and technology,The types of measurement and control sensors and their communication protocols have changed greatly.The traditional PLC can not be compatible with this kind of communication interface,which is,for example,the sensor peripherals based on I2 C or SPI.In summary,aiming at the deficiency of traditional PLC,this paper puts forward the PLC module for application layer embedding,or PLC module or embedded PLC module,which means to embed traditional PLC into various industrial control boards in the form of module.Make it easier for developers to use the application layer.First,this paper takes Mitsubishi FX2 N type PLC as the res earch object,through analyzing its software meta-resources,instruction format,serial communication format,deeply understand the operation principle of PLC.Second,the hardware circuit of PLC module system is constructed with STM32,and be analyzed fro m 64 input and output channels,232 serial port communication circuit,power loss circuit and I2 C bus module.Third,the software system of PLC module is designed as the interrupt system,serial communication module,instruction interpretation module and I2 C bus communication module.Instruction interpretation module is the core of software system,without which PLC program can not be interpreted.There are two bright spots in the PLC module designed in this paper,the modularization of traditional PLC and used I2 C bus communication.The modular PLC can match the type and quantity of IO arbitrarily;and because the module itself has only business card size,it can be easily embedded in the main board circuit of industrial control.The I2 C bus communication is introduced into the PLC module to customize the access protocol compatible with the PLC language,so that the PLC can access more I2 C sensor peripherals.After a series of development processes,such as drawing hardware circuit diagram,software development,software debugging and so on,the prototype of PLC module is developed.This paper tests the operation effect of PLC module with two experimental cases,and verifies the feasibility and convenience of PLC modularization.However,due to the limited ability of myself,there are some problems and shortcomings in PLC module.In order to further improve the product,this paper puts forward the future improvement of PLC module.