Design Of The Discrete I/O Device Based On Fieldbus

Along with information technology's development, the intellectualization, theinformationization, and the network become the modern industry control,s hot spots. Sincethe 1980s, the opening industrial control fieldbus has developed rapidly, and has changed thestatus of technology. Gradually, a kind of product, long-distance IO has developed maturelywhich is based on the network connections dispersion control and the embedded equipment'scontrol technology , may disperse the disposition in the field, connects local the input/outputsignals, realizes the request disposition.In the industrial control area, the fieldbus technology spreads control functions to thefield. MODBUS is one of the fieldbus standards, it conforms to the IEC physical layerstandard, provides with dual-media redundancy and time-critical transmission mechanism..Real-time industry field discrete data's gathering presents developers with a wide rangeof requirements including increased processing performance, low power consumption, highI/O bandwidth for data acquisition, scalable storage capability, reliability, long-life supportand standards-based connectivity. The wide range of ARM processors, whose characters arelower price, lower power consumption, easier development and higher processingperformance, helps developers deliver the highest performance for the gathering system.S3C2440 is one kind of technical grade ARM microprocessor, because of its high ratio ofperformance to price, its high dependability and so on, therefore selects it to do for the systemdevelopment hardware platform.Linux operating system is widely used in ARM application in virtue of its simply andhigh efficient kernel, abundant network performance and sustainment to many processors,enabled it to obtain the widespread application in the embedded industrial control area, butthe real-time processing industry field discrete data is one of industrial control domain mainapplications.In this paper,"Design of the discrete I/O device based on fieldbus"implements an intact and general embedded system development platform. It briefly introduces the I/O devicebased on the MODBUS fieldbus, this device has connected the MODBUS fieldbus and thetraditional discrete control device. First briefly introduces the system overall concept design,second, divides into the system design the hardware design and the software design two majorparts.The system hardware first carries on the simple introduction to the ARM processor andthe S3C2440 microprocessor, importantly elaborated the S3C2440 processor and the memory(Nand and SDRAM) connection and so on RS485, GPIO designs, analysis to the discerteinput/output circuit in depth, may simultaneously carries on 16 group discrete the output andgathering, and has made the related debugging to the hardware.The system software divides into the superior machine and the lower position machinetwo parts: The superior machine takes Windows XP as the developing platform, uses theVC++ software designing communication surface, MSComm controls to carry on theMODBUS serial port programming, it has the simplicity of operating and strong flexibility.The lower position machine takes embedded Linux as the core platform, first constructsembedded Linux, mainly includes bootloader, kernel translation and transplant as well asfilesystem's construction. Then to the MODBUS agreement's transplant and the characterdevice driver (serial port, GPIO) has made the thorough analysis, especially has realized withthe C language based on RS485 the communication MODBUS serial port programming, hasgiven the software flow chart and the core code, and has carried on the debugging to thesoftware.