Design And Implementation Of The DeviceNET General Purpose I/O Node

With the rapid development of fieldbus, DeviceNET is access to wide attention and development. DeviceNET is a kind of fieldbus standard set by the Rockwell automation company. And it is one of the first batch of national standard fieldbus. Therefore it is necessary to develop DeviceNET fieldbus products with our own independent intellectual property rights. Developing DeviceNET products generally utilizes special imported protocol chip since its complexity. However, it will cause a higher cost and the lack of independent intellectual property rights. In order to reduce the cost, improve the competitiveness and enhance economic benefit, it is significant to realize a DeviceNET general purpose I/O node.The thesis widely investigates the development of fieldbus and DeviceNET, and then determines requirement of subject and the scheme of design. The system design scheme was established and the software and hardware of DeviceNet general purpose I/O node was developed based on contrasting to many design scheme of DeviceNET slave station.The DeviceNET protocol stack software was developed using Code Composer Studio 5.5.0 software integrated development environment and TMS320F2812 development board. The design of protocol stack software achieved DeviceNET slave station code of predefined master/slave connection set which could support UCMM function based on the event-driven state mode algorithm. Meanwhile the design completed the transceivers of CAN data and serial data in the DSP embedded processor. And it visualized the result with the serial debugging assistant and the CAN Pro debug software supporting DeviceNET protocols.In order to facilitate the further research, this thesis designed hardware schematic, draw the PCB on Altium Designer hardware development platform, and makesDeviceNET general purpose I/O node special purpose hardware circuit board. TMS320F2812 embedded processor was adopted in hardware design, SN65HVD253 CAN transceiver and serial transceiver MAX-3232 which were both from TI Company were respectively used in the DeviceNET data transmission and I/O data transmission, and expanding the RAM and other hardware circuit.Considering verify the accuracy and stability of the system design, according to the master-slave station communication process described by DeviceNET protocol specification, DeviceNET test platform was designed to build up and communication protocol conformance test was completed on DeviceNET purpose I/O nodes. Through the test, it was verified that general purpose I/O nodes conform to the design requirements of DeviceNET slave station. In addition, on account of its real-time and stability, the communication with the master station was also realized. This thesis had certain reference value for further research and development of DeviceNET fieldbus protocol specification.