| Fieldbus is a new technology developed in the field of industrial automation in the context of digital development. Its fully distributed, highly decentralized control structure enables enterprises to reduce costs and improve efficiency. Profibus-PA is the typical application in the field of process automation of Profibus technology. It meets IEC1158-2transmission technology, ensure the intrinsically safe requirements and provides bus-power, which has been one of the most widely used fieldbus. There are many companies and institutes research on Profibus-PA technology, but the core protocol stack technology generally resolved through buying dedicated chips, only fieldbus interface technology was self-developed.This paper studies the physical layer, data link layer and user layer protocol model as well as the PA Profile of Profibus-PA technology. On this basis, a overall hardware architecture center on ARM7chip is determined. In which the latest SPC4-2chip which support Profibus-PA communication is adopted, and MAU unit is independent designed in communication part to meets the special requirements of IEC1158-2. The temperature transmitter section selects a24-bit high-precision AD sampling Controller AD7794, which ensure the multi-channel high-precision temperature measurement.After successful building of the hardware platform, the software design starts. Whose work can be divided into three main items:the realization of the the Profibus cycle and acyclic communication function, temperature transmitter software design as well as the realization of PA Profile. Through a combination of hardware and software, a PA temperature transmitter was successfully designed. In order to test the performance of the product, a test platform was built. The results prove that the product can communicate properly and the accuracy of temperature transmitter can reach0.2%in a variety of input sources and complicate environment. |
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