Research On IO Device Based On PROFINET Communication Protocol

With the widespread use of incremental encoders as well as the rise of PROFINET real-time Ethernet in the field of industrial control, it is important for us to study encoder with PROFINET communication interface. In this paper, the encoder signal processing and PROFINET communication are combined. As a result, the IO device with PROFINET communication interface is designed, which can measure the motor speed, position and direction.This paper does research on the implementation methods for improving real-time performance of PROFINET communication, and gives the way to calculate data transfer time of RT and IRT. Compared to several speed measurement methods, the variable M/T method is chosen to measure the motor speed.According to the requirement of system function, the hardware design of PROFINET IO device is accomplished, including communication interface module centered on ERTEC200, signal processing module, power module and so on. At the same time, the circuit diagram of each module is explained.This paper introduces the general procedure for eCos transplant and the basic structure of the PROFINET IO stack. By using the Verilog HDL language, the design of encoder signal processing module is completed. This module can realize fourfold frequency multiplication, phase discrimination, position count, variable M/T method, A/D sampling and other functions.The hardware test platform of PROFINET IO device is built, and the test of IO device is done by SignalTap II, Wireshark and monitoring software. The result shows that the IO device can obtain the speed, position and direction information through the PROFINET communication protocol, and achieves the expected goal.