Interface Conversion Design Based on FPGA-Soft-Macro for EnDat2.2 and RS232/RS485

The EnDat2.2 interface protocol developed by HEIDENHAIN company lately with its high-speed, bi-directional and pure digital features can meet the requirement of rapid responses, dramatically cut down the overall system's cost and greatly reduce the space requirements of the system's installation. Therefore, it is widely used in Numerical control system like CNC system and photoelectric encoder. China's first Micro-area X-ray Fluorescence Analyzer used a HEIDENHAIN encoder with this protocol to improve the three micro-platform positioning accuracy. However, considering the complexity of the connection interface to host computer and the high cost of dedicated interface card, the application adopted a new way to fulfill the serial data's transmission tasks rather than dedicated receiver IC. Based on soft-macro, as well as Field Programmable Gate Array FPGA, the idea here is to provide a general EnDat interface module which has the ability of realizing serial encoder data acquisition (RS232/RS485) of EnDat interface. This paper introduces the design idea partly, focuses on methods of the hardware and software design. It was proved by experiments that this design could implement data acquisition.