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.