The design and implementation of universal interface circuit for photoelectric encoder

The majority of encoder signal process circuits only support one type of the specific photoelectric encoder, either absolute encoder or incremental encoder. In order to realize the compatibility for both two types of encoders simultaneously, a novel encoder signal process circuit based on FPGA is presented in this paper. Firstly, a series of universal functions are analyzed and demonstrated. On this basis, the approaches on multiplexing interfaces is designed and verified by simulation. Importantly, the compatibility is solved by multiplexing pins of the IC chip in terms of the hardware interface. As for the software interface, FPGA internal signal acquisition and processing programs deal with the different encoder protocols. Finally, two different types of encoders are concurrently connected to the circuit for system testing. The result indicates that the real-time angular position curve is smooth and the measured angle value is accurately displayed on the host computer. Consequently, the stability and compatibility are successfully proven. Besides, those expensive dedicated interface circuits could be replaced by the proposed circuit, as well as the costs can be significantly reduced. The circuit is ideal for applications requiring high resolution and fast data acquisition in industrial control fields.