Circuit for expanding digital I/O interface

The utility model discloses a circuit for expanding a digital I/O (Input/Output) interface. The circuit comprises a monitoring unit, an expansion input interface unit and an expansion output interface unit, wherein the extended input interface unit and the extended output interface unit are connected through an SPI (Serial Peripheral Interface) in the monitoring unit and are used for receiving and transmitting data. The circuit for expanding the digital I/O interface is simple in structure, data receiving and transmitting of the expansion input interface unit and the expansion output interface unit are realized by utilizing the SPI interface of the monitoring unit or adding the SPI interface in the monitoring unit in the circuit, and further unlimited expansion of the digital I/O interface in the circuit is realized. And the cost of expanding the digital I/O interface by the host is greatly reduced. 本实用新型公开了一种扩展数字I/O接口的电路，该电路包括：监控单元、扩展输入接口单元、扩展输出接口单元；其中，所述扩展输入接口单元、所述扩展输出接口单元通过所述监控单元中的SPI接口连接并进行数据接收和发送。本实用新型所述