摘要：Typically,a variety of digital devices are built into the *** digital devices in order to develop a variety of applications PC,various devices such as smart phones should be easily *** so far the interface of these devices has not been a unified approach. Development of various types of devices to easily shall be equipped with various interfaces such as UART,SPI,I2C. However,there follows a lot of hardware problems to greatly increasing the number of I/O *** I/O are four types based on the same *** port is controlled the software approach to operate UART,SPI, I2C,etc.