单片机SPI通信测试程序，使用SPI控制器读写SPI总线的外部设备-MCU SPI communication test program, the use of the the SPI controller read and write external SPI bus device

SPI(Serial Peripheral Interface--串行外设接口)总线系统是一种同步串行外设接口，它可以使MCU与各种外围设备以串行方式进行通信以交换信息。-SPI (Serial Peripheral Interface, Serial Peripheral Interface) bus system is a kind of synchronous Serial Peripheral Interface, it can make MCU communicate with a v