用SPI总线将两块实验电路板连接起来。作为SPI主机的PIC单片机读取其所在的实验电路板上的按键值，判断6只按键中的哪一只被按下，并将按键的编号通过SPI总线发送给作为从机的PIC单片机。从机得到按键编号后点亮从机所在电路板上对应的发光二极管，并将受到的按键编号重新发还给主机，主机受到后也将所在电路板上对应的发光二极管点亮。-Two breadboard connection with the SPI bus. Read key value of its experimental circuit board as a the SPI host of PIC microcontroller to determine which six buttons is pressed only, and the key number is send as slave PIC microcontroller through the SPI bus. Lit from the machine to give the key number corresponding to the circuit board from the machine is located a light emitting diode, and by the key number is re-sent back to the host, the host will also be the subject for whom the circuit board corresponding to the light emitting diode is lighted.