从板meg88检测有无按键按下，若有按键按下，触发meg16主板外部中断，开始spi通信，然后将按键值返回给meg88，并用键盘显示按下的按键值-From the board meg88 detect any key press, if button is pressed, the external interrupt trigger meg16 board began spi communication, and will be key to return to meg88, and pres