键盘扫描程序，支持键盘阵列，支持按键消抖动，支持单个按键的单拍、连拍；以及组合键。键盘扫描函数用于在定时器中断中调用。-Keyboard scan module. Can scan the key matrix, support jitter eliminating, single key press down, continuous press, and composed keys. The scan function could be called in the ISR.