这是读取键盘的子程序

主要内容为：如何定义位，如何得到按键状态,防止键盘干扰的方法

以及如何处理读入的键值

思路：首先在某一引脚输出一个电平，然后读入引脚的电平，如果刚好相反

那么可能有按键发生，但是不排除干扰，为了防止干扰，需要软件延时20ms

消除干扰，然后，等待用户释放，否则，可能重复的到某种结果，发生意外情况

　　应该说键盘输入是单片机外部指令输入的重要途径，因此如何设计键盘以及键盘的工作原理、读键盘的方法、键盘的抗干扰设计等在单电能机系统设计中占有重要地位。这个例子在系统硬件的基础上设计了软件查询程序、软件延时程序（防止干扰），大致讲述了一种查询式键盘的工作原理与读取方式。 -This is the subroutine to read the keyboard

The main contents are: how to define, and how to get keys, and the methods to prevent interference with the keyboard

As well as how to deal with the key read

Ideas: First of all, the output of a pin in a certain level, and then read the pin level, if the opposite

Then the keys may have occurred, but does not rule out the interference, in order to prevent interference, the need for software 20ms delay

The elimination of interference, and then wait for the release of the user, otherwise, may be repeated to a certain result, the occurrence of unforeseen circumstances

It should be said that the external keyboard input is a single chip an important way to enter commands, so how to design the keyboard and the keyboard work of the principle of the method of reading the keyboard, the keyboard design of the anti-jamming power in a single machine system design plays an important role. This example hardware in the system based on the query d