GRBL v1.1版本的限位开关连接
GRBL v1.1版本的限位开关连接wiki翻译
Wiring Limit Switches
Source websit:https://github.com/gnea/grbl/wiki/Wiring-Limit-Switches
The limit switchesare used to detect the physical limits of the working area and to position thehead in initial position during the homing process. Properly connected limitswitches can increase significantly the reliability of the GRBL - themicrocontroller pins connected to the switches are very vulnerable to anynoise.
限位开关使是用来给工作区域做物理限制和给原点回归提供初始位置用的，适当的方法连接限位开关可以提高Grbl的可靠性，因为单片机的引脚非常容易收到噪声干扰
Before starting,make sure your coordinate frame is setup properly on your CNC machine andsatisfies the right-hand rule. If you're not sure, its explained in the quicksetup guide here.Otherwise, you will likely encounter problems with the homing cycle, where itbehaves strangely. If you are having issues with the homing cycle, read this FAQ.
在此之前，确保你的CNC机器上的坐标系是设置正确并且满足右手定则，如果你不确定，你可以去快速安装指南中查看，除此之外，你也可能会遇到原点回归的问题，有些行为会有些奇怪，如果你有这些问题，你可以去FAQ里面阅读
There are twotypes of end switches wiring:
有两种限位开关的接线方式
Normally Opened end switches (NO) - switches are connected in parallel, if the head hits one of the switches the resistance becomes low (<10 Ohm). The wiring is simple but there is no indication if one of the switches is disconnected (broken wire).
常开型开关-开关是并联的，如果触头碰到一个开关，电平就会变低，这种连接是简单的，但是无法检测开关是否有断开
Normally Closed end switches (NC) - switches are connected in serial, if the head hits one of the switches the resistance become high (> 1 MOhm). The wiring is more complicated but if any of the switches is disconnected (broken wire) this will be immediately detected. This is the way how all professional CNC machines end switches were wired.
常闭型开关-开关是串联的，如果触头碰到一个开关电平就会变高，这种连接是比较复杂的，但是一旦有任何开关断开连接都将呗立刻检测到，这是现在许多数控机床使用的一种连接方法
The easiest way toattach limit switches to Arduino UNO is to just connect the switches to thecorresponding pins and to rely on the internal weak pull up resistors (~47K) ofthe ATMega328 chip. The Normal connected (NC) switch wiring is shown below:
有一种简答的arduino uno的限位开关连接方法就是依靠ATmega328内部的弱上拉电阻（~47K）直接连接到引脚上面，下面是常闭开关的接法
The Normal Open (NO) switch wiring is shown below:
下面是常开开关的接法
One improvement is to connect 1K to 4.7K pull up resistors to 5V and100nF capacitors to GND. The extra pull ups and capacitors have noticeablenoise suppression effect over the GRBL performance.
有一种改进的接法就是，外接一个4.7K的电阻到5v，接一个100nF的电容到GND，，额外的上拉电阻和电容有明显的一直噪声的作用
