From 232014cdd8176420389339e601c55594fa8db434 Mon Sep 17 00:00:00 2001
From: Mike <63822202+xsnoopy@users.noreply.github.com>
Date: Mon, 23 Aug 2021 20:03:54 -0400
Subject: [PATCH] Update README.md

Usually NC are connected from high voltage to the NC switch, then to the Input of a controll unit. For Microcontroller you need to wire it towards ground. This should help people to understand that better.
---
 README.md | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/README.md b/README.md
index 64c6bf9..6792cc6 100644
--- a/README.md
+++ b/README.md
@@ -3,7 +3,7 @@
 grblHAL has [many extensions](https://github.com/grblHAL/core/wiki) that may cause issues with some senders. As a workaround for these a [compile time option](https://github.com/grblHAL/core/wiki/Changes-from-grbl-1.1#workaround) has been added that disables extensions selectively. 
 
 __IMPORTANT!__ grblHAL defaults to normally closed \(NC\) switches for inputs, if none are connected when testing it is likely that the controller will start in alarm mode.  
-Temporarily short the Reset, E-Stop and Safety Door<sup>4</sup> inputs to ground or invert the corresponding inputs by setting `$14=73` to avoid that.  
+Temporarily short the Reset, E-Stop and Safety Door<sup>4</sup> inputs to ground or invert the corresponding inputs by setting `$14=73` to avoid that. Due to the internal pull up resistors on microcontroller the normally closed \(NC\) switches must be connected to GND and the coresponding input of the microcontroller.
 Please check out [this Wiki page](https://github.com/grblHAL/core/wiki/Changes-from-grbl-1.1) for additional important information.
 
 Windows users may try [ioSender](https://github.com/terjeio/Grbl-GCode-Sender), binary releases can be found [here](https://github.com/terjeio/Grbl-GCode-Sender/releases).