From 1bac0c176518a13a320d7dd69d400f21902927c7 Mon Sep 17 00:00:00 2001
From: 3d-gussner <3d.gussner@gmail.com>
Date: Sat, 18 Apr 2020 16:39:04 +0200
Subject: [PATCH] Add dummy G21 to prevent UNKOWN warnings in serial And as
 Prusa firmware operates ONLY in milimeters it kind of does what G21 is
 supposed to do.

---
 Firmware/Marlin_main.cpp | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/Firmware/Marlin_main.cpp b/Firmware/Marlin_main.cpp
index e4e1e0b2..d6955f89 100755
--- a/Firmware/Marlin_main.cpp
+++ b/Firmware/Marlin_main.cpp
@@ -4276,6 +4276,14 @@ if(eSoundMode!=e_SOUND_MODE_SILENT)
       #endif //FWRETRACT
     
 
+    /*!
+	### G21 - Sets Units to Millimters <a href="https://reprap.org/wiki/G-code#G21:_Set_Units_to_Millimeters">G21: Set Units to Millimeters</a>
+	Units are in millimeters. Prusa doesn't support inches.
+    */
+    case 21: 
+      break; //Doing nothing. This is just to prevent serial UNKOWN warnings.
+    
+
     /*!
     ### G28 - Home all Axes one at a time <a href="https://reprap.org/wiki/G-code#G28:_Move_to_Origin_.28Home.29">G28: Move to Origin (Home)</a>
     Using `G28` without any parameters will perfom homing of all axes AND mesh bed leveling, while `G28 W` will just home all axes (no mesh bed leveling).