From 8050813d32402336eabf43152dd0e0ef76a54247 Mon Sep 17 00:00:00 2001
From: Grumpy <dfouche8@gmail.com>
Date: Tue, 22 Jun 2021 08:12:39 +1200
Subject: [PATCH] =?UTF-8?q?=F0=9F=90=9B=20Fix=20dual=20Neopixels=20(#22174?=
 =?UTF-8?q?)?=
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---
 Marlin/src/feature/leds/neopixel.h     |  1 -
 Marlin/src/gcode/feature/leds/M150.cpp | 19 +++++++++++++------
 2 files changed, 13 insertions(+), 7 deletions(-)

diff --git a/Marlin/src/feature/leds/neopixel.h b/Marlin/src/feature/leds/neopixel.h
index e577948cd851..b2c16459f504 100644
--- a/Marlin/src/feature/leds/neopixel.h
+++ b/Marlin/src/feature/leds/neopixel.h
@@ -114,7 +114,6 @@ class Marlin_NeoPixel {
       #if CONJOINED_NEOPIXEL
         adaneo2.show();
       #else
-        IF_DISABLED(NEOPIXEL2_SEPARATE, adaneo1.setPin(NEOPIXEL2_PIN));
         adaneo1.show();
         adaneo1.setPin(NEOPIXEL_PIN);
       #endif
diff --git a/Marlin/src/gcode/feature/leds/M150.cpp b/Marlin/src/gcode/feature/leds/M150.cpp
index 5d175ea8f779..4d271007e56e 100644
--- a/Marlin/src/gcode/feature/leds/M150.cpp
+++ b/Marlin/src/gcode/feature/leds/M150.cpp
@@ -52,14 +52,16 @@
  *   M150 I1 R       ; Set NEOPIXEL index 1 to red
  *   M150 S1 I1 R    ; Set SEPARATE index 1 to red
  */
-
 void GcodeSuite::M150() {
   #if ENABLED(NEOPIXEL_LED)
-    const uint8_t index = parser.intval('I', -1);
+    const int8_t index = parser.intval('I', -1);
     #if ENABLED(NEOPIXEL2_SEPARATE)
-      const uint8_t unit = parser.intval('S'),
-                    brightness = unit ? neo2.brightness() : neo.brightness();
-      *(unit ? &neo2.neoindex : &neo.neoindex) = index;
+      int8_t brightness, unit = parser.intval('S', -1);
+      switch (unit) {
+        case -1: neo2.neoindex = index; // fall-thru
+        case  0:  neo.neoindex = index; brightness =  neo.brightness(); break;
+        case  1: neo2.neoindex = index; brightness = neo2.brightness(); break;
+      }
     #else
       const uint8_t brightness = neo.brightness();
       neo.neoindex = index;
@@ -75,10 +77,15 @@ void GcodeSuite::M150() {
   );
 
   #if ENABLED(NEOPIXEL2_SEPARATE)
-    if (unit == 1) { leds2.set_color(color); return; }
+    switch (unit) {
+      case 0: leds.set_color(color); return;
+      case 1: leds2.set_color(color); return;
+    }
   #endif
 
+  // If 'S' is not specified use both
   leds.set_color(color);
+  TERN_(NEOPIXEL2_SEPARATE, leds2.set_color(color));
 }
 
 #endif // HAS_COLOR_LEDS