Limit Case Light PWM (#15459)

Marlin/Configuration_adv.h

@@ -379,6 +379,7 @@
   #define INVERT_CASE_LIGHT false             // Set true if Case Light is ON when pin is LOW
   #define CASE_LIGHT_DEFAULT_ON true          // Set default power-up state on
   #define CASE_LIGHT_DEFAULT_BRIGHTNESS 105   // Set default power-up brightness (0-255, requires PWM pin)
+  //#define CASE_LIGHT_MAX_PWM 128            // Limit pwm
   //#define CASE_LIGHT_MENU                   // Add Case Light options to the LCD menu
   //#define CASE_LIGHT_NO_BRIGHTNESS          // Disable brightness control. Enable for non-PWM lighting.
   //#define CASE_LIGHT_USE_NEOPIXEL           // Use Neopixel LED as case light, requires NEOPIXEL_LED.

Marlin/src/feature/caselight.cpp

@@ -71,7 +71,13 @@ void update_case_light() {
 
     #if DISABLED(CASE_LIGHT_NO_BRIGHTNESS)
       if (PWM_PIN(CASE_LIGHT_PIN))
-        analogWrite(pin_t(CASE_LIGHT_PIN), n10ct);
+        analogWrite(pin_t(CASE_LIGHT_PIN),
+          #if CASE_LIGHT_MAX_PWM == 255
+            n10ct
+          #else
+            map(n10ct, 0, 255, 0, CASE_LIGHT_MAX_PWM)
+          #endif
+        );
       else
     #endif
       {

Marlin/src/inc/Conditionals_post.h

@@ -1334,6 +1334,17 @@
   #define FAST_PWM_FAN_FREQUENCY ((F_CPU) / (2 * 255 * 1)) // Fan frequency default
 #endif
 
+/**
+ * MIN/MAX case light PWM scaling
+ */
+#if HAS_CASE_LIGHT
+  #ifndef CASE_LIGHT_MAX_PWM
+    #define CASE_LIGHT_MAX_PWM 255
+  #elif !WITHIN(CASE_LIGHT_MAX_PWM, 1, 255)
+    #error "CASE_LIGHT_MAX_PWM must be a value from 1 to 255."
+  #endif
+#endif
+
 /**
  * Bed Probe dependencies
  */